Project 171056

Humans and other primates are predominantly visual animals. Our dependency on vision necessitated the development of a refined oculomotor system to rapidly change our line of sight (gaze shifts). Large gaze shifts frequently require coordinated movements of both the eyes and the head. Sometimes, the exact same gaze shift can be generated by using just the eyes, by pairing eye movement with a large head movement, or any combination in between. The overall objective of my work is to understand how the brain flexibly coordinates the eyes and head during gaze shifts. The key hypothesis is that the oculomotor brainstem is endowed with two levels: a higher level surpassed when a commitment to shift gaze is made, and a lower level that permits head movements without gaze shifts. By selectively controlling neural activity relative to these differential levels, the brain can appropriately coordinate the eyes and head in different contexts. Such contexts can be divided into top-down processes based on a subject's prior knowledge or expectations, and bottom-up processes stemming from incoming sensory information, such as those related to stimulus position. A recurring theme of my research is that the head is not subjected to the same control that dictates eye movements. Our hypothesis predicts that close assessment of the neural control of the head, via recording of the activity of neck muscles, may provide direct insights into the oculomotor system on a millisecond timescale. An exciting implication of this prediction is that it is readily transferable to humans. If true, neck muscle recordings in humans may provide a quantifiable measure of the oculomotor system at a temporal resolution only currently possible in animals. Such a tool could be helpful in assessing a variety of clinical conditions, such as neglect syndromes following parietal strokes.

using neck muscle recordings to study the neural control of eye-head gaze shifts