The Scanner as the Stimulus: Deficient Gamma-BOLD Coupling in Schizophrenia at Rest.

Area of Science:

• Neuroscience
• Psychiatry
• Medical Imaging

Background:

• Functional magnetic resonance imaging (fMRI) is crucial for schizophrenia (SZ) research but its loud scanner environment may affect results.
• Sensory processing abnormalities in SZ could interact with scanner noise, potentially confounding fMRI findings.
• Resting-state fMRI (rs-fMRI) is widely used in SZ research, necessitating an understanding of scanner noise effects.

Purpose of the Study:

• To investigate the impact of scanner background sound on neural and hemodynamic activity in individuals with SZ.
• To determine if sensory processing deficits in SZ are exacerbated by the fMRI environment.
• To refine the construct validity of the MR neuroimaging environment for SZ research.

Main Methods:

• Simultaneous electroencephalography (EEG)-fMRI was recorded during resting-state scans in individuals with SZ (n=57) and healthy controls (n=46).
• Gamma EEG activity was analyzed in relation to scanner noise frequencies.
• Gamma-hemodynamic coupling was assessed in auditory regions, specifically the superior temporal gyri.

Main Results:

• Reduced gamma-hemodynamic coupling was observed in the bilateral auditory superior temporal gyri of participants with SZ compared to controls.
• This impaired coupling occurred in the frequency range of the scanner's background sound.
• Reduced gamma-hemodynamic coupling correlated with sensory gating deficits and greater symptom severity in SZ.

Conclusions:

• Fundamental sensory-neural processing deficits in SZ are evident even at rest when scanner noise is considered a stimulus.
• The findings suggest that scanner background sound can be a confounding variable in rs-fMRI studies of SZ.
• Future SZ neuroimaging research should account for scanner noise's potential influence on neural excitability and arousal.