Whole head mapping of magnetic fields following painful electric finger shock.

Painful intracutaneous electric finger shock was delivered to the fifth digit of the non-dominant hand of five healthy volunteers. Whole head evoked magnetic field maps were collected and cortical localizations were calculated using local sphere equivalent current dipole fits. MRI scans were used to identify the anatomical structures where magnetic field sources were located. Anatomically, sources were identified bilaterally in the primary somatosensory region and SII-Insula regions. Additionally, frontal operculum sources were observed contralaterally in two subjects. Temporally, an initial contralateral SI activation at 40-60 ms was followed by several SII-Insula responses over the next several hundred milliseconds (ms). These SII-Insula responses were often interspersed with additional activations of the SI region. These later responses were observed in both hemispheres.