DIFFERENTIAL-EFFECTS OF DISTINCT BRAIN-LE SIONS ON EVENT-RELATED POTENTIALS - A P300 STUDY

In order to identify the neural structures which may be involved in th e generation of the P300, 73 patients with focal brain damage were tes ted using an auditory ''oddball''-paradigm. Included were fourteen pat ients with frontal, ten with parietal and sixteen with subcortical les ion sites. The latency of the P3b in the grand averages was delayed by approximately 20 ms in all patient groups compared to the control gro up (n = 12) a nd the amplitude of the P3b was significantly reduced. I n addition we found differential effects according to lesion sites. Fr ontal damage resulted in a prolonged latency and reduced amplitude of the NZ in frontal areas, whereas the P3b was quite normal in the parie tal region. The opposite was found for patients with parietal lesions: a frontal increased amplitude of the NZ was combined with a decreased parietal P3b amplitude. Subcortical lesions exhibited an irradiation of the N2 with increased amplitude from the frontal to the parietal ar eas. Our results indicate that subcortical structures play a central r ole in the generation or modulation of the P3-complex.