AUGMENTING AND REDUCING IN AVERAGED VISUAL EVOKED RESPONSES TO SINE WAVE LIGHT

It has been reported that the change in averaged visual evoked response (VER) amplitude with change in light flash intensity is related to a measure of kinesthetic figural after effects. It has also been reported that in some subjects, the amplitude of VER to sine wave light may decrease as depth of modulation approaches 100%. This study attempted to examine the change in VER amplitude resulting from change in depth of sine wave modulation on the one hand, and a measure of kinesthetic figural after effects (referred to as the bar test) on the other. The VER amplitudes to the six depths of modulation were plotted as a ftmction of depth of modulation, and the slope of that function served as an index of VER “augmentation” and “reduction.” The bar test was also scored to yield an index of kinesthetic “augmentation” and “reduction.” There was a rank correlation of .66 (p < .01 for N = 30) between VER slopes and bar test scores. Test‐retest values for eleven subjects show that VER slopes and bar scores changed together and that order of test day apparently had no regular effect. The administration of phenylephrine to dilate pupils produced a steeper VER slope, that is, a greater “augmentation,” in all six subjects tested. These results are discussed in terms of a general stimulus intensity control mechanism which influences sensory responsivity across modalities. Copyright © 1969, Wiley Blackwell. All rights reserved