Date of Award

2007

Degree Type

Thesis

Degree Name

Master of Science

Program

Physiology

Supervisor

Dr. Brian Corneil

Second Advisor

Dr. Jonathan Hore

Third Advisor

Dr. Stan Leung

Abstract

High-frequency bursts within the deeper layers of the primate superior colliculus (dSC) encode desired eye-head gaze shifts. In addition, many dSC neurons emit earlier low-frequency activity. We hypothesized that low-frequency activity in dSC neurons contributes to priming and orienting the head in advance of eye-head gaze shifts. We simultaneously recorded dSC unit discharge and electromyographic (EMG) activity of dorsal neck muscles from three rhesus monkeys performing a gap-saccade paradigm with different levels of reward expectancy. As reward expectancy increased, low-frequency dSC activity increased and EMG activity from the contralateral obliquus capitis inferior (OCI) muscle also increased. These measures were positively correlated, with the optimal correlation occurring when EMG activity was delayed by 14 ms. These results support the hypothesis that low-frequency dSC activity constitutes a motor command, which functions in head control prior to upcoming gaze shifts.

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