High resolution recording of late cortical surface potentials N1 and gamma band response (GBR)

The present investigation was conducted to help determine whether source activity of the direct recorded N1 response differed from that of the gamma band response (GBR). Auditory evoked cortical potential data from two patients with intractable epilepsy undergoing prolonged video EEG monitoring after implantation of subdural electrodes is reported in this investigation. Evoked responses were recorded to 1000-Hz tone bursts. The data were then filtered digitally to resolve the GBR. The voltage fields were subsequently viewed topographically. Although both responses originated in the supratemporal cortex, the N1 and GBR voltage field patterns differed. These results are consistent with the view that the sources of N1 and the GBR are different, suggesting that these components emanate from functionally distinct neuronal pools.