Psychogalvanic response as a pain reaction component

¹ Laboratoire de Biophysique, Université de Louvain, Louvain, Belgium

Psychogalvanic responses (PGR) were measured in human subjects as response to cutaneous stimulation by thermal radiation. There were 37 subjects of both sexes, aged 18–40 years and there were 2054 presentations. An apparatus for recording PGR on an EEG tracing is described. Based on physical intensity of stimulus there is a complete overlap of pain-nonpain categories—from 35° to 55°C end temperature in irradiated skin. Plotting magnitude of PGR against physical intensity of stimulus for pain and nonpain categories reveals that intensity of reaction in pain is not determined by physical intensity of stimulus. When magnitude of reaction is compared as between pain and nonpain responses on the basis of the same stimulus intensities, it is found to be greater for pain to a highly significant extent; on the same basis, duration of response is longer for pain, but not at a high level of significance. The PGR is shown to be an accurate discriminator of the subjective pain sensation threshold. When electrocortical are compared to electrodermal reactions, both are found to be triggered in a consistent manner by the common stimulus, which consistency is reduced when the subject judges the stimulus painful. Effects of habituation are examined and shown not to be causal to results. Implications of the findings for the pain experience in the true life situation are discussed.