High Gamma Activity in Response to Deviant Auditory Stimuli Recorded Directly From Human Cortex

TLDR

Electrophysiological responses were recorded from the left frontal and temporal cortex of awake neurosurgical patients to repetitive background and rare deviant auditory stimuli. Prominent ERPs were recorded from auditory association cortex and adjacent temporal regions, with deviant stimuli eliciting a longer‑latency mismatch response maximal anteriorly; low‑gamma (30–60 Hz) and high‑gamma (60–250 Hz) oscillations were observed, while frontal sites showed no reliable sensory or mismatch potentials, suggesting high‑gamma activity represents sensory‑induced neocortical ripples akin to hippocampal ripples.

Abstract

We recorded electrophysiological responses from the left frontal and temporal cortex of awake neurosurgical patients to both repetitive background and rare deviant auditory stimuli. Prominent sensory event-related potentials (ERPs) were recorded from auditory association cortex of the temporal lobe and adjacent regions surrounding the posterior Sylvian fissure. Deviant stimuli generated an additional longer latency mismatch response, maximal at more anterior temporal lobe sites. We found low gamma (30-60 Hz) in auditory association cortex, and we also show the existence of high-frequency oscillations above the traditional gamma range (high gamma, 60-250 Hz). Sensory and mismatch potentials were not reliably observed at frontal recording sites. We suggest that the high gamma oscillations are sensory-induced neocortical ripples, similar in physiological origin to the well-studied ripples of the hippocampus.