Objective: The second exteroceptive suppression (ES2) is assumed to be an indicator of central antinociceptive processing, although some conflicting data have been produced. We examined the impact of experimentally induced psychophysiological conditions on the latency and duration of the ES2. Also, the association to the subjective evaluation of the painful electrical stimulation by which the ES2 is elicited was studied.
Methods: ES2 was assessed in 46 healthy volunteers running through four experimentally induced psychophysiological conditions: stress, relaxation, depressed mood, and heterotopic pressure pain. Conditions were presented in a repeated measure design in permuted sequences. Ten stimulation-recording sequences per condition were averaged. ES2 parameters were compared to a baseline condition and correlated to subjective pain perception.
Results: ES2 duration was found to be prolonged and ES2 latency to be shortened under the impact of relaxation and depressed mood. The subjective perception of the painful electrical stimulation was affected by the experimental conditions.
Conclusion: Data lend support to the hypothesis that the repeatedly observed limited stability of ES2 parameters might be caused by the variability of individual psychophysiological states. Against expectation, subjective pain perception is not systematically correlated with ES2 parameters. Thus it can be questioned whether the ES2 is directly associated with pain processing at all.