Reduced frontal theta oscillations indicate altered crossmodal prediction error processing in schizophrenia

Area of Science:

• Neuroscience
• Psychiatry
• Cognitive Science

Background:

• The brain predicts incoming stimuli, and prediction errors (PE) are crucial for learning.
• Deficits in PE processing may underlie hallucinations and delusions in schizophrenia (SZ).
• Previous research focused on unisensory PE processing, leaving crossmodal PE in SZ largely unexplored.

Purpose of the Study:

• To investigate crossmodal prediction error processing in individuals with schizophrenia (SZP) compared to healthy controls (HC).
• To examine neural activity during audiovisual speech perception using high-density electroencephalography (EEG).
• To identify potential neural correlates of multisensory processing deficits in SZ.

Main Methods:

• Utilized a paradigm pairing visual syllables with congruent or incongruent auditory syllables, varying visual predictability.
• Measured high-density EEG and applied source estimation to analyze event-related potentials (ERPs) and neural oscillations.
• Compared ERPs and theta-band (4-7 Hz) oscillations between incongruent and congruent stimuli across predictive levels in SZP and HC.

Main Results:

• Both SZP and HC exhibited larger ERPs for high-predictive compared to low-predictive syllables, indicating intact audiovisual incongruence detection in the auditory cortex.
• Healthy controls showed enhanced frontal theta-band oscillations for high-predictive stimuli, reflecting successful crossmodal PE processing.
• This frontal theta-band enhancement was absent in SZP, suggesting a deficit in crossmodal PE processing.

Conclusions:

• SZP demonstrate intact early audiovisual incongruence detection but impaired crossmodal prediction error processing.
• Aberrant frontal theta-band oscillations in SZP are linked to crossmodal PE processing deficits.
• The findings suggest a top-down multisensory processing deficit and highlight the role of dysfunctional frontal oscillations in schizophrenia psychopathology.