Mechanisms subserving temporal modulation sensitivity in silent-cone substitution.
Temporal contrast sensitivity data were collected with sine-wave-modulated lights for achromatic, chromatic, and silent-cone-substitution stimuli. Achromatic (556- and 642-nm lights in phase) and chromatic (556- and 642-nm lights in counterphase) modulation sensitivities were measured at a constant time-average retinal illuminance of 1256 trolands (Td) and chromaticity of 595 nm. These data were considered to represent isolated temporal responses of luminance and red-green chromatic channels, respectively. Silent cone substitution was achieved with counterphase modulation of the 556- and the 642-nm lights and by suitable adjustment of the modulations or the radiances of the two lights. (1) The peak modulation depth of the 642-nm light was reduced to silence the long-wavelength-sensitive (LWS) cone, and the peak modulation depth of the 556-nm light was reduced to silence the middle-wavelength-sensitive (MWS) cone. These protocols maintained the time-average retinal illuminance and chromaticity as for the control conditions. (2) The luminance of the 642-nm light was decreased to silence the LWS cone and was increased to silence the MWS cone. In this procedure the time-average retinal illuminance and chromaticity differ for the silenced-LWS-cone (1047 Td and 589.5 nm) and the silenced-MWS-cone (4358 Td and 622 nm) conditions. The response modulation of the achromatic and the chromatic channels was calculated for the silent-substitution conditions. The chromatic channel is more sensitive at low frequencies, with a transition to greater achromatic channel sensitivity near 13 Hz for the silenced-LWS-cone condition and near 6 Hz for the silenced-MWS-cone condition.(ABSTRACT TRUNCATED AT 250 WORDS)
Smith
V C
VC
Visual Sciences Center, University of Chicago, Illinois 60637.
Pokorny
J
J
Davis
M
M
Yeh
T
T
D000328:Adult; D003118:Color Perception / Q000502:physiology; D015350:Contrast Sensitivity / Q000502:physiology*; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D008433:Mathematics; D008875:Middle Aged; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D014795:Visual Pathways