1. J Clin Neurosci. 2009 Aug;16(8):1001-8.

Deep brain stimulation for Parkinson's disease: Australian referral guidelines.

Silberstein P, Bittar RG, Boyle R, Cook R, Coyne T, O'Sullivan D, Pell M, Peppard
R, Rodrigues J, Silburn P, Stell R, Watson P; Australian DBS Referral Guidelines 
Working Group.

Collaborators: Blackie J, Danks A, Iansek R, Kimber T, Krause M, Lind C, Mahant
N, McDonald M, McNeill P, Owler B, Parasivam S, Rosenfeld J, Thompson P, Tisch S,
Thyagarajnan D, Whyte S, Wilcox R, Williams D.

North Shore Private Hospital, Sydney, New South Wales, Australia.
paul@silberstein.com.au

The advent of deep brain stimulation (DBS) has been an important advance in the
treatment of Parkinson's disease (PD). DBS may be employed in the management of
medication-refractory tremor or treatment-related motor complications, and may
benefit between 4.5% and 20% of patients at some stage of their disease course.
In Australia, patients with PD are reviewed by specialised DBS teams who assess
the likely benefits and risks associated with DBS for each individual. The aim of
these guidelines is to assist neurologists and general physicians identify
patients who may benefit from referral to a DBS team. Common indications for
referral are motor fluctuations and/or dyskinesias that are not adequately
controlled with optimised medical therapy, medication-refractory tremor, and
intolerance to medical therapy. Early referral for consideration of DBS is
recommended as soon as optimised medical therapy fails to offer satisfactory
motor control.

PMID: 19596113 [PubMed - indexed for MEDLINE]


2. Brain. 2009 Aug;132(Pt 8):2151-60. Epub 2009 May 11.

Gait freezing in Parkinson's disease and the stride length sequence effect
interaction.

Chee R, Murphy A, Danoudis M, Georgiou-Karistianis N, Iansek R.

School of Psychology, Psychiatry and Psychological Medicine, Monash University,
Clayton, Victoria, Australia.

Freezing of gait (FOG) has been identified as one of the main contributors to
gait disturbances in Parkinson's disease. While the pathophysiology remains
enigmatic, several factors such as step length and the sequence effect (step to
step reduction in amplitude) may lead to the occurrence of FOG. It was
hypothesized that by reducing step length, FOG episodes would present more
frequently if a significant sequence effect (measured as a regression slope) was 
co-existent in the subject. Twenty-six participants with Parkinson's disease were
separated clinically into a freezing (PD + FOG, n = 16) and non-freezing (PD-FOG,
n = 10) group, with 10 age-matched control participants. Testing involved walking
trials where preferred step length was set at 100%, 75%, 50% and 25% of
normalized step length. The number of FOG episodes increased in the 50% condition
and further increased in the 25% condition compared to other conditions. The
participants with FOG also demonstrated a larger average regression slope, with
significant differences in the 75%, 50% and 25% conditions when compared to the
PD-FOG and control groups. There were no significant differences when comparing
the slope of the PD-FOG and control group, indicating the reduced step length and
the sequence effect may have led to the occurrence of FOG. These findings support
the possible dual requirement of a reduced step length and a successive step to
step amplitude reduction to lead to FOG.

PMID: 19433440 [PubMed - indexed for MEDLINE]


3. BMC Geriatr. 2009 Jan 20;9:2.

Quantifying the profile and progression of impairments, activity, participation, 
and quality of life in people with Parkinson disease: protocol for a prospective 
cohort study.

Morris ME, Watts JJ, Iansek R, Jolley D, Campbell D, Murphy AT, Martin CL.

School of Physiotherapy, The University of Melbourne, Melbourne, VIC 3010,
Australia. m.morris@unimelb.edu.au

BACKGROUND: Despite the finding that Parkinson disease (PD) occurs in more than
one in every 1000 people older than 60 years, there have been few attempts to
quantify how deficits in impairments, activity, participation, and quality of
life progress in this debilitating condition. It is unclear which tools are most 
appropriate for measuring change over time in PD. METHODS AND DESIGN: This
protocol describes a prospective analysis of changes in impairments, activity,
participation, and quality of life over a 12 month period together with an
economic analysis of costs associated with PD. One-hundred participants will be
included, provided they have idiopathic PD rated I-IV on the modified Hoehn &
Yahr (1967) scale and fulfil the inclusion criteria. The study aims to determine 
which clinical and economic measures best quantify the natural history and
progression of PD in a sample of people receiving services from the Victorian
Comprehensive Parkinson's Program, Australia. When the data become available, the
results will be expressed as baseline scores and changes over 3 months and 12
months for impairment, activity, participation, and quality of life together with
a cost analysis. DISCUSSION: This study has the potential to identify baseline
characteristics of PD for different Hoehn & Yahr stages, to determine the
influence of disease duration on performance, and to calculate the costs
associated with idiopathic PD. Valid clinical and economic measures for
quantifying the natural history and progression of PD will also be identified.
TRIAL REGISTRATION: ACTRN12609000008224.

PMCID: 2649133
PMID: 19152709 [PubMed - indexed for MEDLINE]


4. Mov Disord. 2009 Jan 15;24(1):64-71.

A randomized controlled trial of movement strategies compared with exercise for
people with Parkinson's disease.

Morris ME, Iansek R, Kirkwood B.

School of Physiotherapy, The University of Melbourne, Australia.
m.morris@unimelb.edu.au

This randomized controlled clinical trial was conducted to compare the effects of
movement rehabilitation strategies and exercise therapy in hospitalized patients 
with idiopathic Parkinson's disease. Participants were randomly assigned to a
group that received movement strategy training or musculoskeletal exercises
during 2 consecutive weeks of hospitalization. The primary outcome was disability
as measured by the Unified Parkinson's Disease Rating Scale, UPDRS (motor and ADL
components). Secondary outcomes were balance, walking speed, endurance, and
quality of life. Assessments were carried out by blinded testers at baseline,
after the 2 weeks of treatment and 3 months after discharge. The movement
strategy group showed improvements on several outcome measures from admission to 
discharge, including the UPDRS, 10 m walk, 2 minute walk, balance, and PDQ39.
However, from discharge to follow up there was significant regression in
performance on the 2 minute walk and PDQ39. For the exercise group, quality of
life improved significantly during inpatient hospitalization and this was
retained at follow-up. Inpatient rehabilitation produces short term reductions in
disability and improvements in quality of life in people with Parkinson's
disease.

PMID: 18942100 [PubMed - indexed for MEDLINE]


5. BMC Geriatr. 2008 Sep 30;8:23.

Cost effectiveness of preventing falls and improving mobility in people with
Parkinson disease: protocol for an economic evaluation alongside a clinical
trial.

Watts JJ, McGinley JL, Huxham F, Menz HB, Iansek R, Murphy AT, Waller ER, Morris 
ME.

Centre for Health Economics, Monash University, Building 75, 3800 Melbourne,
Australia. jenny.watts@buseco.monash.edu.au

BACKGROUND: Cost of illness studies show that Parkinson disease (PD) is costly
for individuals, the healthcare system and society. The costs of PD include both 
direct and indirect costs associated with falls and related injuries. METHODS:
This protocol describes a prospective economic analysis conducted alongside a
randomised controlled trial (RCT). It evaluates whether physical therapy is more 
cost effective than usual care from the perspective of the health care system.
Cost effectiveness will be evaluated using a three-way comparison of the cost per
fall averted and the cost per quality adjusted life year saved across two
physical therapy interventions and a control group. CONCLUSION: This study has
the potential to determine whether targetted physical therapy as an adjunct to
standard care can be cost effective in reducing falls in people with PD. TRIAL
REGISTRATION: No: ACTRN12606000344594.

PMCID: 2573876
PMID: 18823565 [PubMed - indexed for MEDLINE]


6. Mov Disord. 2008;23 Suppl 2:S451-60.

Gait festination and freezing in Parkinson's disease: pathogenesis and
rehabilitation.

Morris ME, Iansek R, Galna B.

School of Physiotherapy, The University of Melbourne, Australia.
m.morris@unimelb.edu.au

Erratum in:
    Mov Disord. 2008 Aug 15;23(11):1639-40.

Freezing and festination during gait are common yet poorly understood motor
control deficits in people with Parkinson's disease (PD). As a basis for evidence
based clinical decision making during rehabilitation, we explore the underlying
factors associated with freezing of gait in PD. It is argued that disorders of
motor set and the sequence effect (festination) are associated with freezing,
either in isolation or in combination. The contribution of environmental
constraints, task related factors, attention, mental status, and prolonged use of
PD medications are also investigated. On the basis of these findings, we propose 
strategies to reduce the frequency and severity of freezing episodes for a range 
of locomotion tasks. (c) 2008 Movement Disorder     Society.

PMID: 18668618 [PubMed - indexed for MEDLINE]


7. Mov Disord. 2008 Jul 30;23(10):1391-7.

Head and trunk rotation during walking turns in Parkinson's disease.

Huxham F, Baker R, Morris ME, Iansek R.

Centre for Clinical Research Excellence in Gait Analysis and Gait Rehabilitation,
Victoria, Australia. fhuxham@bigpond.net.au

Head and trunk axial rotation during walking to align with a new path are
integral components of direction change (turning). Turning is problematic in
people with Parkinson's disease (PD), who appear to move en-bloc when turning and
when walking straight. Axial rotation has been little investigated in this group.
Accordingly, head, thorax, and pelvis rotation relative to the laboratory axes
(global rotation) was investigated in 10 patients with PD and 10 matched
comparison subjects when walking straight and when turning 60 and 120 degrees .
Data were selected at three footfalls before and three after a pole denoting the 
corner. Although rotation was reduced overall in patients with PD, final
differences were minimized by rotation commencing at an earlier step in the
patient group. When rotation was measured at various distances relative to the
corner, the patient group demonstrated greater rotation than their peers. In
support of clinical observations, patients constrained thorax and pelvis closely 
together around the corner, while control subjects maintained a pattern of
reciprocal oscillation when turning. Stride length reduction appears to
contribute more to inefficient turning in PD than under-scaled amplitude of
rotation. Copyright 2008 Movement Disorder     Society.

PMID: 18528897 [PubMed - indexed for MEDLINE]


8. Mov Disord. 2008 Apr 30;23(6):817-23.

Footstep adjustments used to turn during walking in Parkinson's disease.

Huxham F, Baker R, Morris ME, Iansek R.

Centre for Clinical Research Excellence in Gait Analysis and Gait Rehabilitation,
Victoria, Australia. fhuxham@bigpond.net.au

Turning during walking is frequently problematic in Parkinson's disease (PD). The
spatiotemporal characteristics of footstep adjustments used to turn 60 and 120
degrees were examined in 10 people with PD and 10 age, gender- and height-matched
control subjects, using three-dimensional motion analysis. Control subjects used 
a recognizable pattern of spatial and temporal footstep modulations to turn.
Participants with PD demonstrated significant differences in almost all
variables. They (1) failed to turn as far as their peers; (2) showed a similar
but scaled-down pattern of spatial adjustments to turn; (3) used shorter strides 
when walking, with exaggerated reductions when turning; and (4) demonstrated
small but significant temporal differences in step time adjustments. Group
differences were more marked for the larger turn. Spatial results, interpreted in
light of hypothesized basal ganglia dysfunction, are consistent with a normal
motor command but impaired ability to maintain movement amplitude. Differences in
adjustment of step time to turn may reflect impaired locomotor timing control in 
subjects with PD during challenging gait tasks. (c) 2008 Movement Disorder    
Society.

PMID: 18200603 [PubMed - indexed for MEDLINE]


9. Mov Disord. 2008 Mar 15;23(4):574-80.

For better or worse: The effect of levodopa on speech in Parkinson's disease.

Ho AK, Bradshaw JL, Iansek R.

Department of Psychology, School of Psychology and Clinical Language Sciences,
University of Reading, Reading, United Kingdom. aileenkho@netscape.net

While the beneficial effect of levodopa on traditional motor control tasks have
been well documented over the decades, its effect on speech motor control has
rarely been objectively examined and the existing literature remains
inconclusive. This paper aims to examine the effect of levodopa on speech in
patients with Parkinson's disease. It was hypothesized that levodopa would
improve preparatory motor set related activity and alleviate hypophonia. Patients
fasted and abstained from levodopa overnight. Motor examination and speech
testing was performed the following day, pre-levodopa during their "off" state,
then at hourly intervals post-medication to obtain the best "on" state. All
speech stimuli showed a consistent tendency for increased loudness and faster
rate during the "on" state, but this was accompanied by a greater extent of
intensity decay. Pitch and articulation remained unchanged. Levodopa effectively 
upscaled the overall gain setting of vocal amplitude and tempo, similar to its
well-known effect on limb movement. However, unlike limb movement, this effect on
the final acoustic product of speech may or may not be advantageous, depending on
the existing speech profile of individual patients. (c) 2007 Movement Disorder    
Society.

