EEG Functional Connectivity is a Weak Predictor of Causal Brain Interactions.

Area of Science:

• Neuroscience
• Brain Imaging
• Computational Neuroscience

Background:

• Resting-state functional connectivity (FC) research using various modalities has rapidly expanded.
• The relationship between measured FC and underlying causal brain interactions remains poorly understood.

Purpose of the Study:

• To investigate the link between electroencephalography (EEG) resting-state FC and the propagation of transcranial magnetic stimulation (TMS) evoked potentials (TEPs).
• To assess this relationship at both sensor and source levels in healthy participants.

Main Methods:

• Simultaneous EEG and TMS were used in ten healthy individuals, with TMS applied to six cortical regions.
• Pre-stimulus FC was calculated using five different metrics (Pearson's correlation, mutual information, weighted phase lag index, coherence, phase locking value).
• TEP propagation was quantified using root mean square (RMS) of voltage and current source density (CSD), analyzed with generalized linear models (GLM).

Main Results:

• All tested FC measures significantly correlated with TEP activity at both sensor and source levels across early (15-75 ms) and full (15-400 ms) time ranges.
• However, FC measures explained less than 10% of the variance in TEP activity.
• The predictive power of FC measures varied considerably between participants and stimulation sites.

Conclusions:

• While EEG-based resting-state FC correlates with TMS-evoked brain activity, its predictive capacity is limited.
• These findings highlight the need for cautious interpretation of EEG FC in both sensor and source space analyses.
• Further research is needed to fully elucidate the relationship between functional connectivity and causal brain interactions.