Tangential segregation of simple and complex cells in the visual cortex and their connections. A universal neocortical module.

In the visual cortex of the guinea pig brain, the primary convergence zones for afferents correspond to basal modules--columns which are about 200 microm in diameter-and are separated by secondary convergence zones. The former are characterized by their concentrations of neurons with simple receptive fields and afferent inhibitory cells, and have a different organization of local interneuronal connections as compared with secondary convergence zones, which have an increased proportion of inhibitory influences, addressed excitatory inputs, and more selectivity in their cellular reactions. The basal modules have parameters similar to those of higher mammals; secondary convergence zones are smaller in rodents, and have simpler organization.