Mapping of early and late human somatosensory evoked brain potentials to phasic galvanic painful stimulation

In the present study, we modeled the spatiotemporal evolution of human soma tosensory evoked cortical potentials (SEPs) to brief median-nerve galvanic painful stimulation. SEPs were recorded (-50 to +250 ms) from 12 healthy su bjects following nonpainful (reference), slight painful, and moderate painf ul stimulations (subjective scale). Laplacian transformation of scalp SEPs reduced head volume conduction effects and annulled electric reference infl uence. Typical SEP components to the galvanic nonpainful stimulation were c ontralateral frontal P20-N30-N60-N120-P170, central P22-P40, and parietal N 20-P30-P60-P120 (N = negativity P = positivity number = latency in ms). The se components were observed also with the painful stimulations, the N60, N1 20, P170 having a longer latency with the painful than nonpainful stimulati ons. Additional SEP components elicited by the painful stimulations were pa rietomedian P80 as well as central N125, P170 (cP170), and P200. These addi tional SEP components included the typical vertex negative-positive complex following transient painful stimulations. Latency of the SEP components ex clusively elicited by painful stimulation is highly compatible with the inv olvement of A delta myelinated fibers/spinothalamic pathway. The topography of these components is in line with the response of both nociceptive media l and lateral systems including bilateral primary sensorimotor and anterior cingulate cortical areas. The role of attentive, affective, and motor aspe cts in the modulation of the reported SEP components merits investigation i n future experiments. Hum. Brain Mapping 12:168-179, 2001. (C) 2001 Wiley-L iss, Inc.