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"The visual cortex as a cognitive blackboard"

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Most theories hold that early visual cortex is responsible for the local analysis of simple features while cognitive processes take place in higher areas of the parietal and frontal cortex. However, these theories are not undisputed because there are findings that implicate early visual cortex in visual cognition – in tasks where subjects reason about what they see. Are these cognitive effects in early visual cortex an epiphenomenon or are they functionally relevant for these mental operations?

I will discuss new evidence supporting the hypothesis that the modulation of activity in early visual areas has a causal role in cognition. The modulatory influences allow the early visual cortex to act as a multiscale cognitive blackboard for read and write operations by higher visual areas, which can thereby efficiently exchange information. This blackboard architecture explains how the activity of neurons in the early visual cortex contributes to scene segmentation and working memory, and relates to the subject’s inferences about the visual world.

I will illustrate these ideas with a contour grouping task and a working memory task. In the contour-grouping task, subjects see a number of curves and it is their task to mentally trace one curve (target curve) and to ignore the other curves (distractor curves). We recorded neuronal activity in the different layers of V1 of monkeys during this task and we also recorded neuronal activity in area V3 of a human patient, implanted with electrodes for the treatment of epilepsy. When the monkey or human subjects mentally trace a target curve, the representation of this curve is enhanced in early visual cortex. In the monkeys, we observed a characteristic profile of top-down inputs in the superficial layers and layer 5 causing an increase in the firing rates in feedback recipient layers. We also observed working memory signals in area V1. These results provide new insights in the role of early visual cortex as a cognitive blackboard that supports the implementation of mental programs.

This talk is part of the Adrian Seminars in Neuroscience series.

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