Eye movement control during visual pursuit in Parkinson's disease.

Chia-Chien Wu,Robert D Salazar,Veena Dali,Alice Cronin-Golomb,Marc Pomplun,Arash Yazdanbakhsh,Olivier J Barthelemy,Bo Cao,Celia Gagliardi

doi:10.7717/peerj.5442

Chia-Chien Wu, Robert D Salazar + Show 7 more

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https://doi.org/10.7717/peerj.5442

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Abstract

BackgroundPrior studies of oculomotor function in Parkinson’s disease (PD) have either focused on saccades without considering smooth pursuit, or tested smooth pursuit while excluding saccades. The present study investigated the control of saccadic eye movements during pursuit tasksand assessed the quality of binocular coordinationas potential sensitive markers of PD.MethodsObservers 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 further investigate binocular coordination, the moving target was presented on both eyes (binocular condition), or on one eye only (dichoptic condition).ResultsThe PD group made more saccades than age-matched normal control adults (NC) both during fixation and pursuit. The difference between left and right gaze positions increased over time during the pursuit period for PD but not for NC. The findings were not related to age, as NC and young-adult control group (YC) performed similarly on most of the eye movement measures, and were not correlated with classical measures of PD severity (e.g., Unified Parkinson’s Disease Rating Scale (UPDRS) score).DiscussionOur results suggest that PD may be associated with impairment not only in saccade inhibition, but also in binocular coordination during pursuit, and these aspects of dysfunction may be useful in PD diagnosis or tracking of disease course.

Highlights

Parkinson’s disease (PD) is a complex neurodegenerative disorder characterized by the cardinal motor signs of tremor, rigidity, bradykinesia, disordered gait, balance, and posture (Massano & Bhatia, 2012; Rodriguez-Oroz et al, 2009)
Similar to what we found in the binocular condition (Fig. 6), many PD showed an increase in the binocular divergence after pursuit was initiated, whereas most of normal control adults (NC) and young-adult control group (YC) remained at the same level
Saccades are often excluded from smooth pursuit analysis as seen in many previous studies, yet they reveal how attention may be distributed during pursuit (Heinen, Jin & Watamaniuk, 2011; Jin et al, 2013), and provide valuable information about the control of the oculomotor system in PD, as we show with the present experimental results

Summary

Introduction

Parkinson’s disease (PD) is a complex neurodegenerative disorder characterized by the cardinal motor signs of tremor, rigidity, bradykinesia, disordered gait, balance, and posture (Massano & Bhatia, 2012; Rodriguez-Oroz et al, 2009). Individuals with PD have difficulty in moving the limbs and trunk, as well as in controlling oculomotor function. It has been known for some time that those with PD show prolonged saccadic latency (Rascol et al, 1989) and reduced smooth pursuit gain relative to healthy age-matched. Many other studies have reported perceptual and visuospatial disturbance in PD (Bodis-Wollner, 2003; Cronin-Golomb, 2010; Davidsdottir, Cronin-Golomb & Lee, 2005; Davidsdottir et al, 2008; Diaz-Santos et al, 2015) It is still unclear whether these oculomotor symptoms may co-occur with, or even arise before, the disease-characteristic motor symptoms in limbs and trunk. Discussion: Our results suggest that PD may be associated with impairment in saccade inhibition, and in binocular coordination during pursuit, and these aspects of dysfunction may be useful in PD diagnosis or tracking of disease course

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