True associations between resting fMRI time series based on innovations

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Brain Imaging

Background:

• Resting-state functional magnetic resonance imaging (fMRI) measures spontaneous brain activity.
• Understanding functional connectivity requires analyzing complex relationships between brain regions.
• Anatomical connectivity provides a structural basis for functional interactions.

Purpose of the Study:

• To investigate voxel-by-voxel cross-correlations in resting-state fMRI data.
• To examine how functional interactions relate to anatomical connectivity.
• To identify systematic patterns in functional connectivity across different brain regions.

Main Methods:

• Calculated pairwise cross-correlations between prewhitened BOLD fMRI time series from 60 cortical areas in 18 subjects.
• Computed cross-correlatgrams for each pair, analyzing peak values, lags, and signs.
• Grouped voxel pairs based on anatomical connectivity: within-area, homotopic, ipsilateral, and contralateral.

Main Results:

• Most cross-correlation peaks occurred at zero or ±1 lag.
• Positive cross-correlations were more frequent than negative ones across all groups.
• Average cross-correlation strength and the ratio of positive to negative correlations decreased progressively from within-area to contralateral connections.
• Functional connectivity patterns systematically varied with brain group and lag, correlating with anatomical connectivity density.

Conclusions:

• Functional interactions between brain voxels exhibit systematic patterns related to their location and lag.
• The density of anatomical connectivity appears to be a significant determinant of functional interactions between brain areas.
• These findings highlight the structural underpinnings of large-scale brain functional organization.