Master's Theses

Date of Award

2014

Document Type

Thesis

Department

Biomedical Engineering

First Advisor

Mitchell B. Schaffler

Second Advisor

Kelly

Keywords

Saccades, electroencephalography, cortex

Abstract

Saccades are rapid eye movements that allow us to focus the fovea on different parts of our visual environment. Many psychophysical studies have shown that subjects can discriminate stimuli presented at the saccadic target better than at any other location before an eye movement is made. It is believed that covert attention allotted to the intended destination of a saccade, called pre-saccadic attention, accounts for the improved discrimination of stimuli. Covert top-down attention, which consists of orienting your attention, and not your gaze, to an object in your visual periphery, is known to facilitate behavioral performance in a manner similar to that seen with eye movement planning. It is not known how the mechanisms governing these two processes differ. While covert top-down attention has been studied electrophysiologically, pre-saccadic attention has only been studied behaviorally in humans due to technical challenges. We overcame these challenges with an innovative paradigm to elucidate the neural correlates of pre-saccadic attention using electroencephalography (EEG). Event related potentials were compared for attended and unattended stimuli in three tasks: one involving saccades only, one involving saccades and a perceptual task, and one involving a perceptual task without eye movements. We found that it is unlikely that the primary visual cortex is the location at which visual processing is modulated by attention. More feasible candidates include the extrastriate and parietal cortex.

 
 

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