PMID: 18163453 [PubMed - indexed for MEDLINE]


10. Mov Disord. 2006 Dec;21(12):2096-100.

Effect of a concurrent task on driving performance in people with Parkinson's
disease.

Stolwyk RJ, Triggs TJ, Charlton JL, Moss S, Iansek R, Bradshaw JL.

Department of Psychology, Monash University, Melbourne, Australia.

Numerous studies previously have reported reduced driving performance in people
with Parkinson's disease (PD). Few studies to date, however, have examined how
specific cognitive difficulties associated with PD impact on specific aspects of 
driving performance in this population. In this study, the impact of a concurrent
task on driving performance was examined. A simulator was used to measure the
driving behavior of 18 current drivers with PD and 18 matched controls. The
presence of a concurrent task was manipulated between conditions. Results showed 
that, although groups were similarly affected by the concurrent task on most
driving measures, participants with PD were disproportionately affected on
operational level driving behavior. It also appears that participants with PD
sacrificed concurrent task performance to maintain driving performance. These
results further support the hypothesis that cognitive difficulties associated
with PD compromise driving performance in this population, even in the mild to
moderate stages of the disease. Copyright 2006 Movement Disorder     Society.

PMID: 17013911 [PubMed - indexed for MEDLINE]


11. J Clin Exp Neuropsychol. 2006 Aug;28(6):898-913.

Neuropsychological function and driving ability in people with Parkinson's
disease.

Stolwyk RJ, Charlton JL, Triggs TJ, Iansek R, Bradshaw JL.

Department of Psychology, Monash University, Victoria, Australia.

In this study the association between cognitive symptoms of PD and driving
performance was investigated by examining the correlation between
neuropsychological test performance and driving simulator behavior. Eighteen
participants with PD and 18 healthy participants in a matched comparison group
completed a range of neuropsychological measures. These data were correlated with
driving simulator performance results from an earlier study. Significant
correlations were found between several measures of neuropsychological test
performance and driving behavior in participants with PD. In contrast, few
significant correlations were obtained in the comparison group. Results suggest
that executive difficulties in people with PD such as working memory, planning
and set shifting are associated with reduced tactical level driving performance
such as speed adaptation and complex curve navigation. Impaired information
processing, visual attention and visual perception in people with PD appears
associated with reduced operational level driving performance, such as reacting
to road obstacles and maintaining constant lane position. Few correlations were
found between measures of physical mobility and psychomotor speed with driving
measures. Overall, this study highlights the important role of cognitive function
in driving performance within the PD population. Comprehensive assessment of
cognitive function should be included when assessing driving competency in people
with PD.

PMID: 16822731 [PubMed - indexed for MEDLINE]


12. Mov Disord. 2006 Sep;21(9):1419-24.

The sequence effect and gait festination in Parkinson disease: contributors to
freezing of gait?

Iansek R, Huxham F, McGinley J.

Geriatric Research Unit, Kingston Centre Southern Health, Melbourne, Australia.

Festination and freezing of gait (FOG) are poorly understood gait disorders that 
cause disability and falls in people with Parkinson disease (PD). In PD, basal
ganglia malfunction leads to motor set deficits (hypokinesia), while altered
motor cue production leads to a sequence effect, whereby movements becomes
progressively smaller as in festination. We suggest both factors may contribute
to FOG. Disturbance of set maintenance by the basal ganglia in PD has previously 
been examined in gait, but limited systematic evaluation of the sequence effect
exists. In this study, we investigated the step-to-step amplitude relationship in
10 PD subjects with clinical evidence of festination and FOG. Four conditions
were examined: off levodopa, off with attentional strategies, off with visual
cues, and on levodopa. Participants demonstrated a sequence effect (F = 6.24; P =
0.001), which was reversed only by use of visual cues. In contrast, medication,
attentional strategies, and visual cues all improved hypokinesia. Variability was
marked both within and between participants in all conditions. The variability of
FOG is suggested to relate to a combination of factors, including the sequence
effect and its variability, as well as the severity of hypokinesia and its
response to medications. (c) 2006 Movement Disorder     Society.

PMID: 16773644 [PubMed - indexed for MEDLINE]


13. Mov Disord. 2005 Jul;20(7):846-57.

Impact of internal versus external cueing on driving performance in people with
Parkinson's disease.

Stolwyk RJ, Triggs TJ, Charlton JL, Iansek R, Bradshaw JL.

Department of Psychology, Monash University, Melbourne, Australia.
rene.stolwyk@med.monash.edu

Numerous aspects of driving performance seem compromised in people with
Parkinson's disease (PD). Measures of cognitive impairment consistently correlate
with poor driving simulator performance in this population; however, the effects 
of specific cognitive difficulties on discrete aspects of driving behavior have
not been investigated thoroughly. Previous studies have demonstrated that people 
with PD exhibit difficulties internally cueing cognitive processes. This study
examined the impact of impaired internal cueing on specific driving behaviors. A 
simulator measured the driving behavior of 18 current drivers in the
mild-to-moderate stages of PD and 18 matched controls. Participants navigated
through different driving conditions where the opportunity to use internal and
external cues was manipulated. People with PD exhibited difficulties using
internal cues to regulate driving behavior around traffic signals and curves.
Instead of using internal cues, participants with PD were more reliant on
external cues to regulate driving behavior. They were also less able to adapt
their driving behavior to suit driving conditions. Because all participants with 
PD were current drivers in the mild-to-moderate stages of the disease, findings
challenge the widely-held assumption that cognitive difficulties only impact on
driving performance in the moderate-to-severe stages of PD. Copyright 2005
Movement Disorder     Society.

PMID: 15747369 [PubMed - indexed for MEDLINE]


14. Mov Disord. 2005 Jan;20(1):40-50.

Three-dimensional gait biomechanics in Parkinson's disease: evidence for a
centrally mediated amplitude regulation disorder.

Morris M, Iansek R, McGinley J, Matyas T, Huxham F.

School of Physiotherapy, Faculty of Health Sciences, La Trobe University,
Melbourne, Victoria, Australia. m.morris@latrobe.edu.au

We examined whether people with Parkinson's disease (PD) have a central amplitude
regulation disorder using three-dimensional (3-D) gait analyses to compare the
effects of medication and attentional strategies on gait in 12 PD subjects and 12
matched comparison subjects. Subjects with PD first performed several 10-m gait
trials at preferred speed while off levodopa. They then walked at preferred speed
on levodopa; off levodopa with cues; and on levodopa with cues. Control subjects 
walked at preferred speed and then with visual cues to match their stride length 
to PD values. As well as spatiotemporal footstep data, pelvic and lower limb
kinematic profiles and angle-angle diagrams were produced for sagittal, coronal, 
and transverse plane movements using a 3-D motion analysis system. In people with
PD, decreased step length was accompanied by reduced movement amplitude across
all lower limb joints, in all movement planes. When control subjects were
required to walk with short steps matched to the size of PD comparisons, they
displayed a similar multijoint reduction in amplitude. For PD subjects, both
levodopa and visual cues increased movement amplitude across all lower limb
joints. Amplitude increased further when levodopa and visual cues were combined, 
resulting in normalization of step length. This finding suggested that reduced
step length is due to a mismatch between cortically selected movement amplitude
and basal ganglia maintenance mechanisms. Levodopa and cues normalized amplitude 
across all joints by altering motor set and bypassing defective basal ganglia
mechanisms. (c) 2004 Movement Disorder     Society.

PMID: 15390033 [PubMed - indexed for MEDLINE]


15. J Clin Exp Neuropsychol. 2003 May;25(3):361-75.

Dual target identification and the attentional blink in Parkinson's disease.

Vardy Y, Bradshaw JL, Iansek R.

Department of Psychology, Monash University, Clayton, Victoria, Australia.

In healthy adults, deficits in identifying a second target following a previously
attended target in Rapid Serial Visual Presentation (RSVP) occur between
intertarget intervals of approximately 100-500 ms. This Attentional Blink (AB) is
investigated in nondemented medicated Parkinson's patients using a modification
of the standard paradigm that required the identification of two red letters
embedded in a black letter distractor stream. Parkinson's patients and controls
produced an equivalent AB, although with a different pattern of errors. Thus, the
processing and clearance of information was largely preserved in nondemented
Parkinson's patients, without evidence of bradyphrenia. However, perseveration of
earlier RSVP items in short-term memory was thought to explain the different
pattern of errors.

PMID: 12916649 [PubMed - indexed for MEDLINE]


16. Phys Ther. 2002 Sep;82(9):888-97.

Dual task interference during gait in people with Parkinson disease: effects of
motor versus cognitive secondary tasks.

O'Shea S, Morris ME, Iansek R.

Wodonga Regional Health Service, Wodonga, Victoria, Australia.

BACKGROUND AND PURPOSE: Exacerbation of movement disorders while doing 2 tasks
(dual task performance) is a characteristic feature of Parkinson disease (PD).
The aim of this investigation was to identify whether the type of secondary task 
(motor or cognitive) determined the severity of dual task interference. SUBJECTS 
AND METHODS: Footstep patterns for 15 people with PD and 15 comparison subjects
without PD were compared when they walked: (1) at a self-selected speed, (2)
while simultaneously performing a motor task (coin transference), and (3) while
simultaneously performing a cognitive task (digit subtraction). Gait speed,
stride length, cadence, and the percentage of the gait cycle in double-limb
stance (DS) were examined with a computerized stride analyzer. RESULTS: When
there was no second task, the mean stride length was less in the group with PD
(1.29 m) than in the comparison group (1.51 m), and the mean gait speed was less 
in the group with PD (71.47 m/min) than in the comparison group (87.29 m/min).
The mean cadence was less in the group with PD (110.79 steps/min) than in the
comparison group (115.81 steps/min). The percentage of the gait cycle in DS was
greater in the group with PD (33.38%) than in the comparison group (31.21%). Both
groups reduced their stride length and speed when they had to change from unitask
performance to dual task performance and DS increased. For the group with PD,
cadence also decreased. For both groups, the type of secondary task had a
negligible effect on the performance decrement. DISCUSSION AND CONCLUSION:
Although the performance of simultaneous motor or cognitive tasks compromised
gait in people with PD, the type of secondary task was not a major determinant of
the severity of dual task interference.

PMID: 12201803 [PubMed - indexed for MEDLINE]


17. Med J Aust. 2002 Aug 5;177(3):142-6.

Deep brain stimulation of the subthalamic nucleus in Parkinson's disease.

Iansek R, Rosenfeld JV, Huxham FE.

Movement Disorders Program, Kingston Centre, Victoria, Australia.
iansek@ozemail.com.au

Comment in:
    Med J Aust. 2002 Aug 5;177(3):125-6.

OBJECTIVE: To evaluate the effects of bilateral deep brain stimulation in the
subthalamic nucleus for symptomatic relief of advanced idiopathic Parkinson's
disease. DESIGN: Prospective cohort study. SETTING: Patients were assessed and
received medical treatment at the Kingston Centre, Southern Health, Melbourne.
Surgery took place at Melbourne Neuroscience Centre, The Royal Melbourne
Hospital. Both are tertiary public institutions. SUBJECTS: 14 patients with
Parkinson's disease with intact cognition and difficult to manage motor symptoms 
who were referred to Kingston Centre between 1996 and 2000 and were eligible for 
surgical intervention. INTERVENTIONS: All patients were assessed both after 12
hours' withdrawal from and while taking their levodopa medication on two
occasions before surgery. Further assessments were carried out one, three, six
and 12 months after surgery. MAIN OUTCOME MEASURES: The Unified Parkinson's
Disease Rating Scale motor exam and gait parameters, such as stride length and
velocity, were compared at six months after surgery with neither stimulation nor 
medication, with stimulation only, with medication only, and with stimulation and
medication. RESULTS: Stimulators were explanted in one patient after intracranial
haemorrhage and relocated to the thalamus in a second. Extraneous factors
prevented two patients from attending at six-month follow-up. Motor performance
improved significantly with stimulation alone in the 10 remaining patients.
Further significant gains were seen with stimulation and medication combined,
with an apparent reduction in side-effects such as dyskinesia. CONCLUSIONS:
Bilateral deep brain stimulation of the subthalamic nucleus significantly
improves motor performance in advanced Parkinson's disease, despite a rather high
complication rate.

PMID: 12149083 [PubMed - indexed for MEDLINE]


18. J Clin Exp Neuropsychol. 2002 Feb;24(1):36-47.

The effect of a concurrent task on Parkinsonian speech.

Ho AK, Iansek R, Bradshaw JL.

