Black’’ responses dominate macaque primary visual cortex V1

Achromatic visual information is transferred from the retina to the brain through two parallel channels: ON-center cells carry ‘white ’ information and OFF-center cells ‘black ’ information (Nelson et al., 1978; Schiller, 1982; Schiller et al., 1986). Responses of ON and OFF retinal and thalamic neurons are approximately equal in magnitude (Krüger and Fischer, 1975; Kremers et al., 1993), but psychophysical studies have shown that humans detect light decrements (black) bette