Pulse-duration threshold functions obtained at the MWS/LWS cone antagonistic locus.

Pulse-duration threshold functions were determined for spectral increments in the region of the Sloan notch (580 nm) as well as for 440 and 640 nm and white increments flashed on a spatially coincident white background. While increments of 440 and 640 nm elicited traditional pulse-duration functions with decreasing thresholds as the duration increased, functions obtained with 580 nm and white increments manifested a minima at about 50 ms. These data support the notion that stimuli in the region of Sloan's notch can be detected by an achromatic mechanism that may integrate sub-threshold ON and OFF responses, thereby maximizing detection sensitivity.