Neuropsychology Research Unit, Psychology Department, Monash University, Clayton 
3168, Vic, Australia. aileenkho@netscape.com

The aim of the study was to examine the role of attention in Parkinsonian speech 
control, by using a dual-task paradigm. Whilst it is well-known that skeletal
motor performance is impaired when Parkinson's disease (PD) patients are required
to perform two motor acts simultaneously, this has not been examined in the
context of speech motor control. Fifteen idiopathic PD patients and matched
controls performed two speech tasks (spontaneous conversation and numerical
recitation), with and without simultaneous engagement on a visuo-manual tracking 
task. Volumetric and temporal parameters of speech control were examined. The
findings show a trend towards reduced overall speech volume, and a significant
increase in progressive volume decay for patients relative to controls, for the
concurrent task condition. Patients' speech was also characterised by increased
speech initiation time and pause time, while speech rate was reduced upon
introduction of the concurrent task. Performance on the visuo-motor task by
patients, however, was similar to that of controls. The PD patients demonstrated 
a deterioration of volumetric and temporal measures of speech motor control, when
attentional resources were reduced by a distractor task. Consistent with
dual-task studies of skeletal movement control, these findings also show that
there is a Parkinsonian disadvantage for the more automatic and non-visually
controlled task, that is, speech, in the present study. It is, therefore,
suggested that speech and skeletal movement control are similarly driven by the
higher-order frontostriatal impairment inherent in PD.

PMID: 11935422 [PubMed - indexed for MEDLINE]


19. Clin Biomech (Bristol, Avon). 2001 Jul;16(6):459-70.

The biomechanics and motor control of gait in Parkinson disease.

Morris ME, Huxham F, McGinley J, Dodd K, Iansek R.

School of Physiotherapy, La Trobe University, Bundoora 3086, Australia.
m.morris@latrobe.edu.au

Parkinson disease is a progressive neurological condition characterised by
hypokinesia (reduced movement), akinesia (absent movement), tremor, rigidity and 
postural instability. These movement disorders are associated with a slow
short-stepped, shuffling gait pattern. Analysis of the biomechanics of gait in
response to medication, visual cues, attentional strategies and neurosurgery
provides insight into the nature of the motor control deficit in Parkinson
disease and the efficacy of current therapeutic interventions. In this article we
supplement a critical evaluation of the Parkinson disease gait literature with
two case examples. The first case describes the kinematic gait response of an
individual with Parkinson disease to visual cues in the "off" phase of the
levodopa medication cycle. The second case investigates the biomechanics and
motor control of turning during walking in a patient with Parkinson disease
compared with elderly and young control subjects. The results are interpreted in 
light of the need for gait analysis to investigate complex functional walking
tasks rather than confining assessment to straight line walking, which has been
the trend to date.

PMID: 11427288 [PubMed - indexed for MEDLINE]


20. Neuropsychiatry Neuropsychol Behav Neurol. 2001 Apr-Jun;14(2):109-16.

Motor instability in parkinsonian speech intensity.

Ho AK, Iansek R, Bradshaw JL.

Psychology Department, Monash University, Clayton, Victoria, Australia.
akh26@cam.ac.uk

OBJECTIVE: This study examined progressive speech intensity decay using two
speech tasks: sustained vowel phonation (Experiment 1) and sentence reading
(Experiment 2). BACKGROUND: Parkinsonian speech intensity has often been
clinically observed to fade out or trail off. This gradual diminution of
intensity is not unlike the well-documented progressive reduction of force
underlying (upper limb) micrographic parkinsonian handwriting and (lower limb)
marche à petit pas. Motor instability in speech intensity has yet to be
investigated in a controlled experimental setting, however. METHOD: Thirteen
Parkinson disease (PD) patients and their matched controls participated in
Experiment 1: data from 6 PD patients and controls who naturally (i.e., without
prior instruction) read the target sentence within a breath span were included in
the analysis for Experiment 2. Participants were instructed to inhale maximally
before vocalizing, and the extent of intensity declination over the breath span
was measured. RESULTS: Parkinson disease patients demonstrated a consistently
greater level of progressive intensity decay compared with matched controls for
both speech tasks. This successful documentation and analysis of fading speech
was interpreted as evidence for motor instability within the speech motor system 
in PD. CONCLUSIONS: It was concluded that the control of force in complex motor
sequences involving speech and limb movement is affected by a common deficit in
the frontostriatal circuit.

PMID: 11417664 [PubMed - indexed for MEDLINE]


21. Adv Neurol. 2001;87:347-61.

Gait disorders and gait rehabilitation in Parkinson's disease.

Morris ME, Huxham FE, McGinley J, Iansek R.

School of Physiotherapy, La Trobe University, Bundoora, 3086, Australia.

PMID: 11347239 [PubMed - indexed for MEDLINE]


22. Phys Ther. 2001 Feb;81(2):810-8.

Reliability of measurements obtained with the Timed "Up & Go" test in people with
Parkinson disease.

Morris S, Morris ME, Iansek R.

School of Physiotherapy, La Trobe University, Victoria, Australia.
m.morris@latrobe.edu.au

BACKGROUND AND PURPOSE: The Timed "Up & Go" Test (TUG) is used to measure the
ability of patients to perform sequential locomotor tasks that incorporate
walking and turning. This study investigated the retest reliability, interrater
reliability, and sensitivity of scores obtained with the TUG in detecting changes
in mobility in subjects with idiopathic Parkinson disease (PD). SUBJECTS: The
performance of 12 people with PD was compared with that of 12 age-matched
comparison subjects without PD. METHODS: The subjects with PD completed 5 trials 
of the TUG after withdrawal of levodopa for 12 hours ("off" phase of the
medication cycle) as well as an additional 5 trials 1 hour after levodopa was
administered ("on" phase of the medication cycle). They were scored on the
Modified Webster Scale at both sessions. The comparison subjects also performed 5
TUG trials. All trials were videotaped and timed by 2 experienced raters. The
videotape was later rated by 3 experienced clinicians and 3 inexperienced
clinicians. RESULTS: For the subjects with PD, within-session performance was
highly consistent, with correlations (r) ranging from.80 to.98 for the "off"
phase and from.73 to.99 for the "on" phase. The performance of the comparison
subjects across the 5 trials was also highly consistent (r=.90-.97). Comparisons 
showed differences between trials 1 and 2 on the TUG for both groups. Removal of 
data for trial 1 (the practice trial) further enhanced retest reliability. There 
was close agreement in TUG scores among raters despite different levels of
experience (intraclass correlation coefficient [3,1]=.87-.99). Mean TUG scores
were different between the "on" and "off" phases of the levodopa cycle and
between subjects with PD and comparison subjects during the "on" phase.
CONCLUSION AND DISCUSSION: Retest reliability and interrater reliability of the
TUG measurements were high, and the measurements reflected changes in performance
according to levodopa use. The TUG can also be used to detect differences in
performance between people with PD and elderly people without PD.

PMID: 11175678 [PubMed - indexed for MEDLINE]


23. Gait Posture. 2000 Dec;12(3):205-16.

Postural instability in Parkinson's disease: a comparison with and without a
concurrent task.

Morris M, Iansek R, Smithson F, Huxham F.

School of Physiotherapy, La Trobe University, 3083, Bundoora, Australia.
memorris@ozemail.com.au

The purpose of this investigation was to determine the effects of dual task
performance on postural instability in subjects with idiopathic Parkinson's
disease (PD) compared with healthy elderly people. In particular, we aimed to
divert attention to a secondary task so the full extent of balance disturbance
could be revealed without compensation by attentional mechanisms. Forty-five
subjects were tested: 15 PD subjects with a past history of falls; 15 PD subjects
with no history of falls; and 15 unimpaired individuals. Groups were matched for 
age and sex and subjects with PD were tested at peak dose in the levodopa
medication cycle. Each subject was tested on their ability to maintain stability 
in three conditions: (1) steady standing (feet apart, feet together, step stance,
tandem stance, single leg stance); (2) in response to perturbations generated by 
self-initiated movements (arm raise test, step test); and (3) in response to an
unexpected external perturbation in upright stance, the shoulder tug test. The
concurrent task was verbal-cognitive and required subjects to recite the days of 
the week backwards. The concurrent task produced a significant deterioration in
performance for the arm raise test in all groups, the step test for the PD
fallers and controls and for tandem stance in the PD fallers. Ceiling effects
were evident for timed tests with feet apart and feet together resulting in poor 
discriminative validity for these tests. The external perturbation test showed
differences between the three groups for both unitask and concurrent task
conditions, yet similar rates of change from unitask to dual task conditions.
Because PD fallers had a more severe initial deficit than controls, deterioration
placed them in that part of the balance continuum at high risk of losing
equilibrium.

PMID: 11154931 [PubMed - indexed for MEDLINE]


24. Neuropsychologia. 1999 Dec;37(13):1453-60.

Speech volume regulation in Parkinson's disease: effects of implicit cues and
explicit instructions.

Ho AK, Bradshaw JL, Iansek R, Alfredson R.

Psychology Department, Monash University, Clayton, Victoria, Australia.
aileen.ho@sci.monash.edu.au

This study examined the regulation of speech volume in hypophonic subjects with
Parkinson's disease (PD) and age- and gender-matched controls. The first two
experiments investigated the ability of subjects with PD to automatically
regulate speech volume in response to two types of implicit cue: (i) background
noise (BGN) and (ii) instantaneous auditory feedback (IAF). Control subjects
demonstrated the Lombard effect by automatically speaking louder when competing
against increasing levels of background noise. They also showed the reverse
effect, decreasing speech volume when increasing levels of facilitative
instantaneous auditory feedback were provided. Subjects with PD demonstrated
decreased overall speech volume; they were less able than controls to
appropriately increase volume as background noise increased, and to decrease
volume as IAF increased. Thus, subjects with PD demonstrated over-constancy of
speech volume and failed to respond to the implicit cues integral to volumetric
scaling. A further experiment (3) was carried out to contrast the regulation of
volume in response to implicit cue with an explicit attention-driven cue (i.e.
instructions regarding volume level). As in Experiments 1 and 2, subjects with PD
exhibited reduced speech volume. Under explicit volume instructions, the ability 
of subjects with PD to regulate volume was normalised. These findings suggest
that subjects with PD have the capacity to speak with normal volume provided they
consciously attend to speaking loudly. In subjects with PD, overall speech volume
was always lower than for control subjects, suggesting a reduction of cortical
motor set in the articulatory system similar to that demonstrated by the reduced 
amplitude of limb movements (hypokinesia) in the motor system.

PMID: 10617265 [PubMed - indexed for MEDLINE]


25. Aust Fam Physician. 1999 Sep;28(9):897-901.

Key points in the management of Parkinson's disease.

Iansek R.

Monash University. Robert.Iansek@med.monash.edu.au

BACKGROUND: Parkinson's disease is a multidimensional disease that results in an 
accumulation of problems over time due to lack of cure, the progressive nature of
the illness and diffuse pathology. This disease debt impacts on movement,
cognition and mood, resulting in disruption of many normal daily activities for
the patients and an increasing burden of care on the spouse and family.
OBJECTIVE: The purpose of this article is to provide the busy general
practitioner with key points in the management of Parkinson's disease which are
of relevance to the patient and the career. DISCUSSION: All health care
professionals who are involved in the management of Parkinson's disease need to
be aware of the expectations of people with this disease and aim to meet these.
Due to the multidimensional nature of this condition these patients are ideally
managed in a team environment incorporating a medical practitioner, a
psychiatrist, nurse, physiotherapist, occupational therapist, speech therapist,
neuropsychologist, social worker and dietician.

PMID: 10561888 [PubMed - indexed for MEDLINE]


26. J Gerontol A Biol Sci Med Sci. 1999 Aug;54(8):M404-9.

Does old age or Parkinson's disease cause bradyphrenia?

Phillips JG, Schiffter T, Nicholls ME, Bradshaw JL, Iansek R, Saling LL.

Department of Psychology, Monash University, Clayton, Vic, Australia.
psy193g@alpha1.cc.monash.edu.au

BACKGROUND: Age-related declines in intellectual functioning have been linked to 
slower processing of information. However, any slowness with advancing age could 
simply reflect slower movement rather than impaired cognition. To assess any
age-related decline in cognitive speed, we used an accuracy-based task that does 
not require a speeded motor response and that measures the time required to
acquire information (inspection time). To identify possible biological mechanisms
of cognitive slowing, this task was also applied to patients with Parkinson's
disease, a basal ganglia disorder that reportedly causes bradyphrenia (slower
thought processes). METHODS: In one experiment, 16 young (mean age 22.4 years)
and 16 older adults (mean age 71.6 years) matched for intelligence and education 
completed an inspection time task. The task required judgments as to order of
onset of two lights, where the interval between onsets ranged from 20-250 msec. A
second experiment compared 16 patients diagnosed with idiopathic Parkinson's
disease and 16 age-matched controls upon the same task. RESULTS: Older adults
demonstrated significant cognitive slowing compared to younger adults. Medicated 
nondemented Parkinsonian patients were not impaired on this task compared to
age-matched controls. CONCLUSIONS: Clinical and empirical impressions of
bradyphrenia in Parkinson's disease may instead reflect advancing age or slower
movement, because the effects of age may be greater in some cases than the
effects of basal ganglia disease once motor dysfunction has been allowed for.

