Honors Theses (Biology)

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Peripheral Visuospatial Attention: An fMRI Study
(2005-09-30T16:05:57Z) Dugan, James Patrick
We used functional magnetic resonance imaging (fMRI) to demonstrate the effects of directing sustained attention to near and far peripheral locations ( <12 and >20 degree eccentricities, respectively) on blood oxygen level dependent (BOLD) response. Using a Hillyard paradigm we presented 8 Hz flashing light stimuli at 8, 12, 22, and 33 degree eccentricities in the upper left and right quadrants of the visual field. The 8 and 12 degree locations were presented randomly using a projection system. In a separate session the 22 and 33 degree locations were presented with the same timing, but using fiber optics to direct stimuli near the eye. During the presentation of the stimuli the subjects alternated their attention between a single left and right location while maintaining central gaze. BOLD response to the stimuli at the attended and unattended locations was evaluated. All subjects showed a response in visual areas V1, V2/VP, and MT+, in both attended and unattended conditions. A number of parietal locations also responded well to the visual stimuli. At all of these locations subjects showed a significant modulation of activation with sustained attention. The magnitude of the modulation was similar for the near and far periphery, but varied by visual region; MT+ showed the greatest modulation.