High gamma activity in response to deviant auditory stimuli recorded directly from human cortex

Area of Science:

• Neuroscience
• Electrophysiology
• Auditory Neuroscience

Background:

• Understanding human auditory processing is crucial for diagnosing and treating neurological disorders.
• Electrophysiological responses, such as event-related potentials (ERPs), provide insights into neural activity.
• The role of high-frequency oscillations in auditory perception remains an active area of research.

Purpose of the Study:

• To record and analyze electrophysiological responses to auditory stimuli in awake neurosurgical patients.
• To investigate the presence and characteristics of both low and high-frequency oscillations in the auditory cortex.
• To explore the neural basis of sensory processing and mismatch responses in the human brain.

Main Methods:

• Electrophysiological recordings from the left frontal and temporal cortex of awake neurosurgical patients.
• Presentation of repetitive background and rare deviant auditory stimuli.
• Analysis of sensory event-related potentials (ERPs) and high-frequency oscillations (gamma and high gamma bands).

Main Results:

• Prominent sensory ERPs and low gamma oscillations (30-60 Hz) were recorded in the auditory association cortex.
• A longer latency mismatch response was observed for deviant stimuli, maximal at anterior temporal lobe sites.
• High-frequency oscillations (high gamma, 60-250 Hz) were detected, potentially representing neocortical ripples.

Conclusions:

• The temporal cortex exhibits distinct electrophysiological responses to auditory stimuli, including sensory potentials and mismatch responses.
• High-frequency oscillations above the traditional gamma range were identified in the auditory association cortex.
• These high gamma oscillations may be sensory-induced neocortical ripples, analogous to hippocampal ripples.