PMID: 10496546 [PubMed - indexed for MEDLINE]


27. Adv Neurol. 1999;80:555-9.

Interdisciplinary rehabilitation in Parkinson's disease.

Iansek R.

Geriatric Research Unit, Kingston Centre, Cheltenham, Melbourne, Australia.

The use of a multidisciplinary team in managing end-stage PD was described,
emphasizing the use of a specifically designed rehabilitation program based on
current concepts of basal ganglia function and malfunction in PD as a means of
unifying the team members, providing them with a common knowledge base and
enabling the team members to speak to the patients with a common language. This
approach has enabled the multidisciplinary team to function in an
interdisciplinary and intradisciplinary manner.

PMID: 10410771 [PubMed - indexed for MEDLINE]


28. J Neurol Neurosurg Psychiatry. 1999 Aug;67(2):199-202.

Regulation of parkinsonian speech volume: the effect of interlocuter distance.

Ho AK, Iansek R, Bradshaw JL.

Neuropsychology Research Unit, Psychology Department, Monash University, Clayton 
3168, Victoria, Australia. Aileen.Ho@sci.monash.edu.au

This study examined the automatic regulation of speech volume over distance in
hypophonic patients with Parkinson's disease and age and sex matched controls.
There were two speech settings; conversation, and the recitation of sequential
material (for example, counting). The perception of interlocuter speech volume by
patients with Parkinson's disease and controls over varying distances was also
examined, and found to be slightly discrepant. For speech production, it was
found that controls significantly increased overall speech volume for
conversation relative to that for sequential material. Patients with Parkinson's 
disease were unable to achieve this overall increase for conversation, and
consistently spoke at a softer volume than controls at all distances (intercept
reduction). However, patients were still able to increase volume for greater
distances in a similar way to controls for conversation and sequential material, 
thus showing a normal pattern of volume regulation (slope similarity). It is
suggested that speech volume regulation is intact in Parkinson's disease, but
rather the gain is reduced. These findings are reminiscent of skeletal motor
control studies in Parkinson's disease, in which the amplitude of movement is
diminished but the relation with another factor is preserved (stride length
increases as cadence-that is, stepping rate, increases).

PMCID: 1736491
PMID: 10406989 [PubMed - indexed for MEDLINE]


29. Arch Phys Med Rehabil. 1999 Jun;80(6):696-701.

Gait consistency over a 7-day interval in people with Parkinson's disease.

Urquhart DM, Morris ME, Iansek R.

Spinal Management Clinics of Victoria, Peninsula Sports Medicine Centre, and
Peninsula Community Health Service, Mornington, Australia.

OBJECTIVE: To evaluate the consistency of temporal and spatial parameters of the 
walking pattern in subjects with idiopathic Parkinson's disease (PD) over a 7-day
interval during the "on" phase of the levodopa medication cycle. SETTING: Walking
patterns were measured on a 12-meter walkway at the Kingston Gait Laboratory,
Cheltenham, using a computerized stride analyzer. SUBJECTS: Sixteen subjects (7
women, 9 men) with PD recruited from the Movement Disorders Clinic at Kingston
Centre. MAIN OUTCOME MEASURES: Speed of walking, stride length, cadence, and the 
percentage of the walking cycle spent in the double limb support phase of gait
were measured, together with the level of disability as indexed by the modified
Webster scale. RESULTS AND CONCLUSIONS: Product-moment correlation coefficients
and intraclass correlation coefficients (ICC 2,1) for repeat measures over a
7-day interval were high for speed (r = .90; ICC = .93), cadence (r = .90; ICC = 
.86), and stride length (r = 1.00; ICC = .97) and moderate for double limb
support duration after removal of outliers (r = .75; ICC = .73); 95% confidence
intervals for the change scores were within clinically acceptable limits for all 
variables. The mean modified Webster score was 11.4 on the first day and 10.1 7
days later. The gait pattern and level of disability in subjects with PD without 
severe motor fluctuations remained stable over a 1-week period when optimal
medication prevailed.

PMID: 10378498 [PubMed - indexed for MEDLINE]


30. Mov Disord. 1999 Jan;14(1):63-8.

Movement-related potentials in Parkinson's disease: external cues and attentional
strategies.

Cunnington R, Iansek R, Bradshaw JL.

Department of Psychology, Monash University, Clayton, Victoria, Australia.

Hypokinetic movement can be greatly improved in Parkinson's disease patients by
the provision of external cues to guide movement. It has recently been reported, 
however, that movement performance in parkinsonian patients can be similarly
improved in the absence of external cues by using attentional strategies, whereby
patients are instructed to consciously attend to particular aspects of the
movement which would normally be controlled automatically. To study the
neurophysiological basis of such improvements in performance associated with the 
use of attentional strategies, movement-related cortical potentials were examined
in Parkinson's disease and control subjects using a reaction time paradigm. One
group of subjects were explicitly instructed to concentrate on internally timed
responses to anticipate the presentation of a predictably timed go signal. Other 
subjects were given no such instruction regarding attentional strategies.
Early-stage premovement activity of movement-related potentials was significantly
increased in amplitude and reaction times were significantly faster for
Parkinson's disease subjects when instructed to direct their attention toward
internally generating responses rather than relying on external cues. It is
therefore suggested that the use of attentional strategies may allow movement to 
be mediated by less automatic and more conscious attentional motor control
processes which may be less impaired by basal ganglia dysfunction, and thereby
improve movement performance in Parkinson's disease.

PMID: 9918346 [PubMed - indexed for MEDLINE]


31. Brain Lang. 1998 Aug;64(1):122-45.

Sequence heterogeneity in Parkinsonian speech.

Ho AK, Bradshaw JL, Cunnington R, Phillips JG, Iansek R.

Psychology Department, Monash University, Clayton, Victoria, 3168, Australia.
aileen.ho@sci.monash.edu.au

Parkinson's disease (PD) is a neurodegenerative movement disorder primarily due
to basal ganglia dysfunction. While much research has been conducted on
Parkinsonian deficits in the traditional arena of musculoskeletal limb movement, 
research in other functional motor tasks is lacking. The present study examined
articulation in PD with increasingly complex sequences of articulatory movement. 
Of interest was whether dysfunction would affect articulation in the same manner 
as in limb-movement impairment. In particular, since very similar (homogeneous)
articulatory sequences (the tongue twister effect) are more difficult for healthy
individuals to achieve than dissimilar (heterogeneous) gestures, while the
reverse may apply for skeletal movements in PD, we asked which factor would
dominate when PD patients articulated various grades of artificial tongue
twisters: the influence of disease or a possible difference between the two motor
systems. Execution was especially impaired when articulation involved a sequence 
of motor program heterogeneous in terms of place of articulation. The results are
suggestive of a hypokinesic tendency in complex sequential articulatory movement 
as in limb movement. It appears that PD patients do show abnormalities in
articulatory movement which are similar to those of the musculoskeletal system.
The present study suggests that an underlying disease effect modulates movement
impairment across different functional motor systems. Copyright 1998 Academic
Press.

PMID: 9675046 [PubMed - indexed for MEDLINE]


32. Motor Control. 1998 Apr;2(2):125-32.

Provision of external cues and movement sequencing in Parkinson's disease.

Rogers MA, Phillips JG, Bradshaw JL, Iansek R, Jones D.

Department of Psychology, Monash University, Wellington Road, Clayton, Victoria
3168, Australia.

The basal ganglia (BG) may play a part in motor sequencing. Individuals with
Parkinson's disease (PD) may exhibit progressive slowing (sequence effect) during
motor sequences such as writing (micrographia) and gait. In the present study, a 
serial two-way choice reaction time (CRT) task was employed, in which advance
information about each next movement was not provided until the participant began
moving, thereby assessing the participant's ability to utilize advance
information. Participants were 13 individuals with idiopathic PD and 13
age-matched controls. Both PD subjects and controls showed a significant sequence
effect in the absence of advance information, possibly reflecting difficulty in
initiating and maintaining movement without external cues. PD subjects and
controls both exhibited a sequence effect at moderate levels of advance
information. At high levels of advance information, PD subjects showed the effect
but controls did not, suggesting that controls, unlike PD subjects, were able to 
use the extra information to facilitate performance, perhaps reflecting more
frontal aspects of impairment in PD.

PMID: 9644283 [PubMed - indexed for MEDLINE]


33. Phys Ther. 1998 Jun;78(6):577-92.

Performance on clinical tests of balance in Parkinson's disease.

Smithson F, Morris ME, Iansek R.

Research Unit, Kingston Centre, Cheltenham, Victoria, Australia.

BACKGROUND AND PURPOSE: Due to the high incidence of falls in people with
idiopathic Parkinson's disease (PD), the assessment of standing balance is a key 
component of physical therapist evaluation. This study investigated performance
on clinical tests of standing balance in subjects with and without PD. SUBJECTS: 
The subjects were 10 persons with PD who had a history of falls (age range =
60-80 years), 10 persons with PD who had no history of falls (age range = 63-79
years), and 10 persons with no known neurological impairment (age range = 60-78
years) who served as a comparison group. METHODS: Subjects were tested on their
ability to maintain stability in 3 conditions: (1) steady standing (feet apart,
feet together, tandem stance, step stance, and single-limb stance), (2) in
response to perturbations generated by self-initiated movements (arm raise,
functional reach, bend-reach, and step tests), and (3) in response to an external
perturbation to upright stance (shoulder tug). Balance was measured at peak
dosage in the levodopa medication cycle (in the morning) and 7 days later.
RESULTS: The mean Hoehn and Yahr Disability Scale score was 3.0 for the fallers
with PD and 2.5 for the nonfallers with PD. Performance on the tandem stance,
single-limb stance, functional reach, and shoulder tug tests demonstrated
differences between the subjects with PD and the comparison group and between the
fallers and nonfallers with PD. The results of these tests were highly repeatable
over 7 days (ICC = .61-.94). CONCLUSION AND DISCUSSION: Although there was a
small sample size, performance was highly consistent across 7 days when testing
occurred during peak dosage of levodopa. A small battery of tests were sensitive 
enough to discriminate between people with PD who fall and those with no history 
of falls.

PMID: 9626270 [PubMed - indexed for MEDLINE]


34. Brain. 1998 Apr;121 ( Pt 4):743-53.

Bimanual co-ordination in Parkinson's disease.

Johnson KA, Cunnington R, Bradshaw JL, Phillips JG, Iansek R, Rogers MA.

Department of Psychology, Monash University, Clayton, Victoria, Australia.

The basal ganglia may be involved in bimanual co-ordination. Parkinson's disease 
(which impairs basal ganglia output) is clinically reported to cause difficulties
in the performance of co-ordinated bimanual movements. Nevertheless, any bimanual
co-ordination difficulties may be task specific, as experimental observations are
equivocal. To infer the role of the basal ganglia in co-ordinating the two arms, 
this study investigated the bimanual co-ordination of patients with Parkinson's
disease. Sixteen Parkinson's disease patients and matched control subjects
performed a bimanual cranking task, at different speeds (1 and 2 Hz) and phase
relationships. All subjects performed the required bimanual in-phase movement on 
a pair of cranks, at fast (2 Hz) and slow (1 Hz) speeds. However, the Parkinson's
disease patients were unable to perform the asymmetrical anti-phase movement, in 
which rotation of the cranks differed by 180 degrees, at either speed; but
instead reverted to the in-phase symmetrical movement. For Parkinson's disease
patients, performance of the in-phase movement was more accurate and stable when 
an external timing cue was used; however, for anti-phase movement, the external
cue accentuated the tendency for patients to revert to more symmetrical, in-phase
movements.

PMID: 9577398 [PubMed - indexed for MEDLINE]


35. Mov Disord. 1998 Jan;13(1):61-9.

Abnormalities in the stride length-cadence relation in parkinsonian gait.

Morris M, Iansek R, Matyas T, Summers J.

Kingston Centre, Cheltenham, Australia.

