Feedback of Peripheral Visual Information to Foveal Cortex

Massachusetts Institute Of Technology, Cambridge MA

Investigators

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Abstract

Project Summary: We humans are extraordinarily visual organisms, indeed a third of our cerebral cortex is devoted to processing visual information. The main starting point for much of this processing is a large region at the back of the brain called primary visual cortex, which holds a maplike representation of the visual world. This region connects to at least thirty other regions of the brain, each of which processes a different kind of visual information. Although most research focuses on the forward processing of visual information from primary visual cortex up to these higher stages of the visual brain, in fact it has been known for decades that there are at least as many connections that go in the other direction, from high visual areas backward down to primary visual cortex. Yet, the role of these backward connections in visual perception is not well understood. This proposal asks what those backward visual connections do, by investigating a surprising new phenomenon reported very recently by the PI's lab. In this new phenomenon, brain imaging (specifically, functional magnetic resonance imaging, or fMRI) was used to show that high-level information about the shape of an object represented presented in the peripheral visual field is present the center of the maplike representation in primary visual cortex. This finding is surprising because this information is in the wrong part of the visual map, so this information must be coming from higher level parts of the visual system, via the backward connections. This proposal uses fMRI, as well as behavioral methods and a method called transcranial magnetic stimulation (TMS) that allows us to disrupt this maplike representation, to ask why this feedback representation is found in visual cortex, whether it plays a causal role in visual perception, and exactly where it is within the maplike part of visual cortex.