The relationship between the Broca-Sulzer effect and visually evoked potentials (VEPs) was examined with two subjects. In the psychophysical experiment, a flash of disc subtending 52' in visual angle and of one of the 11 durations ranging from 0 (no stimulus) to 1 000 ms was presented by means of a Maxwellian view system. The luminance levels were at 312, 987, and 3 120 cd/m2. Brightness judgments were made with the method of magnitude estimation. In the VEP experiment, 300-summed VEPs were obtained from 01 in the 10-20 system at six durations ranging from 0 to 500 ms and at 312 and 3 120 cd/m2. As to the VEP components (P1, N1, P2, N2), two indices of the areas QP1N1P2 and QNiP2N2 were measured with a planimeter and were used for the analysis. The results indicated the positive correlation between the apparent brightness enhancement and the VEP responses.

Click and [iglu were presented in pairs with varying stimulus onset asynchronies (SOAs) and the subjects were asked to respond to the click onset. SRTs and EPs were obtained for two levels of click intensity and were plotted as a function of SOAs. As the related EP component, Nc, or the negative peak immediately following the click onset, was taken and the Nc recorded from Cz was analyzed. Although the larger Nc amplitudes occurred with shorter SRTs, no systematic changes in Nc amplitude were observed as a function of SOAs. Nc latencies, the variations of which were smaller for an intense click than for a faint one, were shorter for trials in whicli light preceded click (S0A<0) than for click-alone trials, in correlation with SRTs. This fact suggests that the light given prior to click increased the arousal level and/or the processing speed. Bimodal facilitating effect of the internal processing speed upon SRTs was obtained at 50ms of SOA.