The chromatic input to cells of the magnocellular pathway of primates.
Parasol ganglion cells of the magnocellular (MC) pathway form the physiological substrate of a luminance channel underlying photometric tasks, but they also respond weakly to red-green chromatic modulation. This may take the form of a first-harmonic (1F) response to chromatic modulation at low temporal frequencies, and/or a second-harmonic (2F) response that is more marked at higher frequencies. It is shown here that both these responses originate from a receptive field component that is intermediate in size between center and surround, i.e., a discrete, chromatic receptive field is superimposed upon an achromatic center-surround structure. Its size is similar to the receptive field (center plus surround) of midget, parvocellular cells from the same retinal eccentricity. A 2F MC cell chromatic response component is shown to be present under cone silent substitution conditions, when only the middle- (M) or long-wavelength (L) cone is modulated. This and other features suggest it is a rectified response to a chromatic signal rather than a consequence of non-linear summation of M- and L-cone signals. A scheme is presented which could give rise to such responses. It is suggested that this chromatic input to MC cells can enhance motion signals to red-green borders close to equiluminance.
Lee
Barry B
BB
SUNY College of Optometry, New York, NY 10036, USA. blee@sunyopt.edu
Sun
Hao
H
D000818:Animals; D001288:Attention / Q000502:physiology*; D055253:Color Vision / Q000502:physiology*; D008252:Macaca fascicularis; D010775:Photic Stimulation / Q000379:methods; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology; D012165:Retinal Ganglion Cells / Q000502:physiology*; D012399:Rotation; D013028:Space Perception / Q000502:physiology; D013997:Time Factors; D014794:Visual Fields; D014795:Visual Pathways / Q000166:cytology / Q000502:physiology*