Electroacupuncture modulates cortical activities evoked by noxious somatosensory stimulations in human

A noninvasive high-resolution imaging technique of cerebral electric activities has been developed to directly link scalp potential measurement with the magnetic resonance images of the subjects, which is very helpful for the elucidation of the cortical processing following various stimulations. Here, we used a 64-channel Neuroscan ESI-128 system to explore the specific cortical activities elicited by electroacupuncture (EA) acupoint in normal volunteers and the modulatory effect of EA on cortical activities evoked by noxious somatosensory stimulation. A specific later-latency somatosensory-evoked potential (SEP, P150) located in bilateral anterior cingulated cortex was observed after EA acupoint but not non-acupoint. Two pain-specific SEP components (P170 and N280), located in bilateral suprasylvian operculum and anterior cingulated cortex respectively were observed following painful median nerve stimulation. Binding EA acupoint with painful median nerve stimulation, the amplitudes of P170 and N280 appeared to be attenuated significantly, 2D topography exhibited tremendous decrease of cortical activation between 120 ms and 296 ms in latency, and visual analogue scale (VAS) changes also showed a similar pattern to the change of amplitude. The bilateral anterior cingulated cortex recruited following acupoint stimuli might, to some extent, suggest that EA has the specific physiological effects. Decrease of pain-induced cortical activation by EA acupoint was considered to be mainly due to an interaction of the signals in anterior cingulated cortex ascending from the pain stimulation and EA.