| Presentation Number: |
649.3 |
| Abstract Title: |
Modulation of visual responses in human striate, extrastriate, and parietal cortex. |
| Authors: |
Merriam, E. P.*1;
Genovese, C. R.;
Colby, C. L.1
1Dept. of Neurosci., Univ. of Pittsburgh, Pittsburgh, PA
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| Primary Theme and Topics |
Sensory Systems
- Vision
-- Visual cortex: Perception and action
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| Session: |
649. Perception and Action
Poster |
| Presentation Time: |
Tuesday October 26, 2004 10:00 AM-11:00 AM |
| Location: |
Convention Center Exhibit Hall, Poster Board BB4 |
| Keywords: |
PARIETAL CORTEX, SACCADE, ATTENTION, MODULATION
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We used fMRI to test the hypothesis that visual response properties in human cortex are modulated by performance of saccades. We used an m-sequence to probe the temporal and spatial characteristics of the fMRI response to contrast-modulated visual stimuli. On a given trial, subjects either maintained fixation or made a saccade just after stimulus offset. Stimuli were located 8-10 deg from the fovea. The size and direction of the saccade were selected so as to bring the location of the preceding stimulus into the opposite hemifield. To account for retinal effects of the saccade itself, subjects were scanned on a control condition in which they made saccades in the absence of visual stimuli.
Saccades modulated two aspects of the visual response. First, saccades enhanced the strength of contralateral visual activity. This effect was observed in all cortical areas studied. Second, we observed activation in the hemisphere that was initially ipsilateral to the stimulus. This ipsilateral activation was not present in the fixation trials, and cannot be attributed to the eye movement or to direct visual stimulation. This effect is consistent with updating a memory trace of the stimulus in conjunction with the eye movement.
In monkeys, updating activity is most prevalent in parietal cortex, and is progressively less prevalent at earlier stages of visual processing. We found a similar pattern in humans. The normalized updating signal was largest in parietal cortex and was smallest in striate cortex, indicating a parallel with the physiological data. These results demonstrate that saccades have a profound impact on visual processing throughout human visual cortex.
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| Supported by NSF-IGERT DGE-9987588 and NIH NS047493 |
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| Sample Citation: |
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[Authors]. [Abstract Title]. Program No. XXX.XX. 2004 Neuroscience Meeting Planner. San Diego, CA: Society for Neuroscience, 2004. Online.
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| Copyright © 2004-2010 Society for Neuroscience; all rights reserved. Permission to republish any abstract or part of any abstract in any form must be obtained in writing by SfN office prior to publication.
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