SPATIAL-RESOLUTION AND CONTRAST SENSITIVITY OF SINGLE NEURONS IN AREA-19 OF SPLIT-CHIASM CATS - A COMPARISON WITH PRIMARY VISUAL-CORTEX

Electrophysiological recordings were carried out in the callosal recip ient zone of area 19 in normal and split-chiasm cats and, for comparis on purposes, at the border of areas 17 and 18 of split-chiasm cats. Th e influences of retinothalamic and callosal inputs on a single cortica l neurons were thereby evaluated. Extracellular recordings of single c ells were made in anaesthetized and paralysed cats in the zone represe nting the central visual field. Receptive field properties were assess ed using sine wave gratings drifting in optimal directions. Results sh owed that in area 19 and areas 17/18 one-third of the cells were binoc ularly driven after section of the optic chiasm. In area 19, the spati al resolution and contrast sensitivity of cells driven via the dominan t eye were similar in the normal and split-chiasm groups. In areas 17/ 18 and area 19 of split-chiasm cats, binocular cells showed significan t interocular matching of their receptive field properties (spatial re solution and contrast threshold), although small differences were obse rved. These small interocular differences were related to the cell's o cular dominance rather than to the signal transmission route (thalamic or callosal).