Saccadic eye movements in Parkinson’s disease: an eye-tracking and fMRI study (P1.321)

OBJECTIVE:We sought to investigate reflexive and volitional saccadic eye movements in Parkinson’s disease (PD) patients, focusing on the effect of dopaminergic medication upon saccadic behavioural performance and perisaccadic functional brain activity.BACKGROUND:Studies addressing the effect of dopaminergic medication on saccadic performance of PD patients have shown inconsistent findings, demonstrating small or no effect on latency, amplitude and/or success rate of saccades. Additionally, few studies to date have investigated the functional anatomy of the saccade-related cortical control in PD.DESIGN/METHODS:We examined reflexive (prosaccades, PS) and volitional (anti-saccades, AS) eye movements in the vertical and horizontal directions with eye tracking (SMI iViewX, 500Hz) in PD patients on (onPD; n=23) and off (offPD; n=19) their medication on the experiment day, and compared them with controls (CTs; n=22). We further measured perisaccadic blood oxygenation-level dependent (BOLD) activation in these groups by performing a block-design functional Magnetic Resonance Imaging (fMRI) study, consisting of two runs (PS, AS) of 6 blocks each (3 vertical and 3 horizontal).RESULTS:Behavioural saccadic data including latency, amplitude, peak velocity, and success rate of PS and AS showed no statistically significant differences between groups (p=0.083, MANOVA). Functional imaging data (ASu003ePS between groups effects analysis) demonstrated greater activation in dorsomedial prefrontal cortex in onPD and offPD groups when compared with CTs; comparison between onPD and offPD groups revealed higher activation in occipital and posterior parietal lobes in the former group (pu003c0.01, GLM).CONCLUSIONS:While saccadic behavioral performance appeared to be similar between Parkinson’s disease patients and controls, higher neuronal activation in frontal areas in PD patients might reflect a compensatory strategy to basal ganglia impairment, this way maintaining normal behavioural performance. Greater activation in posterior areas in PD patients on-meds could reflect drug-related aberrant activation that may not bring about a behavioral benefit. Disclosure: Dr. Lemos has nothing to disclose. Dr. Pereira has nothing to disclose. Dr. Almendra has nothing to disclose. Dr. Rebelo has nothing to disclose. Dr. Castelhano has nothing to disclose. Dr. Cunha has nothing to disclose. Dr. Januario has nothing to disclose. Dr. Freire has nothing to disclose. Dr. Cunha has nothing to disclose. Dr. Castelo-Branco has nothing to disclose.