Geniculocortical relay of blue-off signals in the primate visual system.
A fundamental dichotomy in the subcortical visual system exists between on- and off-type neurons, which respectively signal increases and decreases of light intensity in the visual environment. In primates, signals for red-green color vision are carried by both on- and off-type neurons in the parvocellular division of the subcortical pathway. It is thought that on-type signals for blue-yellow color vision are carried by cells in a distinct, diffusely projecting (koniocellular) pathway, but the pathway taken by blue-off signals is not known. Here, we measured blue-off responses in the subcortical visual pathway of marmoset monkeys. We found that the cells exhibiting blue-off responses are largely segregated to the koniocellular pathway. The blue-off cells show relatively large receptive fields, sluggish responses to maintained contrast, little sign of an inhibitory receptive-field surround mechanism, and negligible functional input from an intrinsic (melanopsin-based) phototransductive mechanism. These properties are consistent with input from koniocellular or "W-like" ganglion cells in the retina and suggest that blue-off cells, as previously shown for blue-on cells, could contribute to cortical mechanisms for visual perception via the koniocellular pathway.
Szmajda
Brett A
BA
National Vision Research Institute of Australia, University of Melbourne, Carlton VIC 3053, Australia.
Buzás
Péter
P
Fitzgibbon
Thomas
T
Martin
Paul R
PR
D000818:Animals; D002144:Callithrix / Q000235:genetics / Q000502:physiology*; D003118:Color Perception / Q000502:physiology*; D005260:Female; D008297:Male; D009475:Neurons, Afferent / Q000166:cytology / Q000502:physiology; D010775:Photic Stimulation; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000502:physiology; D014795:Visual Pathways / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*