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Brian J. White, Laurent Itti, Douglas P. Munoz; Visual coding in the superior colliculus during unconstrained viewing of natural dynamic video. Journal of Vision 2014;14(10):1447. doi: 10.1167/14.10.1447.
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© ARVO (1962-2015); The Authors (2016-present)
The superior colliculus (SC) is a multilayered midbrain structure with visual representations in the superficial-layers (SCs), and sensorimotor representations linked to the control of eye movements/attention in the intermediate-layers (SCi). Although we have extensive knowledge of the SC using simple stimuli, we know little about how the SC behaves during active-vision of complex natural stimuli. We recorded single-units in the monkey SC during unconstrained viewing of natural dynamic video. We used a computational model to predict visual saliency at any retinal location, any point in time. We parsed fixations into tertiles according to the averaged model-predicted saliency value (low, medium, high) in the response field (RF) around the time of fixation (50-400ms post-fixation). The results showed a systematic increase in post-fixation discharge with increasing saliency. We then examined a subset of the total fixations based on the direction of the next saccade (into vs. opposite the RF), under the assumption that saccade direction coarsely indicates the top-down goal of the animal ("value" of the goal-directed stimulus). SCs neurons showed the same enhanced response for greater saliency irrespective of next saccade direction, whereas SCi neurons only showed an enhanced response for greater saliency when the stimulus that evoked it was the goal of the next saccade (was of interest/value). This implies that saliency is controlled closer to the output of the saccade circuit, where priority (combined representation of saliency and relevancy) is presumably signaled and the saccade command is generated. The results support functionally distinct roles of SCs and SCi, whereby the former fit the role of a visual saliency map, and the latter a priority map.
Meeting abstract presented at VSS 2014
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