The origin of pattern reversal short latency visual evoked potential as determined by dynamic topography and the dipole tracing method.

The generator sites of the parietal P59 and occipital N26 components elicited by hemi-field pattern reversal stimuli were investigated. The topographic distribution of the occipital N26 component showed a paradoxical lateralization, whereas that of the parietal P59 component exhibited an anatomical lateralization. The equivalent dipoles of both occipital N26 and parietal P59 components were situated on the deep mesial surface of the functioning occipital lobe. The differences in these locations were not statistically significant, but the vector moment of the parietal P59 component projected toward the functioning parieto-occipital region and one of the occipital N26 components projected away from the functioning occipital region. The generator sites of the short latency component were considered to differ from those of the middle latency visual evoked potential. Therefore both the occipital pole and the deep cerebral structure, i.e., the lateral geniculate nucleus, may play a role in the generation of equivalent dipoles.