The Control of Gaze Orientation in Primates: Neural Circuitry and Computational Mechanisms

Eric Mousset

School of Electrical and Information Engineering, University of Sydney

Tuesday 29 February at 11am

Abstract

We present a review of research on the neural basis of gaze orientation in primates and contrast the most recent theories. Particular attention is given to studies involving comparisons of head-fixed and head-free gaze shifts, from both experimental and computational modelling perspectives. Our own modelling results are also presented, accounting for combined head- and eye-movements in simple ocular saccade and gaze shift tasks. The main issue addressed in the present study concerns the way a visually-induced desired gaze shift is encoded and how the corresponding task is distributed between the motor control of head- and eye-movements. The model includes intrinsic circuitry and mutual influences of pathways between Superior Colliculus (SC) intermediate gray layer, brainstem paramedian pontine reticular formation (PPRF), Cerebellum (Cb) and Parietal Cortex. Neck motoneurons are under the control of the Cb whereas ocular ones are driven by the brainstem burst generator. Eye-movements are regulated through a dynamic motor-error control feedback loop that is local to the PPRF; the latter loop being part of a broader control mechanism involving SC and Cb. Simulation results are provided, accounting for saccade dysmetria through cerebellar lesion, distortion of the curvature of the saccadic trajectory through reversible deactivation of caudal SC saccade-control related cells, gain adaptation of the eye-movement amplitude, interruption of saccades through direct electrical stimulation of either rostrally-located SC fixation cells or NRTP omnipause neurons, and effects of electrical stimulations of caudal SC saccade-related burst neurons on saccade dynamics.

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last updated December 01, 2003 10:37 AM
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