EEG coherence measures during auditory hallucinations in schizophrenia

Area of Science:

• Neuroscience
• Psychiatry
• Cognitive Science

Background:

• Auditory hallucinations (AHs) are a core symptom of schizophrenia.
• Dominant models for AHs include the inner speech and central auditory processing deficit (CAPD) models.
• Understanding the neural underpinnings of AHs is crucial for developing targeted treatments.

Purpose of the Study:

• To investigate changes in EEG alpha-band coherence during auditory hallucination (AH) and non-auditory hallucination (non-AH) states in schizophrenia patients.
• To examine functional connectivity between key cortical regions implicated in auditory processing and speech production.
• To evaluate the findings in relation to the inner speech and CAPD models of auditory hallucinations.

Main Methods:

• Electroencephalography (EEG) alpha-band average coherence was measured in seven schizophrenia patients experiencing auditory hallucinations.
• Coherence was analyzed between Broca's area (BA 44/45) and Wernicke's area (BA 22/42), and between left and right superior temporal cortices.
• Relative power in auditory cortical regions was also assessed during AH and non-AH states.

Main Results:

• No significant change in coherence was found between Broca's and Wernicke's areas.
• A significant increase in coherence was observed between the left and right superior temporal cortices during AHs compared to non-AHs.
• Increased relative power was noted in the left auditory cortex during AHs, but not the right.

Conclusions:

• Findings suggest abnormally increased synchrony between the left and right auditory cortices during auditory hallucinations in schizophrenia.
• The results support the central auditory processing deficit (CAPD) model.
• The observed patterns are consistent with theories postulating reduced prosodic processing during auditory hallucinations.