The Nature and Plasticity of Sensory Processing within Adult Rat Barrel Cortex

Abstract

The central tenet of the columnar hypothesis for sensory cortical organization (Mountcastle, 1957) is locus specificity; the idea of single columnar neuronal groups targeted by unimodal information from separate peripheral loci. Mountcastle conceived of the column as a single processing module, and implied that somatosensory cortex is constructed of an array of independent modules, each processing “labeled line” sensory information with uniform latency. The thinking behind the hypothesis is often a common starting point for theories of differentiation or modification of cortical neuronal groups in relation to learning (Edelman, 1978, 1987; Eccles, 1984; Changeux et al., 1984; Von der Malsberg, 1987). Processing within the column itself, or analogous neuronal groups has often relied on a black box approach to the neuronal group, using such devices as “hidden layers” and “back propagation” (Rumelhart et al., 1986; Zipser and Andersen, 1988). This maneuver has largely been required in the dearth of useful information on how spatiotemporal processing proceeds within sensory cortex (Douglas and Martin, 1990).