Propagating patterns of intrinsic activity along macroscale gradients coordinate functional connections across the whole brain

• Type of Material: Article
• Authors: Behnaz Yousefi, Emory University; Shella Keilholz, Emory University
• Language: English
• Date: 2021-02-23
• Publisher: ACADEMIC PRESS INC ELSEVIER SCIENCE
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2021 Published by Elsevier Inc.
• License: Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1016/j.neuroimage.2021.117827
• Title of Journal or Parent Work: NEUROIMAGE
• Volume: 231
• Start Page: 117827
• End Page: 117827
• Grant/Funding Information: NIH R01MH111416 and R01NS078095.
• Keywords: Neurosciences; Life Sciences & Biomedicine; MODE; CORTEX; QUASI-PERIODIC PATTERNS; Neuroimaging; Science & Technology; NETWORK; RATS; SPATIOTEMPORAL DYNAMICS; Neurosciences & Neurology; RESTING-STATE FMRI; Radiology, Nuclear Medicine & Medical Imaging; ORGANIZATION; FLUCTUATIONS

Abstract

The intrinsic activity of the human brain, observed with resting-state fMRI (rsfMRI) and functional connectivity, exhibits macroscale spatial organization such as functional networks and gradients. Dynamic analysis techniques have shown that functional connectivity is a mere summary of time-varying patterns with distinct spatial and temporal characteristics. A better understanding of these patterns might provide insight into aspects of the brain's intrinsic activity that cannot be inferred by functional connectivity or the spatial maps derived from it, such as functional networks and gradients. Here, we describe three spatiotemporal patterns of coordinated activity across the whole brain obtained by averaging similar ~20-second-long segments of rsfMRI timeseries. In each of these patterns, activity propagates along a particular macroscale functional gradient, simultaneously across the cerebral cortex and in most other brain regions. In some regions, like the thalamus, the propagation suggests previously-undescribed gradients. The coordinated activity across areas is consistent with known tract-based connections, and nuanced differences in the timing of peak activity between regions point to plausible driving mechanisms. The magnitude of correlation within and particularly between functional networks is remarkably diminished when these patterns are regressed from the rsfMRI timeseries, a quantitative demonstration of their significant role in functional connectivity. Taken together, our results suggest that a few recurring patterns of propagating intrinsic activity along macroscale gradients give rise to and coordinate functional connections across the whole brain.