The role of the superficial cortical layers in whisker-based shape discrimination

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 DESCRIPTION (provided by applicant): The cerebral cortex is a structure in the brain that is important for sensory processing and decision making. Although different regions of cortex are specialized for different behavioral functions, all regions share the same basic anatomical structure - most strikingly, its six anatomical layers. The layers differ in the types of neurons they contain and the way in which they connect to other parts of the brain. This suggests that the different layers may have different functions, either in the computations they perform or the behaviors they produce. In particular, we hypothesize that the most superficial layers of cortex are critical for integrating information across different cortical regions. This hypothesis is base on the observation that the superficial layers are strongly interconnected and send long-distance projections to connect sensory, associative, and higher-order regions. If this hypothesis is true, then the superficial layers would be especially important for behaviors that require integrating information, for instance, across different parts of the sensory world or across different parts of the body. To test this hypothesis, we are using as a model the mouse whisker system. Mice rely on their whiskers to investigate the world around them; their whisker system uses specialized motor circuits to generate nuanced and complex whisker motions in order to make fine discriminations about objects in their environment. Though the peripheral mechanics differ, this is broadly similar to the way we use our fingertips to explore the world around us. In both systems, the somatosensory cortex faces the problem of combining information from each sensory receptor, be it whisker or finger, into an overall perception of object form and identity. We thus consider this behavior to be an excellent one to test our hypothesis that the superficial layers integrate information. In particular, we will test that activity in the superficial layers i necessary for mice to discriminate shapes, and we will record that activity to determine how the brain represents objects and generates appropriate behavioral responses to them.