Representations of eye and image velocity in motion sensitive cortex

In order to successfully pursue a moving target, the oculomotor system must make accurate computations about both the velocity of image motion on the retina and the ongoing velocity of the eye. In sensory areas, such as primary visual cortex and the middle temporal area (MT), the responses of neurons to different image velocities have been examined in some detail. However, the responses of neurons to image velocities in later cortical areas have been comparatively less studied. Further, although neurons in some parts of cortex, including the medial superior temporal area (MST) are known to be sensitive to the direction of pursuit, their responses to different pursuit velocities have not been studied.;The thesis will begin with a series of behavioral experiments suggesting that the neurons sensitive to pursuit direction are likely also sensitive to pursuit velocity. In chapter 2, I will describe the responses of MST neurons during different pursuit and image velocities. Chapter 3 will detail how the responses of eye velocity tuned neurons might be combined to generate an accurate population estimate of eye velocity. Chapter 4 will explore how visual responses in MST change when the illusion of smooth motion is generated using apparent motion stimuli. The surprising response of MST neurons to these stimuli suggests that the neurons may be using a center-of-mass computation to decode responses from area MT. In the final chapter, I will use antidromic stimulation to ask whether the MST neurons projecting to the smooth eye movement region of the frontal eye fields are distinct from the general population.