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Title page for ETD etd-12032009-110833


Type of Document Dissertation
Author Cohen, Jeremiah Yaacov
Author's Email Address jeremiah.cohen@gmail.com
URN etd-12032009-110833
Title Neural coding and timing of visual target selection in the frontal eye field
Degree PhD
Department Neuroscience
Advisory Committee
Advisor Name Title
Mark T. Wallace Committee Chair
Jeffrey D. Schall Committee Member
Martin Paré Committee Member
René Marois Committee Member
Keywords
  • visual search
  • decision making
  • target selection
  • frontal eye field
Date of Defense 2009-11-30
Availability unrestricted
Abstract
How does the brain select visual targets for eye movements? We recorded neural activity while macaques performed visual search in which they were trained to move their eyes to a target stimulus among an array of distractor stimuli for a reward. Three signals were used to measure the relationship between the decision to move the eyes to a target and neural activity: spike rates from neurons in the frontal eye field (FEF), local field potentials from FEF, and event-related potentials recorded from the skull. We found that (1) FEF neurons cooperated and competed to select visual targets, measured using correlations between spike times of simultaneously recorded neurons, (2) FEF neurons interacted more when the visual search task was easier (i.e., the target and distractors were easily discriminable), measured using a multivariate analysis and decreased firing variability before eye movements, (3) FEF neurons decreased firing variability around the time of target selection by the mean firing rate, (4) FEF neurons were distinguished both functionally and biophysically, on the basis of action potential width, (5) FEF selected search targets from distractors before the macaque homologue of a human cognitive event-related potential (the N2pc) that marks the allocation of attention, and (6) the time between visual search array presentation and the time that FEF neurons discriminated between target and distractors was later when there were more stimuli the animal needed to choose from.
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