Objective: To investigate suppression of automatic movements and execution of voluntary motor commands in an early stage Huntington’s disease patients.

Background: The ability to suppress automatic movements and to plan and execute voluntary motor commands is controlled by circuitry that includes the Basal Ganglia (BG). BG form loops with cortical regions including the Dorsolateral Prefrontal Cortex (DLPC), which is involved in control of cognitive and behavioural processes, including the voluntary control of saccades. These abilities could involve projections from the DLPC to the superior colliculus via the BG, which sustains striatal neurodegeneration in Huntington’s disease (HD). Patients with HD show oculomotor impairments that could be related to the disruption of the aforementioned circuits. To test this hypothesis, we studied the execution of pro- and anti-saccades in early-stage HD patients (HDP).

Methods: 23 HD patients (49.6 y/o ±11.4); disease duration (4.5±2.9 y), and 23 healthy matched controls, performed the Interleaved Pro- / Anti-Saccade Task. The Pro-Saccade (PS) task requires making an automatic saccade to a visual stimulus, whereas the Anti-Saccade (AS) task requires making a voluntary saccade to the opposite direction. We computed group differences for mean reaction time (SRT), coefficient of variation; anticipatory, express, regular and corrective saccades; direction errors, amplitude, peak velocity and duration. These variables were also correlated to disease severity with the UHDRS.

Results: Our analyses confirmed previous PS and AS deficits in HDP. Additionally, we showed significant differences in AS performance in regular saccades, anticipatory saccades, and corrective saccades. UHDRS motor scale showed positive correlations with PS SRT, regular saccade errors in AS; and negative correlations with amplitude in PS and AS. UHDRS functional scale showed positive correlation with saccade amplitude in AS; and negative correlation with regular errors in AS, and PS SRT.

Conclusions: Our analyses of HDP for AS showed specific voluntary control saccades deficits not present in PS. In later stages of HD, AS and PS impairments were similar to those previously reported. These results confirm a critical role of the BG-cerebral cortex loops in the voluntary control for the initiation and suppression of saccades.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/interleaved-pro-and-anti-saccade-performance-in-huntingtons-disease/