In their pursuit to better elucidate the functional circuits that comprise the neocortex , Assistant Professor of Neurobiology Hillel Adesnik and his team made a possibly paradigm shifting discovery. They recently published their findings in Nature Neuroscience.
A major focus of neurobiology research is to understand the organization of the neocortex: the outer layers of the cerebral hemispheres that underlie that most complex mental capabilities. The neocortex is comprised of 6 layers of cells that are remarkably diverse in form and function and are highly interconnected to form complex networks with both local and long-range targets. To better understand the relationship between the layers of neocortical neurons, the Adesnik lab used optogenetics to photo-manipulate the main input layer of the primary sensory cortex: layer 4 (L4). Contrary to all existing models of neocortical organization, they discovered that L4 exerts a powerful, disynaptic inhibitory action onto the main output layer: layer 5. The functional consequence of this inhibition is a reduction in noise and a sharpening of sensory representations. Hence, neurons within layer 4 may act as a key node through which higher cortical areas dynamically sharpen stimulus representations according to behavioral demands.