Laminar specificity of extrinsic cortical connections studied in coculture preparations.

The formation of specific neural connections in the cerebral cortex was studied using organotypic coculture preparations composed of subcortical and cortical regions. Morphological and electrophysiological analysis indicated that several cortical efferent and afferent connections, such as the corticothalamic, thalamocortical, corticocortical, and corticotectal connections, were established in the cocultures with essentially the same laminar specificity as that found in the adult cerebral cortex, but without specificity of sensory modality. This suggests the existence of a cell-cell recognition system between cortical or subcortical neurons and their final targets. This interaction produces lamina-specific connections, but is probably insufficient for the formation of the modality-specific connections.