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Small saccades restrict visual scanning area in Parkinson's disease

Authors


  • Relevant conflicts of interest/financial disclosures: Nothing to report.

  • Yasuo Terao is supported by supported by a Research Project Grant-in-aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology of Japan Research and GlaxoSmithKline and Boehringer Ingelheim and has received speaker's honoraria from Boehringer Ingelheim. Ritsuko Hanajima is supported by a Research Project Grant-in-aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology of Japan Research and has received speaker's honoraria from Medtronic Japan Co., Ltd.; Novartis Japan Co., Ltd.; and Dainippon Sumitomo Pharma. Co., Ltd. Yoshikazu Ugawa is supported by a Research Project Grant-in-aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology of Japan Research; by grants for the Research Committee on the Best rTMS Treatment of Parkinson's Disease from the Ministry of Health and Welfare of Japan; by the Research Committee on Dystonia of the Ministry of Health and Welfare of Japan; and by a grant from the Committee of the Study of Human Exposure to EMF from the Ministry of Public Management, Home Affairs, Post and Telecommunications. Hideyuki Matsumoto, Toshiaki Furubayashi, Akihiro Yugeta, Hideki Fukuda, and Masaki Emoto have no disclosures. Full financial disclosures and author roles may be found in the online version of this article.

Abstract

The purpose of this study was to investigate abnormalities in visual scanning when Parkinson's disease patients view images of varying complexity. Eighteen nondemented Parkinson's disease patients and 18 normal subjects participated in the study. The ocular fixation position during viewing visual images was recorded using an eye-tracking device. The number of saccades, duration of fixation, amplitude of saccades, and scanned area in Parkinson's disease patients were compared with those in normal subjects. We also investigated whether the number of saccades, duration of fixation, or amplitude of saccades influenced the scanned area. While scanning images of varying complexity, Parkinson's disease patients made fewer saccades with smaller amplitude and longer fixation compared with normal subjects. As image complexity increased, the number of saccades and duration of fixation gradually approached those of normal subjects. Nevertheless, the scanned area in Parkinson's disease patients was consistently smaller than that in normal subjects. The scanned area significantly correlated with saccade amplitude in most images. Importantly, although Parkinson's disease patients cannot make frequent saccades when viewing simple figures, they can increase the saccade number and reduce their fixation duration when viewing more complex figures, making use of the abundant visual cues in such figures, suggesting the existence of ocular kinesie paradoxale. Nevertheless, both the saccade amplitude and the scanned area were consistently smaller than those of normal subjects for all levels of visual complexity. This indicates that small saccade amplitude is the main cause of impaired visual scanning in Parkinson's disease patients. © 2011 Movement Disorder Society

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