Stimulus-response diversity in local neuronal populations of the cerebral cortex.

In cortex, neighboring 0.05 mm minicolumns have distinctly different receptive fields (RFs). Within minicolumns, neighboring cells have very similar RFs, but differ prominently in their stimulus-evoked temporal behaviors. This is reproduced in a cortical model that has strong inhibition and semi-random lateral connections among cells with similar RFs. Within modeled minicolumns, non-linear dynamics amplify small differences in cells' lateral inputs into large differences in temporal behaviors. Cells' stimulus-evoked behaviors, though complex, are surprisingly orderly, in that (1) time courses of cells' responses are very stimulus-specific and (2) in the presence of a stimulus, activities of some cells fluctuate coherently, and the patterns of coherence are also stimulus-specific. Thus the model, like real cortex, represents stimulus information in the overall strengths and temporal patterns of cells' responses and in patterns of temporal coherence among cells.