Involuntary Saccadic Control in Parkinson’s disease

Arash Yazdanbakhsh¹, Chia-Chien Wu², Veena Dali³, Celia Gagliardi4, Oliver J. Barthelemy5, Bo Cao6, Marc Pomplun7, Alice Cronin-Golomb8
¹Boston University, ²Boston University, ³Boston University, 4Boston University, 5Boston University, 6University of Texas Health Science Center at Houston, 7University of Massachusetts Boston, 8Boston University

Prior studies of oculomotor function in Parkinson’s disease (PD) have either focused on saccades without considering smooth pursuit, or tested smooth pursuit while excluding any involuntary saccades. The present study investigated whether these involuntary saccades could serve as a useful biomarker for PD. Participants included 6 individuals with PD and 6 age-matched normal control participants (NC). Observers fixated on a central cross while a target moved toward it. Once the target reached the fixation cross, observers began to pursue the moving target. To vary the difficulty of fixation and pursuit, the moving target was presented on a blank, still, or moving background. The still background consisted of uniformly distributed stationary dots. The moving background was similar to the still background except that all the dots moved in either the same or the opposite direction of the target once the target reached the central fixation cross. TO investigate binocular coordination, each background condition was presented under a binocular condition, in which both eyes saw the same stimulus, and under a dichoptic condition, in which one eye saw only the target and the other eye saw only the background. The results showed that for all three backgrounds, PD made more involuntary saccades than NC during fixation and pursuit. Interestingly, the difference between the left and right eye positons increased over the time during the pursuit period for PD but not for NC. These results suggest that PD may be impaired not only in saccade inhibition, but also in binocular coordination during pursuit.

Keywords: Parkinson's Disease, Eye Movements

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