August 2012
Volume 12, Issue 9
Free
Vision Sciences Society Annual Meeting Abstract  |   August 2012
Eccentricity representation of visual stimulation, attention, and saccades in human superior colliculus
Author Affiliations
  • Sucharit Katyal
    Psychology, University of Texas at Austin\nImaging Research Center, University of Texas at Austin
  • Clint Greene
    Neurobiology, University of Texas at Austin\nImaging Research Center, University of Texas at Austin
  • Evan Luther
    Neurobiology, University of Texas at Austin\nImaging Research Center, University of Texas at Austin
  • David Ress
    Neurobiology, University of Texas at Austin\nPsychology, University of Texas at Austin
Journal of Vision August 2012, Vol.12, 129. doi:10.1167/12.9.129
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      Sucharit Katyal, Clint Greene, Evan Luther, David Ress; Eccentricity representation of visual stimulation, attention, and saccades in human superior colliculus. Journal of Vision 2012;12(9):129. doi: 10.1167/12.9.129.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract
 

We previously demonstrated using high-resolution fMRI that polar angle topographic representations of visual stimulation and attention in human SC overlap and are similar to macaque. Here we measure the representation of eccentricity for visual stimulation, attention and saccades. Methods: Visual stimulation was measured using a phase-encoded protocol. Subjects fixate at one edge of the display while an expanding wedge of moving dots (50° polar angle, 2°/s moving dots) was presented for a single hemifield at 6 equally spaced eccentricities between 5—30°. Wedges were divided into four virtual sectors and subjects performed a speed-discrimination task. Visual attention was measured with subjects performing the speed-discrimination task alternately within inner and outer sectors of moving dots (2—5.5° and 10—14°) that were continually present. Experiments with larger field-of-view and four eccentricity ranges are in progress. Saccadic eye movements were measured with blocks of saccades vs. fixation. In saccade blocks, subjects followed a white dot whose position alternated between two sectors in the left and right hemifields (0.6 sec/saccade). In fixation blocks, subjects fixated on a stationary dot within one of the two sectors while performing a dot color-counting task. Distance between the two sectors was varied across fMRI runs to get 3 saccade eccentricity ranges: 7—10°, 15—20° and 26—31° with 6 runs per condition. For all experiments, high-resolution fMRI (1.2 mm voxels, 3-shot spiral) was acquired (3 sec/volume) in 8 slices covering SC (24-sec period, 9 cycles/run). Results: Visual stimulation was represented in the contralateral colliculus with a clear rostral-to-caudal progression with increasing eccentricities. Attention and saccade representation also had a rostro-caudal progression, but saccade representations did not show precise agreement with stimulation. Conclusion: Visual stimulation, attention and saccadic eye movements’ representations of eccentricity in human SC all follow a rostro-caudal progression similar to those observed in macaques.

 

Meeting abstract presented at VSS 2012

 
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