Movement vigor: consistency, conservation, and modulation

This thesis is devoted to a better understanding of the vigor with which primates perform everyday actions. Indeed, there are great differences in baseline amounts of movement vigor across individuals. However, vigor depends upon the environment, and the reward landscape. The first portion of this text focuses on the effects that the reward landscape has on movement vigor. Chapter 2 demonstrates the effect of rate of reward on vigor, in particular reaction time and peak velocity. In Chapter 3, we analyze the effects of monetary reward offerings on saccade vigor. We show that choice preference for one reward over another is manifest in saccade vigor at the time of decision. We also show that saccade vigor tracks the decision making process, with a steep drop in vigor once a decision is made. Finally, in Chapter 4, we investigate changes in movement vigor during combined head-free gaze shifts and reaching movements. The objective is threefold: 1. Analyze consistency of head and reaching movements within an individual, across days; 2. Analyze conservation of movement vigor within an individual, across movement modalities; and 3. Assess modulation of movement vigor as a function of time, to determine if changes in one modality predict simultaneous changes in other modalities.