Fig. (4) P1 and N2 amplitudes plotted as a function of electrode location for luminance, L-M and S/(L+M) stimuli of varying contrast. The contrast values for the luminance stimuli are in terms of Michelson contrast, those for the L-M and S-(L+M) chromatic stimuli are given in terms of a computed cone contrast value (see text for details). Data are shown for moving stimuli of relatively high (10 deg/sec), medium (5 deg/sec) and low (2 deg/sec) speed.