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Ben Harvey, Serge Dumoulin, Alessio Fracasso; A fronto-parietal network of visual event duration-tuned topographic maps. Journal of Vision 2018;18(10):962. doi: https://doi.org/10.1167/18.10.962.
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Introduction: Precise quantification of sub-second visual event timing is vital to understanding and interacting with our complex, dynamic environment, for example following temporal patterns in sports and traffic. However, despite the central role of timing in perception and action planning, it remains unclear how the brain encodes and represents visual event timing. Converging evidence from psychophysical adaptation, neurophysiology of motor planning and computational modelling suggests the presence of tuned neural responses to specific event durations, together with responses that monotonically increase or decrease with duration. We therefore hypothesized that neural populations in the human brain may exhibit tuned responses to visual event timing, while other brain areas may monotonically change their response amplitude with duration. Methods: 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 summarized the fMRI responses to these events using neural models tuned to duration and period, following a population receptive field (pRF) modeling approach. Results: Models tuned to event duration captured fMRI responses well in four bilateral frontal and parietal areas. Within these areas, duration preferences progressed gradually across the cortical surface, forming topographic maps of event timing preferences. These timing maps largely overlap with a network of numerosity maps that we recently described. Furthermore, area MT monotonically decreases its responses amplitude with increasing event duration, a likely intermediate stage in computing duration-tuned responses. Conclusion: Neural populations tuned to specific event timings, organized into topographic maps, suggest the neural representation of visual event timing is similar to that of both sensory spaces and other quantities, such as numerosity and object size. Their superior parietal and frontal locations suggest a role in multisensory integration and sensory-motor transformations.
Meeting abstract presented at VSS 2018
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