Neuronal connection of the cortex and reconstruction of the visual space.

The distributions of retrograde labeled cells in fields 17 and 18 and the fields 17/18 transitional zone were studied in both hemispheres of cats after microiontophoretic administration of horseradish peroxidase into individual cortical columns in fields 17, 18, 19, and 21a. The clustered organization of the internal connections of the cortical fields, the asymmetrical locations of labeled callosal cells relative to the injected columns, and the defined distribution of labeled cells in layers A of the lateral geniculate body suggested that eye-specific neuronal connections support "binding" of the visual hemifields separately for each eye. Application of marker to columns in fields 19 or 21a demonstrated disparate inputs from fields 17 and 18 and the fields 17/18 transitional zone. It is suggested that these connections may support the extraction of loci and stereoscopic boundaries located in the central sectors of the visual space.