The purpose of this investigation was to clarify abnormalities in the stride
length-cadence relation in gait hypokinesia in Parkinson's disease (PD). A second
aim was to investigate the effect of levodopa medication on the foot-step
pattern. In the first experiment, 20 subjects with idiopathic PD and 20 age-,
sex-, and height-matched controls performed a series of 10 m walking trials at
cadence rates ranging from 40 steps/min to 180 steps/min. Cadence rates were set 
by an electronic metronome, and gait patterns were measured by using a footswitch
stride-analyzer system. By instructing subjects to concentrate on walking in time
to the metronome beat, the baseline stride length could be monitored for a range 
of velocities with the compensatory effects of cadence removed. Linear-regression
analysis revealed that the mean slope for the regression of stride length against
cadence was not different from normal in PD, although there was a statistically
significant difference in mean intercept between the PD group (0.25) and the
control group (0.59); [t (19) = -4.76; p = 0.0001]. The second experiment
evaluated the effects of levodopa on stride-length regulation in 10 subjects with
idiopathic PD on average 45 min before and after the first morning dose was
administered. There was a statistically significant increase in stride length for
all cadence rates from premedication to postmedication phases and the maximal
stride length was achieved at higher cadence rates after medication. The slope of
the regression of stride length against cadence did not alter according to
medication status, although the mean intercept was significantly lower before
levodopa (-0.06) compared with after levodopa (0.27); [t (9) = -3.83; p = 0.004].
These results suggest that defective scaling of stride length underlies gait
disturbance in PD.

PMID: 9452328 [PubMed - indexed for MEDLINE]


36. J Neurol Neurosurg Psychiatry. 1997 Oct;63(4):556-7.

Rehabilitation of gait in Parkinson's disease.

Iansek RT, Morris M.

Comment on:
    J Neurol Neurosurg Psychiatry. 1997 Jan;62(1):22-6.

PMCID: 2169774
PMID: 9343155 [PubMed - indexed for MEDLINE]


37. Brain. 1997 Aug;120 ( Pt 8):1339-53.

Movement-related potentials in Parkinson's disease. Motor imagery and movement
preparation.

Cunnington R, Iansek R, Johnson KA, Bradshaw JL.

Department of Psychology, Monash University, Clayton, Victoria, Australia.

Movement-related potentials (MRPs) associated with voluntary movements reflect
cortical activity associated with processes of movement preparation and movement 
execution. Early-stage pre-movement activity is reduced in amplitude in
Parkinson's disease. However, it is unclear whether this neurophysiological
deficit relates to preparatory or execution-related activity, since previous
studies have not been able to separate different functional components of MRPs.
Motor imagery is thought to involve mainly processes of movement preparation,
with reduced involvement of end-stage movement execution-related processes.
Therefore, MRP components relating to movement preparation and execution may be
examined separately by comparing MRPs associated with imagined and actual
movements. In this study, MRPs were recorded from 14 subjects with Parkinson's
disease and 10 age-matched control subjects while they performed a sequential
button-pressing task, and while they imagined performance of the same task.
Early-stage pre-movement activity was present in both Parkinson's disease
patients and control subjects when they imagined movement, but was reduced in
amplitude compared with that for actual movement. Movement execution-related
components, arising predominantly from the primary motor cortex, were relatively 
unaffected in Parkinson's disease subjects. However, motor preparatory processes,
probably involving the supplementary motor area, were reduced in amplitude
overall and abnormally prolonged, indicating impaired termination following the
motor response. Further, this impaired termination of preparatory-phase activity 
was observed only in patients with more severe parkinsonian symptoms, and not in 
early-stage Parkinson's disease.

PMID: 9278627 [PubMed - indexed for MEDLINE]


38. Phys Ther. 1996 Jul;76(7):763-77; discussion 778-80.

Temporal stability of gait in Parkinson's disease.

Morris ME, Matyas TA, Iansek R, Summers JJ.

Geriatric Research Unit, Kingston Center, Cheltenham, Victoria, Australia.

BACKGROUND AND PURPOSE. Evaluation of physical therapy for gait disorders in
patients with Parkinson's disease (PD) requires an under-standing of how the
patients' medication cycle affects function. Four experiments were conducted to
investigate stability of gait variables. METHODS AND RESULTS. In experiment 1, 15
subjects with idiopathic PD and 15 subjects without PD performed two sets of gait
trials spaced 30 minutes apart, with the initial trial conducted with the
subjects at a peak dose of medication. Strong correlations, as determined by
intraclass correlation coefficients (ICC[2,1]), occurred between repeat measures 
of speed (ICC = .92), cadence (ICC = .92), stride length (ICC = .94), and time
spent in double support (DS) (ICC = .93). In experiment 2, 16 subjects with PD
were tested at the same time on two consecutive days. There was good
repeatability for speed (ICC = .88), cadence (ICC = .85), stride length (ICC =
.84), and DS (ICC = .80). When we assessed the repeatability of measurements
taken at peak dose and at end of dose, there were low correlations for speed (ICC
= -.54), cadence (ICC = -.07), stride length (ICC = -.35), and DS (ICC = -.38).
In a final experiment on 16 subjects with PD, we used time-series analysis to
examine the stability of measurements taken every 15 minutes for 2 1/2 hours.
Slopes of regression models, standard deviations, and residual autocorrelations
were negligible, indicating that the measurements were stable. CONCLUSION AND
DISCUSSION. The parkinsonian gait pattern is reproducible across either brief
time intervals or 24 hours when peak medication prevails. At the end of dose,
however, marked changes in gait occur, apparently related to depletion of
medication.

PMID: 8677280 [PubMed - indexed for MEDLINE]


39. Brain. 1996 Jun;119 ( Pt 3):815-22.

Effects of magnetic stimulation over supplementary motor area on movement in
Parkinson's disease.

Cunnington R, Iansek R, Thickbroom GW, Laing BA, Mastaglia FL, Bradshaw JL,
Phillips JG.

Geriatric Research Unit, Kingston Centre, Cheltenham, Victoria, Australia.

Movement execution can be delayed by transcranial magnetic stimulation delivered 
over primary motor cortical areas, resulting in transient inhibition of
cortico-motor output. Inhibition or disruption of higher-order motor planning and
preparatory processes, such as are thought to occur in the supplementary motor
area (SMA), would allow an examination of processes at other stages of the motor 
control system. In this study, six subjects with Parkinson's disease and six
healthy control subjects performed a non-cued sequential finger movement task. At
various times relative to movement, high-intensity single-pulse magnetic
stimulation was delivered over the region of the SMA, with minimal current spread
to primary motor areas. When magnetic stimulation was given at early stages
during the movement for parkinsonian subjects, movement times were significantly 
increased, indicating disrupted movements. Supplementary motor area stimulation
had no effect when delivered during later stages of the movement or immediately
prior to movement onset, and had no apparent effect on control subjects at any
time. It is therefore suggested that the SMA is important in motor planning and
preparatory processes, since SMA stimulation has no effect on movements in their 
later stages when planning may be complete, but may disrupt movements in their
early stages, when preparation for later stages may still be in progress.
Further, possible instability of motor planning/preparation processes in
Parkinson's disease is suggested, since these processes appeared more susceptible
to disruption by magnetic stimulation in parkinsonian subjects than controls.

PMID: 8673493 [PubMed - indexed for MEDLINE]


40. Brain. 1996 Apr;119 ( Pt 2):551-68.

Stride length regulation in Parkinson's disease. Normalization strategies and
underlying mechanisms.

Morris ME, Iansek R, Matyas TA, Summers JJ.

Geriatric Research Unit, Kingston Centre, Cheltenham, Australia.

Results of our previous studies have shown that the slow, shuffling gait of
Parkinson's disease patients is due to an inability to generate appropriate
stride length and that cadence control is intact and is used as a compensatory
mechanism. The reason for the reduced stride length is unclear, although
deficient internal cue production or inadequate contribution to cortical motor
set by the basal ganglia are two possible explanations. In this study we have
examined the latter possibility by comparing the long-lasting effects of visual
cues in improving stride length with that of attentional strategies. Computerized
stride analysis was used to measure the spatial (distance) and temporal (timing) 
parameters of the walking pattern in a total of 54 subjects in three separate
studies. In each study Parkinson's disease subjects were trained for 20 min by
repeated 10 m walks set at control stride length (determined from control
subjects matched for age, sex and height), using either visual floor markers or a
mental picture of the appropriate stride size. Following training, the gait
patterns were monitored (i) every 15 min for 2 h; (ii) whilst interspersing
secondary tasks of increasing levels of complexity; (iii) covertly, when subjects
were unaware that measurement was taking place. The results demonstrated that
training with both visual cues and attentional strategies could maintain normal
gait for the maximum recording time of 2 h. Secondary tasks reduced stride length
towards baseline values as did covert monitoring. The findings confirm that the
ability to generate a normal stepping pattern is not lost in Parkinson's disease 
and that gait hypokinesia reflects a difficulty in activating the motor control
system. Normal stride length can be elicited in Parkinson's disease using
attentional strategies and visual cues. Both strategies appear to share the same 
mechanism of focusing attention on the stride length. The effect of attention
appears to require constant vigilance to prevent reverting to more automatic
control mechanisms.

PMID: 8800948 [PubMed - indexed for MEDLINE]


41. J Clin Exp Neuropsychol. 1996 Apr;18(2):276-90.

Simon effect and attention in Parkinson's disease: a comparison with Huntington's
disease and Tourette's syndrome.

Cope MT, Georgiou N, Bradshaw JL, Iansek R, Phillips JG.

Monash University, Clayton, Victoria, Australia.

Patients with hyperkinetic basal-ganglia disorders (Huntington's disease, HD; and
Tourette's syndrome, TS) have difficulty with spatially incongruent
stimulus-response configurations, the Simon effect, and with inhibiting
inappropriate responses in a conditionality paradigm. However Parkinson's disease
(PD) patients with hypokinetic basal-ganglia disorder show normal (for their age)
conditionality and congruency effects, probably because the task is extremely
sensitive to aging and PD patients are typically older than HD and TS
individuals. Overall, HD patients were by far the most affected, reflecting the
likely greater involvement of the caudate (with its predominantly cognitive role)
than the putamen; the latter structure, with a predominantly motor involvement,
is the more affected in PD.

PMID: 8780962 [PubMed - indexed for MEDLINE]


42. Brain. 1995 Dec;118 ( Pt 6):1613-7.

Review article: the functions of the basal ganglia and the paradox of stereotaxic
surgery in Parkinson's disease.

Iansek R, Bradshaw J, Phillips J, Morris ME, Cunnington R.

Comment on:
    Brain. 1994 Aug;117 ( Pt 4):877-97.

PMID: 8595490 [PubMed - indexed for MEDLINE]


43. Neuropsychologia. 1995 Oct;33(10):1193-203.

Contingent and non-contingent auditory cueing in Parkinson's disease.

Kritikos A, Leahy C, Bradshaw JL, Iansek R, Phillips JG, Bradshaw JA.

Geriatric Research Unit, Kingston Centre, Cheltenham, Victoria, Australia.

Parkinson's disease (PD) patients and their normal controls performed two
experiments involving a sequential movement task, depressing a series of buttons 
at choice points along a response board. Visual or auditory cues were presented
prior to each move according to various contingencies. PD, a disorder
characterised by degeneration of the basal ganglia (BG), typically manifests with
poor execution of motor sequences. We found that external cueing facilitated
motor sequencing in PD patients. In particular, auditory cues which occurred late
in the movement cycle maximally facilitated switching between subcomponents of a 
sequence. Based on physiological findings reported in the primate literature
[Brotchie et al., Brain 114, 1685-1702, 1978; Schultz and Romo, Exp. Brain Res.
1, 363-384, 1992], it is suggested that external cues enhance performance by
replacing defective, internally generated cues (discharges) of the BG. This has
implications for the use of physical training strategies in the treatment of PD.

PMID: 8552224 [PubMed - indexed for MEDLINE]


44. Brain. 1995 Aug;118 ( Pt 4):935-50.

Movement-related potentials in Parkinson's disease. Presence and predictability
of temporal and spatial cues.

Cunnington R, Iansek R, Bradshaw JL, Phillips JG.

Department of Psychology, Monash University, Clayton, Victoria, Australia.

Activity of the supplementary motor area may be inferred from movement-related
potentials (MRPs) which are associated with the preparation and execution of
voluntary, or internally determined movements. Supplementary motor area activity 
may be abnormal in Parkinson's disease since its major input from the basal
ganglia is disrupted. Investigation of the abnormalities in supplementary motor
area activity associated with movement deficits in Parkinson's disease may
therefore reveal functions of the basal ganglia and the supplementary motor area.
Movement-related potentials associated with sequential movements were
investigated under various cueing conditions in Parkinson's disease subjects and 
age-matched controls. In controls, MRPs revealed involvement of the supplementary
motor area in movements which can be internally determined (non-cued and
externally cued, predictable movements, but not unpredictable movements). In
Parkinson's disease, however, the supplementary motor area was only involved in
movements which must be internally determined (non-cued movements, but not
externally cued movements); therefore impaired internal control mechanisms,
operating via the supplementary motor area, are bypassed when external cues are
given. As a result, Parkinson's disease patients are more reliant on external
cues and are unable to use predictive models to internally guide movement.
Supplementary motor area involvement also relied on the predictability (in
controls) or presence (in Parkinson's disease) of timing cues and not spatial
cues, indicating a role of the supplementary motor area and basal ganglia in the 
temporal organizations of sequential movement rather than the programming of
specific movements. For non-cued movements, abnormalities in MRPs for Parkinson's
disease subjects consisted of delayed MRP onset and peak times, and prolonged
cortical activity following movement. These observations led to a proposed model 
of the interaction between the basal ganglia and the supplementary motor area,
involving the temporal organization of voluntary and internally determined
sequential movements.

