Luminance coding of briefly presented stimuli in area 17 of the rhesus monkey.

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Abstract
Single cells in area 17 of the alert rhesus monkey were classified according to their sensitivity to variations in stimulus orientation, color and direction of movement. The sensitivity of the cells to stimulus luminance was tested using moving bars and large stationary spots presented for 500 ms. The luminance of the stimulus was varied over trials; background luminance was constant. Short stimulus durations and long intertrial intervals were chosen to minimize changes in light adaptation, and thus compare responses to briefly presented stimuli of different luminances at a constant mesopic adaptation level (0.15 ft-L [lumen]). Moving bars were chosen so as to be of optimal orientation for orientation-specific cells. Orientation-specific cells differ from cells without orientation specificity in the range of stimulus luminances over which they respond differentially. Orientation-specific cells show response saturation at luminances 2-10 times the background luminance. Cells without orientation specificity respond differentially over a larger luminance range; some of these cells do not show response saturation within the range tested. Apparently, under conditions of constant light adaptation, the luminance of a brief stimulus is more reliably coded by cells without orientation specificity, particularly at higher stimulus luminances.