Role of Feed-Forward Inhibition in Neocortical Information Processing: Implications for Neurological Disorders

A major well-documented feature of cortical functional organization is the presence of prominent broadly tuned feed-forward inhibition in the input layer 4, in which local layer 4 inhibitory cells receive direct thalamocortical input and in turn suppress responses of neighboring layer 4 excitatory cells to their thalamocortical drive, thereby sharpening their receptive field properties. Here we review the evidence that the presence of broadly tuned feed-forward inhibition in layer 4 turns local layer 4 domains into functional analogs of Radial Basis Function networks, enabling layer 4 to contribute importantly to sensory information processing as a pluripotent function linearizer: i.e., it performs such a transform of afferent inputs to a cortical column that makes possible for neurons in the upper layers of the column to learn and perform their complex functions using primarily linear operations.