PMID: 7655889 [PubMed - indexed for MEDLINE]


45. J Neurol Neurosurg Psychiatry. 1994 Dec;57(12):1532-4.

Ability to modulate walking cadence remains intact in Parkinson's disease.

Morris ME, Iansek R, Matyas TA, Summers JJ.

Geriatric Neurology Research Unit, Kingston Centre, Australia.

Gait hypokinesia (slowness) is a characteristic feature of Parkinson's disease.
It is not clear, however, whether the slowness is due to a problem in regulation 
of the timing of consecutive steps or the control of stride size. Examination of 
cadence control for slow to medium walking speeds has shown an increase in step
frequency that was a compensation for reduced stride length. In this
investigation the ability of Parkinsonian patients to modulate their cadence
(steps per minute) at the fast walking speeds exhibited by age and height matched
controls was examined. The findings indicated that cadence control remains
unaffected throughout its entire range in Parkinson's disease and that gait
hypokinesia is directly attributable to an inability to internally generate
sufficiently large steps.

PMCID: 1073238
PMID: 7798986 [PubMed - indexed for MEDLINE]


46. Neuropsychologia. 1994 Nov;32(11):1383-96.

Parkinsonian patients without dementia or depression do not suffer from
bradyphrenia as indexed by performance in mental rotation tasks with and without 
advance information.

Duncombe ME, Bradshaw JL, Iansek R, Phillips JG.

Department of Psychology, Monash University, Clayton, Victoria, Australia.

A predominant symptom of Parkinson's disease is akinesia and bradykinesia,
slowing in the initiation and execution of voluntary movement. There has long
been speculation as to whether cognitive processes undergo similar processes, but
findings may be confounded by the frequent co-occurrence of dementia and/or
depression. Mental rotation provides an internal or cognitive analogue of real
movement, and enables us to determine the speed of such mental processes
independent of any concurrent motor slowing in response initiation and execution.
Medicated patients with Parkinson's disease who were free of dementia and
depression were found to be able to mentally rotate alphanumeric or figural
stimuli, with and without advance information as to the view (front or back) of a
stick figure shortly to be shown, as rapidly as normal healthy controls. We
conclude that cognitive processes involved in mental rotation are not necessarily
slowed in Parkinson's disease.

PMID: 7877746 [PubMed - indexed for MEDLINE]


47. Brain. 1994 Oct;117 ( Pt 5):1169-81.

The pathogenesis of gait hypokinesia in Parkinson's disease.

Morris ME, Iansek R, Matyas TA, Summers JJ.

Department of Behavioural Health Sciences, La Trobe University, Bundoora,
Australia.

To identify the fundamental deficit in gait hypokinesia in Parkinson's disease
(PD) we conducted a series of experiments that compared PD subjects with age- and
height-matched controls in their capacity to regulate either stride length,
cadence (steps per minute) or both parameters to three conditions. In the first
condition the spatial and temporal parameters of gait were documented for slow,
normal and fast walking. The second condition compared parkinsonian gait with the
walking pattern of elderly controls whilst controlling for two movement speeds:
fast (control preferred) speed and slow (PD preferred) speed. In the third
condition we examined the ability of PD subjects to regulate one parameter (e.g. 
stride length) when the other two parameters (e.g. velocity and cadence) were
held at control values. A total of 34 PD subjects and 34 matched controls were
tested using a footswitch stride analysis system that measured the spatial and
temporal parameters of gait for a series of 10 m walking trials. Parkinsonian
subjects exhibited marked gait hypokinesia in each of the experiments. Although
they retained the capacity to vary their gait velocity in a similar manner to
controls, their range of response was reduced. Within the lower velocity range,
PD subjects could vary their speed of walking by adjusting cadence and, to a
lesser extent, stride length. However, when the speed of walking was controlled, 
the stride length was found to be shorter and the cadence higher in PD subjects
than in controls. Stride length could not be upgraded by internal control
mechanisms in response to a fixed cadence set for age and height-matched
velocity. In contrast, cadence was readily modulated by external cues and by
internal control mechanisms when stride length was fixed to the values obtained
for age- and height-matched controls. It was concluded that regulation of stride 
length is the fundamental problem in gait hypokinesia and the relative increase
in cadence exhibited by PD subjects is a compensatory mechanism for the
difficulty in regulating stride length. These findings are discussed in the
context of the hypothesized role of the basal ganglia in generating internal cues
for the maintenance of the gait sequence and in relation to the structuring of
movement rehabilitation strategies.

PMID: 7953597 [PubMed - indexed for MEDLINE]


48. J Neurol. 1994 Jun;241(7):439-47.

Could bradykinesia in Parkinson's disease simply be compensation?

Phillips JG, Martin KE, Bradshaw JL, Iansek R.

Psychology Department, Monash University, Clayton, Victoria, Australia.

Even normal movements can be slow and hesitant. To distinguish between
bradykinesia and the simple slow inefficiency sometimes seen in normal movement, 
we matched the movement durations of 12 patients with Parkinson's disease (PD)
and 12 age-matched controls and examined end-point accuracy, number of
submovements, force inefficiency, and relative duration of acceleration and
deceleration phases of movement. Subjects used an electronic pen which sampled
pen-tip position at 200 Hz, and performed a sequence of drawing movements to nine
targets (0.5, 1, or 2 cm diameter) upon a WACOM SD420 graphics tablet. Patients
could be trained to move at the preferred speed of controls (and vice versa).
When moving at the same fast speed as controls, patient's movements were less
accurate (increased end-point spread). Even when moving at their own preferred
speed, patients' movements were less efficient (more submovements, more zero
crossings in acceleration function) than controls moving at the same speed. If
bradykinesia simply reflected increased caution and visual guidance, we would
expect patients to exhibit prolonged decelerative phases of movement associated
with terminal guidance. However, patients consistently required prolonged
accelerative phases of movement, suggesting that there was a problem in
generating appropriate movement forces to produce the required end-point
accuracy. It is hypothesised that bradykinesia is not simply a compensation for
defective preparatory processes, but may reflect a defective internal cue in PD
which disrupts and impairs the outflow of motor responses.

PMID: 7931446 [PubMed - indexed for MEDLINE]


49. J Neurol Neurosurg Psychiatry. 1994 Mar;57(3):368-70.

Reduction in external cues and movement sequencing in Parkinson's disease.

Georgiou N, Bradshaw JL, Iansek R, Phillips JG, Mattingley JB, Bradshaw JA.

Monash University, Clayton, Victoria, Australia.

To identify the focus of impairment in the performance of sequential movements of
patients with Parkinson's disease, the extent of their reliance on external cues 
was examined. Eighteen patients with idiopathic Parkinson's disease and their
matched controls performed a series of button presses at sequential choice points
along a response board. The illuminated pathway to be followed successively
extinguished ahead of each move according to three levels of reduction of
external cues. Patients with Parkinson's disease were particularly disadvantaged 
with high levels of reduction of external cueing in terms both of movement
preparation time (button down time) and movement execution time (movement time
between buttons). Moreover, with high levels of reduction of external cueing,
patients with Parkinson's disease were particularly subject to progressive
slowing (movement time, not down time) further down the sequence. The basal
ganglia may help generate internal cues for releasing successive stages of a
predefined movement sequence.

PMCID: 1072831
PMID: 8158189 [PubMed - indexed for MEDLINE]


50. J Clin Exp Neuropsychol. 1994 Feb;16(1):117-28.

Allocation of attention to programming of movement sequences in Parkinson's
disease.

Jones DL, Bradshaw JL, Phillips JG, Iansek R, Mattingley JB, Bradshaw JA.

Monash University, Melbourne, Australia.

The allocation of attention to the programming and execution of movement
sequences was examined in Parkinson's disease (PD). The time taken to initiate
and execute sequences of one, three, and five button taps was examined, while
also varying the hand used (left or right) and the attentional resources that
could be allocated to sequencing (using single- versus dual-task conditions).
These results showed that performance anomalies in PD were most apparent with the
preferred right hand under single-rather than dual-task conditions. Subjects
suffering from PD may tend to divert attention from the right hand under
single-task conditions, and perhaps with short sequences, as well as being less
likely to prepare sequences of more than three movements in advance with that
hand. These effects were unlikely to reflect asymmetric pathology. If the right
hand of such subjects has in some respects now come to behave more like a
"clumsy" left hand, this may reflect a deliberate strategic choice in an attempt 
to cope with a movement impairment.

PMID: 8150882 [PubMed - indexed for MEDLINE]


51. Exp Brain Res. 1994;102(1):131-40.

Inaccuracy and instability of sequential movements in Parkinson's disease.

Martin KE, Phillips JG, Iansek R, Bradshaw JL.

Psychology Department, Monash University, Clayton Vic, Australia.

Animal studies suggest that the basal ganglia (BG) provide internal cues to
trigger submovements in a movement sequence, with Parkinson's disease (PD)
involving a deficiency in this cueing mechanism. However, it is not clear why
defective internal cues can produce slow movements, or the extent to which slow
movements are indeed the basic movement abnormality or are perhaps a compensatory
mechanism for some other primary deficit. In this study we examined a number of
the kinematic indices of matched fast movements between PD patients and
age-matched controls, performed with and without reductions in visual cues for
guidance, in order to delineate the relationship between the internal cue and the
kinematic characteristics of these movements. Fourteen patients with PD, and
their matched controls, used an electronic pen, which sampled pen-tip position at
200 Hz, and performed a sequence of drawing movements to nine targets upon a
WACOM SD 420 graphics tablet. Subjects were trained to perform the movement
sequence at a fast speed and were then required to perform the same movement at
the same speed with reduced visual cues. Kinematic analysis indicated that, when 
visual cues were reduced, movements of PD patients became spatially and
temporally unstable as they were progressively performed down the sequence. The
instability was associated with an abnormal force profile increase in peak
movement velocity and target overshoot, which became additive as the submovements
progressed. We suggest that defective cue production is the basic deficit in
parkinsonian hypokinesia. The defective cue leads to problems synchronising
preparatory activity, which then results in abnormalities in movement forces
which are characterised by unpredictable and inaccurate movement endpoints. When 
movements are strung together in a sequence the inaccuracy is additive leading to
motor instability.

PMID: 7895789 [PubMed - indexed for MEDLINE]


52. Brain. 1993 Dec;116 ( Pt 6):1575-87.

An evaluation of the role of internal cues in the pathogenesis of parkinsonian
hypokinesia.

Georgiou N, Iansek R, Bradshaw JL, Phillips JG, Mattingley JB, Bradshaw JA.

Department of Psychology, Monash University, Clayton, Australia.

Our animal studies suggest that the basal ganglia provide an internal
non-specific cue to trigger movement and imply that Parkinson's disease involves 
a deficiency in this cueing mechanism. Indeed parkinsonian patients typically
rely upon external visual cues. To assess the effects of such non-specific cueing
mechanisms on movement, we examined patients' utilization of a variety of
auditory cues. Ten patients suffering from Parkinson's disease, and their matched
controls, pressed buttons at a series of two-way choice points sequentially down 
a pathway, both when the latter remained illuminated throughout its length, and
when it had to be followed from memory alone. In other experimental conditions,
auditory cues were also provided, either contingent upon the previous response,
at its initiation (a medium level of advance information) or at its completion (a
low level of advance information), or as a series of regularly paced
(non-contingent) auditory cues (from a metronome). In addition to error data, we 
recorded down time (DT, time to initiate each next response) and movement time
(MT, time to execute each next response). However, both DT and MT measurements
showed that parkinsonian patients were enormously disadvantaged by the absence of
external cues. While contingent auditory cues were of some help, the performance 
of patients with Parkinson's disease was dramatically improved by the provision
of non-contingent auditory information. Moreover, parkinsonian patients, unlike
controls, were greatly affected by the length of individual sub-movements,
especially in the absence of external cues. When the pathway to be followed
remained illuminated, sub-movement length had little effect. We conclude that for
well-learnt, predictable sequences the basal ganglia provide a non-specific
internal cue that is necessary for switching between one movement and the next in
a movement sequence, and also for development of preparatory activity for each
sub-movement in the sequence.

