Short wavelength sensitive cone increments on dynamic backgrounds

The purpose of this experiment was to compare S‐cone mediated human psychophysical thresholds with in vivo recordings from S‐cone excited macaque retinal ganglion cells [+S − (L + M)] in the presence of luminance‐modulated and chromaticity‐modulated long‐wavelength backgrounds. For psychophysics, increment thresholds were measured for 2°, 3 ms test pulses on a 12°, 2 Hz sine wave background. Test pulse chromaticity was 460 nm. The background was formed by 561 and 645 nm LEDs, either modulated in phase or in counterphase. The time‐averaged retinal illuminance was 2500 td, with chromaticity metameric to 588 nm. For electrophysiology, response amplitude to a 9.76 Hz test sine wave was measured on a 0.61 Hz sine wave background, using a 4.7° field. The test was an S‐cone isolating (tritan) stimulus. The background was formed by 553 and 636 nm equiluminant LEDs, either modulated in phase or in counterphase. The time‐averaged retinal illuminance and chromaticity were 2000 td and 595 nm (for a human observer). The psychophysical data revealed that both chromatic and luminance background modulation resulted in threshold elevations. The electrophysiology revealed that the S − (L + M) ganglion cells were modulated by the luminance‐modulated background, but not by the chromatic‐modulated background. © 2000 John Wiley & Sons, Inc. Col Res Appl, 26, S150–S156, 2001