Neural Basis of Gaze Shifts

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DESCRIPTION (provided by applicant): Humans and nonhumans alike interact with the environment by orienting to objects of interest. Such responses are typically generated by integrating movements across multiple effectors. The long- term objective of the research program is to understand the coordinated eye-head movements that produce a change in the line of sight (gaze). The specific aims are designed to delineate feedforward, feedback and interactive mechanisms that result in the coordinated control of two different groups of muscles. A gaze shift is thought to be triggered by a command encoding the desired change in gaze, and structures in the brain stem determine the eye and head components required to generate the gaze shift. Specific Aim 1 seeks to identify where in the pontine reticular formation are the separate commands of eye and head movement control formulated. Head-restrained saccadic eye movements are controlled by an error-sensing feedback circuit that preserves its accuracy. Specific Aim 2 will investigate how the feedback principle extrapolates to head-unrestrained gaze shifts. Does it preserve accuracy of the gaze signal or just its saccadic eye component? Specific Aim 3 will test whether head movement commands can influence the dynamics of the eye component of gaze shift. Specific Aim 4 will revisit the gain of the vestibulo-ocular reflex during gaze shifts by evaluating the saccadic input into the extraocular motoneurons during gaze shifts. Overall, the results of these experiments will provide insights into the neural control of gaze shifts and offer diagnostic value for deficits resulting from oculomotor, vestibular and cervical disorders.