PMID: 8293289 [PubMed - indexed for MEDLINE]


53. J Neurol Neurosurg Psychiatry. 1993 Apr;56(4):419-22.

Coding of movement direction and amplitude in Parkinson's disease: are they
differentially impaired (or unimportant)?

Jones DL, Phillips JG, Bradshaw JL, Iansek R, Bradshaw JA.

Department of Psychology, Monash University, Melbourne, Australia.

A recent study suggested that the preparation of movement direction, but not
amplitude, may be selectively impaired by Parkinson's disease (PD). The authors
examined the reprogramming of direction only, amplitude only, and direction and
amplitude together, and included a control condition in which neither parameter
was reprogrammed. The findings suggested that neither direction nor amplitude
coding was differentially impaired in PD. Thus the structures affected by PD may 
not be uniquely involved in specifying only the direction or the amplitude of
future movements; these structures probably have more complex higher-level roles.

PMCID: 1014962
PMID: 8482965 [PubMed - indexed for MEDLINE]


54. Neuropsychologia. 1993 Jan;31(1):51-66.

Re-orientation of attention in Parkinson's disease: an extension to the
vibrotactile modality.

Bradshaw JL, Waterfall ML, Phillips JG, Iansek R, Mattingley JB, Bradshaw JA.

Department of Psychology, Monash University, Clayton, Victoria, Australia.

Parkinson's disease (PD), a disorder of the dopaminergic nigro-striatal pathway, 
is associated with both motor and cognitive impairments, including perhaps the
ability to focus attention. Disturbances of attentional processes were further
examined in a series of vibrotactile choice reaction time (cRT) experiments
involving biased probabilities of event occurrence, or valid/invalid precueing.
Results of three experiments suggest that PD subjects, compared to controls, are 
less adept at maintaining attention in space. The performance of the PD subjects 
improved, however, when they were permitted to direct their gaze to one hand or
the other, and when valid external precues were provided before each trial.
Observed similarities between the cognitive and motor deficits of PD subjects
support the notion that there is a close coupling between the mechanisms
coordinating attention and movement.

PMID: 8437682 [PubMed - indexed for MEDLINE]


55. J Clin Exp Neuropsychol. 1992 Sep;14(5):762-72.

Programming of single movements in Parkinson's disease: comparison with
Huntington's disease.

Jones DL, Phillips JG, Bradshaw JL, Iansek R, Bradshaw JA.

Monash University, Melbourne, Australia.

The preparation of individual finger movements was examined in Parkinson's
disease (PD), in comparison with a similar study of Huntington's disease (HD).
Motor programming was varied by increasing the amount of information available in
advance of each movement. PD patients had particular difficulty when there was no
cue light in advance of the movement, and when two upcoming movements were cued
ahead of the current movement. Such difficulties suggest that PD patients may
have difficulty in performing movements without sensory cuing, and in maintaining
and organising a future sequence of movements. HD patients had been previously
shown to have similar deficits. Commonalities in these once contrasted disorders 
probably arise from disruption of common mechanisms.

PMID: 1474144 [PubMed - indexed for MEDLINE]


56. J Neurol Neurosurg Psychiatry. 1992 Jun;55(6):503-6.

Impairment in bilateral alternating movements in Parkinson's disease?

Jones DL, Phillips JG, Bradshaw JL, Iansek R, Bradshaw JA.

Department of Psychology, Monash University, Clayton, Victoria, Australia.

Although problems in bilateral simultaneous movements in Parkinson's disease (PD)
are well known, such deficits have not been reported to be any more impaired than
simultaneous movements within the same limb. This is surprising, since (a) the
parallels between supplementary motor area (SMA) damage and PD are well
documented and (b) the SMA seems to play a special role in bilateral motor
control. Bilateral versus unilateral movements in PD were examined by using a
task that compared alternating movements of fingers of the same hand with
alternating movements of fingers of the opposite hands. PD patients showed
particular problems in programming and transferring motor activity to fingers on 
the opposite side of the body, as opposed to switching motor activity between
fingers on the same side of the body. These findings outline the relevance of SMA
dysfunction to PD.

PMCID: 1014910
PMID: 1619421 [PubMed - indexed for MEDLINE]


57. Aust N Z J Med. 1991 Jun;21(3):314-8.

Intermittent subcutaneous apomorphine injection treatment for parkinsonian motor 
oscillations.

Kempster PA, Iansek R, Larmour I.

Monash Medical Centre, Melbourne, Vic., Australia.

Eight patients with severe Parkinsonian motor oscillations have been treated with
the dopamine receptor agonist apomorphine by intermittent subcutaneous
self-injection as an adjunct to oral anti-Parkinsonian medication. The dopamine
receptor antagonist domperidone was also given by mouth to prevent nausea. Six
patients remain on chronic treatment (mean period 6.5 months) with improved
control of motor function in each case. Four have had major enhancement of their 
quality of life. Benefits of this treatment stem from the training of patients to
use intelligent behaviour to administer a promptly acting and effective
pharmacological agent, thereby exercising a degree of direct control over
previously unpredictable variations in motor performance.

PMID: 1953509 [PubMed - indexed for MEDLINE]

TITLE: Physiological localisation in functional neurosurgery for movement disorders: a simple approach.
AUTHORS: Iansek R; Rosenfeld JV; Feniger H; Huxham F
AUTHOR AFFILIATION: Geriatric Neurology Service, Kingston Centre, Melbourne, Australia.
SOURCE: J Clin Neurosci 2000 Jan;7(1):29-33
CITATION IDS: PMID: 10847647 UI: 20304297
ABSTRACT: Controversy exists between anatomical methods and single cell recording as the preferred approach in target localisation in functional neurosurgery for movement disorders. The controversy centres on accuracy as compared to practicality. We describe a mapping technique of semi-microstimulation utilising threshold measurements which has been used in 66 procedures in 50 subjects. We compared the accuracy of anatomical localisation with the final chosen target using the above technique. We also compared the benefit, the side effects and the surgical complication rate with published data on single cell recording and anatomical localisation. The mean difference in 3-dimensional space between the anatomical target and the physiological target was 6.85 mm (P < 0.0001). A good response was obtained in 80% of procedures. Mortality was 1.5%. The surgical complication rate was 1.5%. Mild side effects, serious side effects, transient side effects and permanent side effects were evident in 4.5%, 10.6%, 6.1% and 9.1% of procedures. These figures compared better than anatomical studies and similar to single cell recording studies. It is concluded that this approach provides both accuracy and simplicity and is recommended as a compromise to the currently available methods.

2000/07
2000/15 11:00


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TITLE: Speech volume regulation in Parkinson's disease: effects of implicit cues and explicit instructions.
AUTHORS: Ho AK; Bradshaw JL; Iansek R; Alfredson R
AUTHOR AFFILIATION: Psychology Department, Monash University, Clayton, Victoria, Australia. aileen.ho@sci.monash.edu.au
SOURCE: Neuropsychologia 1999 Dec;37(13):1453-60
CITATION IDS: PMID: 10617265 UI: 20083555
ABSTRACT: This study examined the regulation of speech volume in hypophonic subjects with Parkinson's disease (PD) and age- and gender-matched controls. The first two experiments investigated the ability of subjects with PD to automatically regulate speech volume in response to two types of implicit cue: (i) background noise (BGN) and (ii) instantaneous auditory feedback (IAF). Control subjects demonstrated the Lombard effect by automatically speaking louder when competing against increasing levels of background noise. They also showed the reverse effect, decreasing speech volume when increasing levels of facilitative instantaneous auditory feedback were provided. Subjects with PD demonstrated decreased overall speech volume; they were less able than controls to appropriately increase volume as background noise increased, and to decrease volume as IAF increased. Thus, subjects with PD demonstrated over-constancy of speech volume and failed to respond to the implicit cues integral to volumetric scaling. A further experiment (3) was carried out to contrast the regulation of volume in response to implicit cue with an explicit attention-driven cue (i.e. instructions regarding volume level). As in Experiments 1 and 2, subjects with PD exhibited reduced speech volume. Under explicit volume instructions, the ability of subjects with PD to regulate volume was normalised. These findings suggest that subjects with PD have the capacity to speak with normal volume provided they consciously attend to speaking loudly. In subjects with PD, overall speech volume was always lower than for control subjects, suggesting a reduction of cortical motor set in the articulatory system similar to that demonstrated by the reduced amplitude of limb movements (hypokinesia) in the motor system.

2000/01
2000/05 09:00


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TITLE: Key points in the management of Parkinson's disease.
AUTHORS: Iansek R
AUTHOR AFFILIATION: Monash University. Robert.Iansek@med.monash.edu.au
SOURCE: Aust Fam Physician 1999 Sep;28(9):897-901
CITATION IDS: PMID: 10561888 UI: 20024531
ABSTRACT: BACKGROUND: Parkinson's disease is a multidimensional disease that results in an accumulation of problems over time due to lack of cure, the progressive nature of the illness and diffuse pathology. This disease debt impacts on movement, cognition and mood, resulting in disruption of many normal daily activities for the patients and an increasing burden of care on the spouse and family.

OBJECTIVE: The purpose of this article is to provide the busy general practitioner with key points in the management of Parkinson's disease which are of relevance to the patient and the career.

DISCUSSION: All health care professionals who are involved in the management of Parkinson's disease need to be aware of the expectations of people with this disease and aim to meet these. Due to the multidimensional nature of this condition these patients are ideally managed in a team environment incorporating a medical practitioner, a psychiatrist, nurse, physiotherapist, occupational therapist, speech therapist, neuropsychologist, social worker and dietician.

1999/11
1999/24 09:00

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TITLE: Does old age or Parkinson's disease cause bradyphrenia?
AUTHORS: Phillips JG; Schiffter T; Nicholls ME; Bradshaw JL; Iansek R; Saling LL
AUTHOR AFFILIATION: Department of Psychology, Monash University, Clayton, Vic, Australia. psy193g@alpha1.cc.monash.edu.au
SOURCE: J Gerontol A Biol Sci Med Sci 1999 Aug;54(8):M404-9
CITATION IDS: PMID: 10496546 UI: 99424865
ABSTRACT: BACKGROUND: Age-related declines in intellectual functioning have been linked to slower processing of information. However, any slowness with advancing age could simply reflect slower movement rather than impaired cognition. To assess any age-related decline in cognitive speed, we used an accuracy-based task that does not require a speeded motor response and that measures the time required to acquire information (inspection time). To identify possible biological mechanisms of cognitive slowing, this task was also applied to patients with Parkinson's disease, a basal ganglia disorder that reportedly causes bradyphrenia (slower thought processes).

METHODS: In one experiment, 16 young (mean age 22.4 years) and 16 older adults (mean age 71.6 years) matched for intelligence and education completed an inspection time task. The task required judgments as to order of onset of two lights, where the interval between onsets ranged from 20-250 msec. A second experiment compared 16 patients diagnosed with idiopathic Parkinson's disease and 16 age-matched controls upon the same task.

RESULTS: Older adults demonstrated significant cognitive slowing compared to younger adults. Medicated nondemented Parkinsonian patients were not impaired on this task compared to age-matched controls.

CONCLUSIONS: Clinical and empirical impressions of bradyphrenia in Parkinson's disease may instead reflect advancing age or slower movement, because the effects of age may be greater in some cases than the effects of basal ganglia disease once motor dysfunction has been allowed for.

1999/09
1999/25 09:00

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TITLE: Evolution of motor fluctuations in Parkinson's disease: a longitudinal study over 6 years.
AUTHORS: Reardon KA; Shiff M; Kempster PA
AUTHOR AFFILIATION: Department of Neurosciences, Monash Medical Centre, Clayton, Victoria, Australia.
SOURCE: Mov Disord 1999 Jul;14(4):605-11
CITATION IDS: PMID: 10435497 UI: 99361850
ABSTRACT: A prospective longitudinal 6-year study of 34 patients with Parkinson's disease from the time of initiation of drug treatment explored changes in the motor response to L-dopa over the early to mid disease course. Motor fluctuations developed in 41% after a mean L-dopa treatment interval of 25 months and dyskinesia developed in 53% after a mean of 15 months' treatment. Patients who developed fluctuations had a significantly better response to L-dopa than nonfluctuators. Nonfluctuators also had significantly greater "midline" motor disability affecting cranial and truncal muscles and gait. The development of motor fluctuations may simply reflect a retained capacity to respond to L-dopa as endogenous dopaminergic neurotransmission declines with progressive nigral cell loss. Many patients who show no sign of motor fluctuation 5 or 6 years into the disease course have a relatively blunted response to L-dopa. The proportion of such cases seems to correspond to the percentage that have coexisting striatal pathologic changes in postmortem studies.

