P.060 Altered oculomotor learning in thalamic stroke patients

Abstract

Background: Visuomotor learning can be elicited experimentally by displacing the target of a saccade during the ongoing eye movement. In healthy subjects, the resulting mismatch between expected and experienced visual error after saccade completion elicits a gradual adaptation of saccade amplitude. The goal of this project was to explore the role of cerebro-thalamo-cerebellar circuits in the dynamics of visuomotor learning. Methods: Patient RK is a 38-year-old right hand dominant male who suffered a focal thalamic stroke of the right thalamus, confined to ventral lateral posterior and ventral medial nuclei. We employed a standard saccadic adaptation paradigm and assessed dynamics of visuomotor learning by fitting a simple state-equation to saccade amplitudes towards the ipsi- and contralesional hemifield. Results: While RK was able to adapt saccade amplitudes in both directions, adaptation dynamics were different for leftward versus rightward saccades. Rightward, ipsilesional saccades exhibited a lower learning rate but similar retention of altered saccade metrics, compared to leftward, contralesional saccades. Conclusions: The present study assessed a patient with a focal lesion to the right cerebellar thalamus on a saccade adaptation paradigm. Results demonstrated slower visuomotor learning for saccades into the ipsilesional hemifield, suggesting an important contribution of cerebello-cortical projections mediated by thalamic relays for visuomotor learning.