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Ben Harvey, Serge Dumoulin, Alessio Fracasso, Jacob Paul; A network of topographic maps in human association cortex hierarchically transforms visual timing-selective responses. Journal of Vision 2020;20(11):538. doi: https://doi.org/10.1167/jov.20.11.538.
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Accurately timing sensory events is crucial when interacting with our dynamic world. This allows complex human behaviors that require timing-dependent multisensory integration and action planning. Such behaviors include perception and performance of speech, music, driving and many sports. How are responses to visual event timing processed for multisensory integration and action planning? We hypothesized that human cortical neural populations may exhibit tuned responses to visual event timing in a network of topographically organized areas.
We acquired ultra-high field (7T) fMRI data while showing subjects visual events (a circle appearing and disappearing) that gradually varied the time between circle appearance and disappearance (duration) and/or the time between consecutive circle appearances (period, i.e. 1/frequency). We analyzed these responses with neural population response models selective for event duration and period, following behavioral and computational results, and comparisons to alternative models.
We found nine bilateral timing maps, partially left-lateralized and widely spread from occipital visual areas through parietal multisensory areas to frontal action planning areas. Each map showed topographically organized, tuned responses to duration and period, mirroring the organization of sensory cortices and other quantity (e.g. numerosity) processing networks. Duration and period representations were closely linked. As in sensory cortical maps, response precision varied systematically with timing preferences and timing selectivity systematically varied between maps. Progressing from posterior to anterior maps, responses to multiple events were increasingly integrated, response selectivity narrowed, and responses focused increasingly on the middle of the presented timing range.
These timing maps largely overlap with the numerosity map network, suggesting close links to cortical representation of other quantities. Their locations suggest roles in visual motion processing, multisensory integration and sensory-motor transformations. In both visual timing map and visual field map networks, selective responses and topographic map organization may facilitate hierarchical transformations by allowing neural populations to interact over minimal distances.
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