Dipole analysis of ultralate (C-fibres) evoked potentials after laser stimulation of tiny cutaneous surface areas in humans

Ultralate (C-fibres) laser evoked potentials (LEP) can be obtained by stimu lation of a tiny skin surface area (0.23 mm(2)). Since their generators are unknown up to now, we performed brain source analyses of ultralate LEPs us ing high resolution electroencephalography (64 channels) and a realistic he ad model that was based on individual magnetic resonance images. Ultralate LEPs were characterized by a negative-positive complex with a large positiv e component maximal at the vertex. Source analysis revealed that ultralate LEPs could be explained by two dipole sources in the upper bank of the cont ralateral and ipsilateral Sylvian fissure (SII) and one dipole in the media n region corresponding to the anterior cingulate gyrus, (C) 2001 Elsevier S cience Ireland Ltd. All rights reserved.