Infarction of the superior temporal gyrus: a description of auditory evoked potential latency and amplitude topology.

P1 and N1 of the cortical auditory evoked potential (AEP) were studied with multiple electrodes in 10 normal subjects and 6 patients with left middle cerebral artery infarction. Patients were selected based on neurological examination and on CT scans showing both (1) infarction limited to the vascular territory and (2) involvement of posterior portion of superior temporal gyrus. Waveforms recorded from C3, Cz, and C4 were examined for peak latency and amplitude of P1 and N1 on all subjects. Topographic displays of amplitude over P1 and N1 latency ranges were also examined. In normals, P1 was identified in 9 of the 10 subjects at all three electrode sites. In patients, P1 was identified at C3 in only 1 of the 6. N1 was present at all three electrodes in the 10 normal subjects and in 5 of the 6 patients. The remaining patient had N1 at C4 and Cz only. Examination of amplitude topology showed as asymmetric evolution of P1 and N1 in the patients. This asymmetry was not present in normals. The results of this study are consistent with theory that P1 arises from primary auditory cortex. Results further suggest multiple generators for N1. Additional study correlating topographic display from multichannel recordings with CT or MRI in brain-injured patients may bring more insight into N1 generators.