Habituation of the orienting response as reflected by the skin conductance response and by endogenous event-related brain potentials.

The paper is concerned with the question of whether endogenous components of the auditory event-related brain potential (ERP) qualify for showing habituation of the orienting response (OR). Although response decrements have been found in nearly every ERP component, this question is still of current concern because a true selective response inhibition proving habituation of the OR is still lacking. The question has been tackled using single-trial ERP measurements in classical variants of the repetition/change paradigm commonly used in the traditional OR research on autonomous responses such as the skin conductance response (SCR). Results on 120 adults indicate that at least two endogenous components of the ERP, an anterior slow negative wave and a posterior slow positive wave, meet essential requirements of habituation: like the exemplary OR component, the SCR, both slow waves declined systematically with repeated stimulations and, more than that, recovered in response to fundamental changes. In the same way, an anterior positivity resembling the novelty P3 levelled off systematically with the stimulations, but without showing recovery. Thus, in so far as habituation of the OR is conceptualised as a selective inhibitory central nervous system process which can be assumed to have taken place only if a systematic (usually exponential) response decrement is followed by a recovery, the generalised decrement of the P3 cannot be equated with habituation, whereas the selective response diminution of both slow waves would have to be regarded as typical of habituation.