A new code for contrast in the primate visual pathway.
We characterize a hitherto undocumented type of neuron present in the regions bordering the principal layers of the macaque lateral geniculate nucleus. Neurons of this type were distinguished by a high and unusually regular maintained discharge that was suppressed by spatiotemporal modulation of luminance or chromaticity within the receptive field. The response to any effective stimulus was a reduction in discharge, reminiscent of the "suppressed-by-contrast" cells of the cat retina. To a counterphase-modulated grating, the response was a phase-insensitive suppression modulated at twice the stimulus frequency, implying a receptive field comprised of multiple mechanisms that generate rectifying responses. This distinctive nonlinearity makes the neurons well suited to computing a measure of contrast energy; such a signal might be important in regulating sensitivity early in visual cortex.
Tailby
Chris
C
Center for Neural Science, New York University, New York, New York 10003, USA. ctailby@unimelb.edu.au
Solomon
Samuel G
SG
Dhruv
Neel T
NT
Majaj
Najib J
NJ
Sokol
Sach H
SH
Lennie
Peter
P
D000818:Animals; D015350:Contrast Sensitivity / Q000502:physiology*; D008252:Macaca fascicularis; D008297:Male; D010775:Photic Stimulation / Q000379:methods*; D014794:Visual Fields / Q000502:physiology; D014795:Visual Pathways / Q000502:physiology*