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NEURAL CORRELATES OF RANDOM AND INFORMED SACCADIC CHOICES IN THE MACAQUE FRONTAL EYE FIELDS AND CENTRAL THALAMUS

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abstract
The motor thalamus (OcTh) constitutes the penultimate synapse of a putative oculomotor feedback loop that originates in and returns to the frontal eye fields (FEF). To examine how this circuit may contribute to saccade target selection, neural correlates of perceptual judgment and motor choice were evaluated for visuomotor neurons recorded in the FEF and OcTh. Monkeys performed a compelled-saccade task, a two-alternative forced-choice task that requires rapid perceptual judgments (color discrimination) and which, by design, decouples the time of saccade initiation from the time course of the perceptual decision. By controlling perceptual processing time (PT), or stimulus viewing time, the task yields both random and informed saccadic choices such that performance, i.e., the probability of discriminating target from distracter, increases from chance to nearly perfect with increasing PT. Our findings demonstrate that perceptual information favors correct choices both by accelerating (correct) and decelerating (incorrect) ongoing motor plans, and that the neural signature of this process resides in marked differences in the timing of neural differentiation for random and informed choices. The general pattern of findings was very similar for the FEF and OcTh, with neural differentiation for visuomotor neurons in both areas illustrating a characteristic dependence on PT: for uninformed choices (short PTs), the activities of visuomotor neurons reflected only motor selection, whereas for informed choices (long PTs), they displayed a distinctive combination of motor choice and incoming sensory information (target-related acceleration / distracter-related deceleration). The findings suggest qualitatively similar neural correlates of evolving perceptual decision and motor choice within FEF and OcTh, successive nodes in a putative cortico-subcortical loop. For visuomotor neurons in both structures, perceptual information disambiguates the initial conflict associated with choosing one of the two alternatives, and both the intensity of the conflict and the time at which it is resolved are consistent with the interplay of sensory and motor processes as determined by the unique temporal demands of the compelled-saccade task. Similarities between the cortical and thalamic findings lend further support to the hypothesis that cortico-subcortical interactions contribute to the perceptual decision-making process.
subject
central thalamus
decision making
electrophysiology
frontal eye field
saccade
vision
contributor
Costello Grinberg, Maria Gabriela (author)
Stanford, Terrence R. (committee chair)
Laurienti, Paul (committee member)
Constantinidis, Christos (committee member)
Ramachandran, Ramnarayan (committee member)
date
2012-09-05T08:35:18Z (accessioned)
2012 (issued)
degree
Neurobiology & Anatomy (discipline)
10000-01-01 (liftdate)
embargo
forever (terms)
identifier
http://hdl.handle.net/10339/37434 (uri)
language
en (iso)
publisher
Wake Forest University
title
NEURAL CORRELATES OF RANDOM AND INFORMED SACCADIC CHOICES IN THE MACAQUE FRONTAL EYE FIELDS AND CENTRAL THALAMUS
type
Dissertation

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