Dipolar source modeling of the P300 event-related potential after somatosensory stimulation

The cerebral generators of the P300 potential evoked by somatosensory stimuli were investigated. Event-related potentials elicited by an oddball paradigm were recorded in 15 healthy subjects by 19 scalp electrodes. Nontarget and target electric stimuli were delivered on the anterior surface of the left elbow and of the wrist, respectively. Target traces showed an N140 potential followed by a widely distributed P300 response. Dipolar source modeling of target traces resulted in a six-dipole model. In the earlier latency range (up to 200 ms), one dipole in the contralateral perirolandic region and two dipoles in the parasylvian cortex of both hemispheres were activated. Two dipolar sources located bilaterally in the medial temporal region (MTR) showed their maximal activity at the P300 latency. Finally, a dipole in the contralateral frontal lobe was activated both at the latency of the N140 response and after 200 ms. It was found that two symmetrical MTR sources and a frontal dipole contributed to P300 generation.