[Estimation of neural generators of cognitive potential P300 by dipole tracing method]

A computer-aided method dipole tracing system, allows to estimate the location of the generator of brain potentials and has the advantage of non-invasive recording in physiological state. In this experiment, a two-dipole model and a four-dipole model of the active electrical sources of the cognitive component P300 of event related potentials have been examined by using dipole tracing method in normal human subjects. We have recorded P300 in a group of 3 healthy females aged 19-24 years, using somatosensory stimuli requiring a button-press response. The brain potentials were recorded with 21 surface electrodes placed over the scalp. Three-dimensional coordinates of surface electrodes and scalp, skull and brain (SSB) geometry of the subjects were measured by special device and three-dimensional MRI images, respectively. In order to estimate the localization of active dipoles, the conductivities of the scalp, the skull and the brain were approximated to be 1: 1/80: 1. In the present study, with data derived from all 21 channels, the sources of individual P300 components were analyzed during 10-30 msec at every 1 msec intervals. As a result, the dipole locations for each subjects were similar both in the two dipole model and in the four dipole model. The calculation on two dipole model showed the generators of P300 situated symmetrically in the frontal lobe. Whereas, the calculation on four dipole model showed them situated symmetrically near the hippocampus and in the parietal cortex which were close to the neural generators of P300 reported by other authors.(ABSTRACT TRUNCATED AT 250 WORDS)