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BIOLOGICAL SCIENCES / NEUROSCIENCE
Geniculocortical relay of blue-off signals in the primate visual system
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*National Vision Research Institute of Australia, Department of Optometry and Vision Sciences, University of Melbourne, Corner Keppel and Cardigan Streets, Carlton VIC 3053, Australia; and Discipline of Anatomy and Histology, School of Biomedical Sciences and Bosch Institute, University of Sydney, Sydney NSW 2006, Australia
Edited by Jon H. Kaas, Vanderbilt University, Nashville, TN, and approved October 30, 2006 (received for review August 12, 2006)
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.
color vision | short-wavelength-sensitive cones | blue cones | koniocellular pathway | lateral geniculate nucleus
The authors declare no conflict of interest.
This article is a PNAS direct submission.
To whom correspondence should be sent at the * address. E-mail: prmartin{at}unimelb.edu.au
© 2006 by The National Academy of Sciences of the USA
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