1999/08
1999/06 10:00


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TITLE: Interdisciplinary rehabilitation in Parkinson's disease.
AUTHORS: Iansek R
AUTHOR AFFILIATION: Geriatric Research Unit, Kingston Centre, Cheltenham, Melbourne, Australia.
SOURCE: Adv Neurol 1999;80:555-9
CITATION IDS: PMID: 10410771 UI: 99338960
ABSTRACT: The use of a multidisciplinary team in managing end-stage PD was described, emphasizing the use of a specifically designed rehabilitation program based on current concepts of basal ganglia function and malfunction in PD as a means of unifying the team members, providing them with a common knowledge base and enabling the team members to speak to the patients with a common language. This approach has enabled the multidisciplinary team to function in an interdisciplinary and intradisciplinary manner.

1999/07
1999/20 10:00


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TITLE: Regulation of parkinsonian speech volume: the effect of interlocuter distance.
AUTHORS: Ho AK; Iansek R; Bradshaw JL
AUTHOR AFFILIATION: Neuropsychology Research Unit, Psychology Department, Monash University, Clayton 3168, Victoria, Australia. Aileen.Ho@sci.monash.edu.au
SOURCE: J Neurol Neurosurg Psychiatry 1999 Aug;67(2):199-202
CITATION IDS: PMID: 10406989 UI: 99337756
ABSTRACT: This study examined the automatic regulation of speech volume over distance in hypophonic patients with Parkinson's disease and age and sex matched controls. There were two speech settings; conversation, and the recitation of sequential material (for example, counting). The perception of interlocuter speech volume by patients with Parkinson's disease and controls over varying distances was also examined, and found to be slightly discrepant. For speech production, it was found that controls significantly increased overall speech volume for conversation relative to that for sequential material. Patients with Parkinson's disease were unable to achieve this overall increase for conversation, and consistently spoke at a softer volume than controls at all distances (intercept reduction). However, patients were still able to increase volume for greater distances in a similar way to controls for conversation and sequential material, thus showing a normal pattern of volume regulation (slope similarity). It is suggested that speech volume regulation is intact in Parkinson's disease, but rather the gain is reduced. These findings are reminiscent of skeletal motor control studies in Parkinson's disease, in which the amplitude of movement is diminished but the relation with another factor is preserved (stride length increases as cadence-that is, stepping rate, increases).

1999/07
1999/17 10:00


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TITLE: Gait consistency over a 7-day interval in people with Parkinson's disease.
AUTHORS: Urquhart DM; Morris ME; Iansek R
AUTHOR AFFILIATION: Spinal Management Clinics of Victoria, Peninsula Sports Medicine Centre, and Peninsula Community Health Service, Mornington, Australia.
SOURCE: Arch Phys Med Rehabil 1999 Jun;80(6):696-701
CITATION IDS: PMID: 10378498 UI: 99304843
ABSTRACT: OBJECTIVE: To evaluate the consistency of temporal and spatial parameters of the walking pattern in subjects with idiopathic Parkinson's disease (PD) over a 7-day interval during the "on" phase of the levodopa medication cycle.

SETTING: Walking patterns were measured on a 12-meter walkway at the Kingston Gait Laboratory, Cheltenham, using a computerized stride analyzer.

SUBJECTS: Sixteen subjects (7 women, 9 men) with PD recruited from the Movement Disorders Clinic at Kingston Centre.

MAIN OUTCOME MEASURES: Speed of walking, stride length, cadence, and the percentage of the walking cycle spent in the double limb support phase of gait were measured, together with the level of disability as indexed by the modified Webster scale.

RESULTS AND CONCLUSIONS: Product-moment correlation coefficients and intraclass correlation coefficients (ICC 2,1) for repeat measures over a 7-day interval were high for speed (r = .90; ICC = .93), cadence (r = .90; ICC = .86), and stride length (r = 1.00; ICC = .97) and moderate for double limb support duration after removal of outliers (r = .75; ICC = .73); 95% confidence intervals for the change scores were within clinically acceptable limits for all variables. The mean modified Webster score was 11.4 on the first day and 10.1 7 days later. The gait pattern and level of disability in subjects with PD without severe motor fluctuations remained stable over a 1-week period when optimal medication prevailed.

1999/06
1999/23 10:00


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TITLE: Movement-related potentials in Parkinson's disease: external cues and attentional strategies.
AUTHORS: Cunnington R; Iansek R; Bradshaw JL
AUTHOR AFFILIATION: Department of Psychology, Monash University, Clayton, Victoria, Australia.
SOURCE: Mov Disord 1999 Jan;14(1):63-8
CITATION IDS: PMID: 9918346 UI: 99114905
ABSTRACT: Hypokinetic movement can be greatly improved in Parkinson's disease patients by the provision of external cues to guide movement. It has recently been reported, however, that movement performance in parkinsonian patients can be similarly improved in the absence of external cues by using attentional strategies, whereby patients are instructed to consciously attend to particular aspects of the movement which would normally be controlled automatically. To study the neurophysiological basis of such improvements in performance associated with the use of attentional strategies, movement-related cortical potentials were examined in Parkinson's disease and control subjects using a reaction time paradigm. One group of subjects were explicitly instructed to concentrate on internally timed responses to anticipate the presentation of a predictably timed go signal. Other subjects were given no such instruction regarding attentional strategies. Early-stage premovement activity of movement-related potentials was significantly increased in amplitude and reaction times were significantly faster for Parkinson's disease subjects when instructed to direct their attention toward internally generating responses rather than relying on external cues. It is therefore suggested that the use of attentional strategies may allow movement to be mediated by less automatic and more conscious attentional motor control processes which may be less impaired by basal ganglia dysfunction, and thereby improve movement performance in Parkinson's disease.

1999/01
1999/26 03:01

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TITLE: Performance on clinical tests of balance in Parkinson's disease.
AUTHORS: Smithson F; Morris ME; Iansek R
AUTHOR AFFILIATION: Research Unit, Kingston Centre, Cheltenham, Victoria, Australia.
SOURCE: Phys Ther 1998 Jun;78(6):577-92
CITATION IDS: PMID: 9626270 UI: 98289510
ABSTRACT: BACKGROUND AND PURPOSE: Due to the high incidence of falls in people with idiopathic Parkinson's disease (PD), the assessment of standing balance is a key component of physical therapist evaluation. This study investigated performance on clinical tests of standing balance in subjects with and without PD.

SUBJECTS: The subjects were 10 persons with PD who had a history of falls (age range = 60-80 years), 10 persons with PD who had no history of falls (age range = 63-79 years), and 10 persons with no known neurological impairment (age range = 60-78 years) who served as a comparison group.

METHODS: Subjects were tested on their ability to maintain stability in 3 conditions: (1) steady standing (feet apart, feet together, tandem stance, step stance, and single-limb stance), (2) in response to perturbations generated by self-initiated movements (arm raise, functional reach, bend-reach, and step tests), and (3) in response to an external perturbation to upright stance (shoulder tug). Balance was measured at peak dosage in the levodopa medication cycle (in the morning) and 7 days later.

RESULTS: The mean Hoehn and Yahr Disability Scale score was 3.0 for the fallers with PD and 2.5 for the nonfallers with PD. Performance on the tandem stance, single-limb stance, functional reach, and shoulder tug tests demonstrated differences between the subjects with PD and the comparison group and between the fallers and nonfallers with PD. The results of these tests were highly repeatable over 7 days (ICC = .61-.94).

CONCLUSION AND DISCUSSION: Although there was a small sample size, performance was highly consistent across 7 days when testing occurred during peak dosage of levodopa. A small battery of tests were sensitive enough to discriminate between people with PD who fall and those with no history of falls.

1998/06
1998/17 02:03

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TITLE: Bimanual co-ordination in Parkinson's disease.
AUTHORS: Johnson KA; Cunnington R; Bradshaw JL; Phillips JG; Iansek R; Rogers MA
AUTHOR AFFILIATION: Department of Psychology, Monash University, Clayton, Victoria, Australia.
SOURCE: Brain 1998 Apr;121 ( Pt 4):743-53
CITATION IDS: PMID: 9577398 UI: 98238259
ABSTRACT: The basal ganglia may be involved in bimanual co-ordination. Parkinson's disease (which impairs basal ganglia output) is clinically reported to cause difficulties in the performance of co-ordinated bimanual movements. Nevertheless, any bimanual co-ordination difficulties may be task specific, as experimental observations are equivocal. To infer the role of the basal ganglia in co-ordinating the two arms, this study investigated the bimanual co-ordination of patients with Parkinson's disease. Sixteen Parkinson's disease patients and matched control subjects performed a bimanual cranking task, at different speeds (1 and 2 Hz) and phase relationships. All subjects performed the required bimanual in-phase movement on a pair of cranks, at fast (2 Hz) and slow (1 Hz) speeds. However, the Parkinson's disease patients were unable to perform the asymmetrical anti-phase movement, in which rotation of the cranks differed by 180 degrees, at either speed; but instead reverted to the in-phase symmetrical movement. For Parkinson's disease patients, performance of the in-phase movement was more accurate and stable when an external timing cue was used; however, for anti-phase movement, the external cue accentuated the tendency for patients to revert to more symmetrical, in-phase movements.

1998/05
1998/13 02:02

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TITLE: Abnormalities in the stride length-cadence relation in parkinsonian gait.
AUTHORS: Morris M; Iansek R; Matyas T; Summers J
AUTHOR AFFILIATION: Kingston Centre, Cheltenham, Australia.
SOURCE: Mov Disord 1998 Jan;13(1):61-9
CITATION IDS: PMID: 9452328 UI: 98112707
ABSTRACT: The purpose of this investigation was to clarify abnormalities in the stride length-cadence relation in gait hypokinesia in Parkinson's disease (PD). A second aim was to investigate the effect of levodopa medication on the foot-step pattern. In the first experiment, 20 subjects with idiopathic PD and 20 age-, sex-, and height-matched controls performed a series of 10 m walking trials at cadence rates ranging from 40 steps/min to 180 steps/min. Cadence rates were set by an electronic metronome, and gait patterns were measured by using a footswitch stride-analyzer system. By instructing subjects to concentrate on walking in time to the metronome beat, the baseline stride length could be monitored for a range of velocities with the compensatory effects of cadence removed. Linear-regression analysis revealed that the mean slope for the regression of stride length against cadence was not different from normal in PD, although there was a statistically significant difference in mean intercept between the PD group (0.25) and the control group (0.59); [t (19) = -4.76; p = 0.0001]. The second experiment evaluated the effects of levodopa on stride-length regulation in 10 subjects with idiopathic PD on average 45 min before and after the first morning dose was administered. There was a statistically significant increase in stride length for all cadence rates from premedication to postmedication phases and the maximal stride length was achieved at higher cadence rates after medication. The slope of the regression of stride length against cadence did not alter according to medication status, although the mean intercept was significantly lower before levodopa (-0.06) compared with after levodopa (0.27); [t (9) = -3.83; p = 0.004]. These results suggest that defective scaling of stride length underlies gait disturbance in PD.

1998/02
1998/06 05:53



TITLE: Movement-related potentials in Parkinson's disease. Motor imagery and movement preparation.
AUTHORS: Cunnington R; Iansek R; Johnson KA; Bradshaw JL
AUTHOR AFFILIATION: Department of Psychology, Monash University, Clayton, Victoria, Australia.
SOURCE: Brain 1997 Aug;120 ( Pt 8):1339-53
CITATION IDS: PMID: 9278627 UI: 97424514
ABSTRACT: Movement-related potentials (MRPs) associated with voluntary movements reflect cortical activity associated with processes of movement preparation and movement execution. Early-stage pre-movement activity is reduced in amplitude in Parkinson's disease. However, it is unclear whether this neurophysiological deficit relates to preparatory or execution-related activity, since previous studies have not been able to separate different functional components of MRPs. Motor imagery is thought to involve mainly processes of movement preparation, with reduced involvement of end-stage movement execution-related processes. Therefore, MRP components relating to movement preparation and execution may be examined separately by comparing MRPs associated with imagined and actual movements. In this study, MRPs were recorded from 14 subjects with Parkinson's disease and 10 age-matched control subjects while they performed a sequential button-pressing task, and while they imagined performance of the same task. Early-stage pre-movement activity was present in both Parkinson's disease patients and control subjects when they imagined movement, but was reduced in amplitude compared with that for actual movement. Movement execution-related components, arising predominantly from the primary motor cortex, were relatively unaffected in Parkinson's disease subjects. However, motor preparatory processes, probably involving the supplementary motor area, were reduced in amplitude overall and abnormally prolonged, indicating impaired termination following the motor response. Further, this impaired termination of preparatory-phase activity was observed only in patients with more severe parkinsonian symptoms, and not in early-stage Parkinson's disease.

1997/08
1997/01 00:00

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