THE EFFECT OF SPATIAL-FREQUENCY AND CONTRAST ON THE LATENCY IN THE VISUAL EVOKED-POTENTIAL

The latency in the visual evoked potential was measured at spatial frequencies of 2-12 c/deg in 10 subjects. The contrast levels of the sinusoidal grating patterns were set at 1.5, 1.75, 2.0, 2.25, 2.5, 2.75 and 3.0 log units above each subject's contrast sensitivity threshold. Two factors were shown to influence the latency: suprathreshold contrast and, to a lesser extent, spatial frequency. The visual evoked potential latencies at contrast sensitivity threshold were extrapolated. These threshold latencies showed considerable variation with spatial frequency and between subjects. Therefore, the visual evoked potential latency cannot be considered a useful tool for estimating the contrast sensitivity function.