Comparative source localization of electrically and pressure-stimulated multichannel somatosensory evoked potentials.

The purpose of the study was to determine if there is a difference in the determination of the cortical hand area by dipole source estimation after artificial and natural stimuli. In principle, there are advantages of both methods: pressure stimulation is less invasive and compatible to fMRI, whereas electrical stimulation can be applied with higher stimulus rates and elicits sharper waveforms. Electrical and pressure stimulation was performed simultaneously on the thumb and fifth finger on eight healthy volunteers. The somatosensory evoked potentials after electrical stimulation showed sharper peaks and higher amplitudes than the pressure stimulated potentials. For the two stimulus qualities, cortical source positions of thumb and fifth finger separated significantly in the vertical z-axis. Both methods deliver reliable stimulation and therefore allow separate source localization of thumb and fifth finger. For cortical plasticity studies, peripheral somatosensory stimulation is of great importance. According to these findings, the choice of method, electrical or mechanical stimulation, may depend on practical criteria.