Spurious correlations in simultaneous EEG-fMRI driven by in-scanner movement.

Area of Science:

• Neuroscience
• Cognitive Science
• Biomedical Engineering

Background:

• Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) offer high temporal and spatial resolution for studying cognitive processes.
• MR scanner-induced artifacts in EEG data remain a significant challenge for accurate interpretation.

Purpose of the Study:

• To investigate the impact of head motion, a commonly overlooked artifact source, on EEG data and EEG-BOLD correlations in simultaneous EEG-fMRI.
• To demonstrate how minor head movements can introduce spurious findings in cognitive neuroscience research.

Main Methods:

• Applied standard artifact correction techniques to simultaneous EEG-fMRI data.
• Analyzed the correlation between low-frequency EEG (<20Hz) and in-scanner head motion.
• Examined EEG-BOLD correlations in relation to motion-fMRI correlations.
• Utilized a memory encoding experiment to illustrate the findings.

Main Results:

• Low-frequency EEG signals (<20Hz) showed a strong correlation with in-scanner movement.
• Minor head motion (<0.2mm) generated spurious low-frequency EEG effects and influenced EEG-BOLD correlations.
• Observed that EEG-BOLD correlations closely mirrored motion-fMRI correlations.
• Demonstrated that theta power effects and theta-BOLD correlations in a memory task reflected scanner motion.

Conclusions:

• Head motion is a critical, often underestimated, source of artifacts in simultaneous EEG-fMRI studies.
• Spurious EEG effects and correlations can arise from even subtle head movements, potentially misrepresenting cognitive processes.
• Future EEG-fMRI research must rigorously address and account for head motion to ensure data validity.