Segregation of chromatic and luminance signals using a novel grating stimulus.

Segregation of chromatic and luminance signals in afferent pathways are investigated with a grating stimulus containing luminance and chromatic components of different spatial frequencies. Ganglion cell recordings were obtained from the retinae of macaques (Macaca fascicularis). Cell responses to the 'compound' gratings were compared to responses to standard chromatic and luminance gratings. Parvocellular (PC) pathway cell responses to compound and chromatic gratings were very similar, as were magnocellular (MC) cell responses to compound and luminance gratings. This was the case over a broad range of spatial and temporal frequencies and contrasts. In psychophysical experiments with human observers, discrimination between grating types was possible close to detection threshold. These results are consistent with chromatic and luminance structure in complex patterns being strictly localized in different afferent pathways. This novel stimulus may prove useful in identifying afferent inputs to cortical neurons.