The Role of the Frontal Eye Fields in Pursuit Learning

University Of California, San Francisco, San Francisco CA

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Abstract

DESCRIPTION (provided by applicant): An important aspect of motor learning is the accurate timing of movements. Smooth pursuit is an excellent behavior to study how the brain produces temporally precise learned movements. A pursuit target consistently changes its direction a fixed amount of time after it starts moving (the learning time). Upon repeated exposure to this stimulus, subjects leam to modify their smooth eye movement around the learning time. We propose to look for neural signals that control the timing of the learned eye movement in the smooth pursuit region of the frontal eye fields (FEFSEM). Different FEFSEM neurons are preferentially active during distinct temporal segments of smooth pursuit. In this proposal, we test the prediction, supported by our preliminary data, that changes in mean firing rate during learning are concentrated in FEFSEM neurons that prefer a temporal segment of pursuit around the learning time. First, we will compare changes in mean firing rate for the same learning time across neurons that prefer different temporal segments of pursuit. We will then examine how individual neurons modulate their firing rate during two separate learning blocks whose only difference is when the target changes direction. Our second goal is to determine whether learning modulates how different FEFSEM neurons contribute to the eye movement. The trial-by-trial correlation between the neural response and the behavioral response measures the extent to which a neuron's output reflects a motor signal that is shared across the neural population, and is therefore a valuable tool for assessing the functional properties of the population. Shifts in the neuron-behavior correlation can be attributed to a limited number of factors, including changes in the weighting of the neuron, the size of the neural pool that drives the eye movement, or the amount of neural synchrony within the pool. Combining the results from aim 1 and aim 2 will shed light on how learning alters the activity of FEFSEM neurons and their relationship to behavior. Many patients suffering from neurological disorders that involve frontal lobe dysfunction, such as Alzheimer's disease and frontotemporal dementia, exhibit striking oculomotor deficits. A better understanding of the role of the frontal cortex in oculomotor control may provide insight into how specific frontal circuits are disrupted in these diseases. A critical function of the healthy brain is to produce and control movements. Understanding how different parts of the brain are involved in motor control can help us safely diagnose problems with these brain regions by examining a patient's performance on simple motor tasks.