Inhibitory control during smooth pursuit in Parkinson's disease and Huntington's disease |
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Authors: | Tracy Henderson BA Nellie Georgiou‐Karistianis BSc PhD Owen White MBBS PhD FRACP Lynette Millist BApSci David R. Williams MBBS PhD FRACP Andrew Churchyard BSc MBBS FRACP PhD Joanne Fielding BA BSc PhD |
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Affiliation: | 1. School of Psychology and Psychiatry, Clayton Campus, Monash University, Victoria, Australia;2. Department of Neurology, Royal Melbourne Hospital, Victoria, Australia;3. Van Cleef Roet Centre for Nervous Diseases, Faculty of Medicine, Nursing and Health Sciences, Monash University, Victoria, Australia;4. Huntington's Disease Unit, Bethlehem Hospital, Victoria, Australia |
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Abstract: | The basal ganglia are involved in the preferential selection and suppression of competing responses. Parkinson's disease and Huntington's disease are 2 prototypical basal ganglia disorders that feature impaired inhibitory control, a function of poor conflict resolution. Previous saccadic studies showed that individuals with Parkinson's disease experience difficulty suppressing unwanted ocular motor responses, whereas evidence for a similar difficulty in Huntington's disease is more equivocal. Relative to saccades, few research studies have examined inhibitory control processes in the context of an ongoing smooth pursuit task. In this study, we examined the ability of 16 patients with Parkinson's disease and 12 patients with Huntington's disease to suppress automatic responses to irrelevant distracters that transiently appeared during the tracking of a moving visual stimulus. Compared with an equivalent number of age‐matched controls, patients with Parkinson's disease generated proportionately more saccades to distracter stimuli. This was particularly evident for distracters appearing far away from the target. Conversely, whereas individuals with early‐stage Huntington's disease and healthy controls made a comparable number of errors toward distracter stimuli, those in a more advanced clinical stage demonstrated significantly poorer inhibitory control. The current findings in parkinsonian patients replicate those previously reported in the saccadic and manual response literature, demonstrating difficulty inhibiting a competing motor response. However, in Huntington's disease we demonstrate for the first time that inhibitory control declines in more advanced‐disease stages. This suggests that ocular motility may provide a sensitive marker of clinical disease progression in Huntington's disease. © 2011 Movement Disorder Society |
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Keywords: | inhibition attention Parkinson's disease Huntington's disease smooth pursuit |
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