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Chengwen Liu, Sheng He, Peng Zhang; Attentional modulation of layer-specific BOLD signals in human early visual cortex. Journal of Vision 2017;17(10):521. doi: https://doi.org/10.1167/17.10.521.
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Human early visual cortex consists of six layers, with distinct roles in feedforward, lateral, feedback connections. The nature of attentional modulation at different cortical layers of visual cortex remains unclear. With submillimeter-resolution fMRI at 7 Tesla, we investigated the top-down attentional modulation of layer-specific BOLD signals in human early visual cortex . Stimuli were full-field checkerboard patterns counterphase flickering at 7.5 Hz. In the attend-checkerboard condition, subjects were instructed to detect the occasional spatial frequency change of the checkerboard. In the attend-fixation condition, they performed a demanding central fixation task and the checkerboard stimulus was task-irrelevant. The checkerboard pattern was presented at 50% contrast in experiment 1, and 5% contrast in experiment 2. FMRI Data were acquired with a single slice high-resolution passband b-SSFP sequence (0.64*0.64 mm in-plane resolution, 3mm slice thickness, placed perpendicular to the calcarine sulcus). Experiment 1 showed that in the attend-fixation condition, the stimulus-driven response to the high contrast checkerboard peaked in the mid-layers of the gray matter, while attending to the checkerboard generated the strongest attentional modulation in the superficial layers, i.e., voxels close to the gray matter surface. In experiment 2, the low contrast checkerboard stimulus, when not attended, produced minimal activities in the visual cortex; but again the response in the attended condition was strongest in the superficial voxels. The response from V1 to V3 showed similar patterns: stimulus-driven activities peaked in the middle layers, while the modulation of top-down spatial attention was strongest in the superficial layers.
Meeting abstract presented at VSS 2017
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