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Chih-Yang Chen, Ziad M. Hafed; Peri-microsaccadic modulation of visual activity in the primate superior colliculus: dependence on movement direction and neuronal cell type. Journal of Vision 2013;13(9):1204. doi: 10.1167/13.9.1204.
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© ARVO (1962-2015); The Authors (2016-present)
Perceptual thresholds are elevated around the time of microsaccades. A neural correlate for such ‘microsaccadic suppression’ has recently been described in superior colliculus (SC) (Hafed & Krauzlis, 2010), but the dependence of this ‘suppression’ on visual location, microsaccade direction, or neuronal cell type is currently unknown. Here we tested for such dependence, to fully understand how microsaccades affect perceptual performance. We recorded SC activity from one monkey fixating a white spot over a gray background. Inside a neuron’s response field (RF), we displayed a square (1-5 deg) containing a vertical sine-wave grating (2.2 cpd) for ~250 ms. We measured peak neuronal activity 50-150 ms after grating onset and divided trials into three groups: 1) the grating appeared without microsaccade <300 ms from its onset; 2) the same grating appeared <100 ms before microsaccades; 3) the grating appeared <100 ms after microsaccades. We recorded ‘visual-motor’ and ‘visual-only’ SC neurons. Across 49 neurons (29 visual-motor and 20 visual-only), most (~94%) exhibited peri-microsaccadic modulation of visual activity. The most common observation was strong suppression for stimuli appearing right after microsaccades (~90% of visual-motor neurons and ~65% of visual-only neurons). For stimuli appearing before microsaccades, the neuronal modulations depended both on cell type and movement direction. Specifically, for microsaccades away from the RF location, most visual-motor neurons (~62%) were suppressed; for microsaccades toward the RF, ~38% showed suppression and ~24% enhancement. For visual-only neurons, only ~5% showed suppression for stimuli before microsaccades and ~70% showed enhancement, irrespective of microsaccade direction. Thus, peri-microsaccadic modulation of SC visual activity is pervasive, with specific differences between neuronal cell types. Besides providing a more complete characterization of peri-microsaccadic changes in vision, our work reveals a possible neural basis for recent observations that microsaccade direction has a strong, eccentricity-dependent influence on perceptual performance (Hafed, Society for Neuroscience Meeting, 2012).
Meeting abstract presented at VSS 2013
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