Correlation of subjective pain experience with cerebral evoked responses to noxious thermal stimulations.

The relationships between different parameters of the evoked cerebral response to noxious thermal stimulation, stimulus intensity, and subjective pain were investigated in seven normal human volunteers. The evoked response was characterized by late events: a small negative peak at 164--180 ms, followed by a high amplitude positive peak at 372--391 ms. The only correlation found in this study was between the amplitude of the positive component and the qualitative and quantitative aspects of the verbal report of pain. This was manifested by a linear trend of association: an increase in the evoked response amplitude was accompanied by an increase in the magnitude of the subjective sensation. The findings suggest that the evoked response to noxious heat reflects not a mere transduction of the physical parameters of the stimulus, but rather a complex interpretative action at the cerebral level.