Left auditory cortex gamma synchronization and auditory hallucination symptoms in schizophrenia

Area of Science:

• Neuroscience
• Psychiatry
• Biomedical Engineering

Background:

• Oscillatory electroencephalogram (EEG) abnormalities indicate neural circuit dysfunction in neuropsychiatric disorders.
• Previous research linked beta and gamma oscillation synchrony to hallucinations in schizophrenia.
• This study investigates the link between the 40 Hz auditory steady-state response (ASSR) and auditory hallucinations.

Purpose of the Study:

• To test if the 40 Hz ASSR in the left auditory cortex correlates with auditory hallucination severity in schizophrenia.
• To explore if the 40 Hz ASSR deficit in schizophrenia involves cross-frequency interactions.

Main Methods:

• Recorded EEG from 16 healthy controls (HC) and 18 schizophrenia patients (SZ) exposed to 40 Hz binaural click trains.
• Applied a 5-dipole model to auditory steady-state response (ASSR) data and performed time-frequency decomposition.
• Analyzed phase locking factor (PLF) and evoked power in both scalp and source EEG data.

Main Results:

• Reduced phase locking factor (PLF) and evoked power were observed in schizophrenia patients (SZ) at fronto-central electrodes.
• SZ showed reduced PLF in non-homologous left and right hemisphere sources.
• Left hemisphere source PLF in SZ positively correlated with auditory hallucination severity and was modulated by delta phase.

Conclusions:

• Schizophrenia exhibits differential neural circuit abnormalities in the left and right auditory cortices.
• Findings support the hypothesis that hallucinations are linked to cortical hyperexcitability and increased high-frequency synchronization in sensory areas.