Spontaneous eye movements during eyes-open rest reduce resting-state-network modularity by increasing...

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Functional Neuroimaging

Background:

• During wakeful rest, individuals exhibit small, endogenously driven eye movements.
• These oculomotor patterns have been largely overlooked in resting-state functional magnetic resonance imaging (fMRI) studies.
• Previous research utilized eye-orbit echo-planar imaging (EO-EPI) signals to detect exogenous eye movements.

Purpose of the Study:

• To investigate the impact of endogenous eye movements on the topography and topology of functional brain networks during wakeful rest.
• To determine if EO-EPI signals, indicative of eye movements, correlate with resting-state (RS) fMRI data.
• To assess how accounting for oculomotor-related variance affects the interpretation of RS network structure.

Main Methods:

• Analysis of eyes-open resting-state fMRI data simultaneously acquired with eye-tracking.
• Correlation analysis between eye-tracking data, RS BOLD signals, and EO-EPI time series.
• Partialling out EO-EPI variance from RS data to examine changes in functional connectivity and network metrics (modularity, connectivity strength, clustering coefficient).

Main Results:

• Eye-tracking data showed modest correlation with RS BOLD but strong correlation with EO-EPI signals.
• EO-EPI data correlated with activity in sensorimotor and attention networks, including frontal eye fields.
• Removing EO-EPI variance reduced sensorimotor-visual connectivity and increased network modularity, while decreasing mean connectivity strength and clustering coefficients.

Conclusions:

• Endogenous eye movements during wakeful rest are a significant contributor to functional brain network topology.
• Oculomotor-related signals, captured by EO-EPI, are an important component of resting-state networks.
• These findings necessitate consideration of eye movement contributions when interpreting RS network differences across conditions or populations.