Augmenting-reducing of the visual evoked potential as a function of changes in skin conductance level.

Abstract

ABSTRACTIn the first of two experiments four visual evoked potential (VEP) measures of augmenting‐reducing were made consecutively within a single test session on each of 10 student volunteers, on whom palmar skin conductance, taken as an index of arousal, was also monitored continuously. Regression slopes relating VEP amplitude to stimulus intensity for any given individual were found to vary considerably over the session, some subjects changing from augmenting to reducing (or vice versa) during testing. Further analysis of the within‐subject data indicated that shifts in augmenting‐reducing were related to changes in skin conductance level (SCL) and to the range of SCL over which individuals were operating in relation to the group. Thus, subjects in the high SCL range shifted toward relative reducing as their conductance level increased and those in the low SCL range toward relative augmenting. These effects were exactly replicated in a second experiment using a further 10 subjects and a virtually identical procedure. It was concluded that augmenting‐reducing is partly state‐dependent, though in a manner which is systematic enough to warrant its further investigation in studies focusing on the dynamic aspects of stimulus modulation.