Abstract
[Diminution of Electrodermal Responses to Painful Stimuli During Pavlovian Conditioning]
UCR-diminution refers to a decline in responding to UCSs during Pavlovian conditioning. As regards psychophysiological indices (e.g., skin conductance response; SCR), UCR-diminution has been regularly documented in human studies. It is, however, unclear whether or not UCR-diminution is also manifest in subjective evaluations of UCSs (e.g., aversiveness, painfulness etc.). A considerable number of studies failed to document such a subjective component of UCR-diminution. However, several of these studies deviated from the traditional Pavlovian conditioning set-up. The present study (N = 20) sought to answer the question whether UCR-diminution can be found in subjective pain ratings. One group of normal subjects (conditioning group) received paired CS (triangle)-UCS (electric shock) trials. Interstimulus intervals were 4 sec. The other group (habituation group) received explicitly unpaired CS and UCS presentations. SCRs were measured throughout the experiment. Subjects were also asked to rate the painfulness of each UCS (shock) that occurred. The results showed that in the conditioning group, a conditioned SCR to the CS was accompanied by a significant reduction of the SCR to the UCS. These effects did not occur in the habituation group. Most importantly, in the conditioning group the subjective evaluations of the UCSs did not parallel the physiological (SCR) UCR-diminution. Thus, no evidence was found for a subjective component in UCR-diminution. The relevance of these findings for a classical learning interpretation of chronic pain is discussed.