Disrutpted resting-state functional architecture of the brain after 45-day simulated microgravity

Abstract

Long-term spaceflight induces both physiological and psychological changes in astronauts. To understand the neural mechanisms underlying these physiological and psychological changes, it is critical to investigate the effects of microgravity on the functional architecture of the brain. In this study, we used resting-state functional MRI (rs-fMRI) to study whether the functional architecture of the brain is altered after 45 days of −6° head-down tilt (HDT) bed rest, which is a reliable model for the simulation of microgravity. Sixteen healthy male volunteers underwent rs-fMRI scans before and after 45 days of −6° HDT bed rest. Specifically, we used a commonly employed graph-based measure of network organization, i.e., degree centrality (DC), to perform a full-brain exploration of the regions that were influenced by simulated microgravity. We subsequently examined the functional connectivities of these regions using a seed-based resting-state functional connectivity (RSFC) analysis. We found decreased DC in two regions, the left anterior insula (aINS) and the anterior part of the middle cingulate cortex (MCC; also called the dorsal anterior cingulate cortex in many studies), in the male volunteers after 45 days of −6° HDT bed rest. Furthermore, seed-based RSFC analyses revealed that a functional network anchored in the aINS and MCC was particularly influenced by simulated microgravity. These results provide evidence that simulated microgravity alters the resting-state functional architecture of the brains of males and suggest that the processing of salience information, which is primarily subserved by the aINS–MCC functional network, is particularly influenced by spaceflight. The current findings provide a new perspective for understanding the relationships between microgravity, cognitive function, autonomic neural function, and central neural activity.

Default network connectivity decodes brain states with simulated microgravity

“…Liao et al (2013) tentatively used resting-state functional magnetic resonance imaging (fMRI) to investigate brain activity change after 3-day head down tilt (HDT) bed rest and observed decreased local activity in thalamus and declined regional homogeneity in left inferior parietal lobule which may attribute to reduced motor control abilities and declined abilities of mental transformation. Recently, Zhou et al (2014) carried out a groundbreaking research to discuss the effects of long-term microgravity on the functional architecture of the brain. In this 45-day HDT bed rest study, a functional network anchored in the anterior insula and middle cingulate cortex was found to be influenced by simulated microgravity.…”

“…In this 45-day HDT bed rest study, a functional network anchored in the anterior insula and middle cingulate cortex was found to be influenced by simulated microgravity. The authors suggested that these functional anomalies may reflect variation in cognitive function, autonomic neural function and central neural activity (Zhou et al 2014). In a recent study, Liao et al (2015) figured out the time trend of brain activity change in a 7-day HDT period.…”

Disrupted Resting-State Brain Functional Architecture in Amphetamine-Type Stimulant Abusers

“…A grey matter mask was used to exclude artifactual correlations from non-gray matter voxels as previously described [33,35].…”

“…Due to the inconsistent findings of previous rs-fMRI studies of ATSAs, this examination of voxel-wise DC allowed us to identify brain regions that might be influenced by amphetamine-type stimulants without requiring a priori selection of nodes or networks of interest. Next, seed-based RSFC analysis was used to further reveal the details of the functional networks that were associated with the identified regions [29,33].…”

“…We first used voxel-wise degree centrality (DC) analysis, a method that is widely used to detect changes in resting-state functional networks [29][30][31][32][33], to characterize the functional relationships of a given voxel (node) within the entire connectivity matrix of the brain [29,34,35]. Due to the inconsistent findings of previous rs-fMRI studies of ATSAs, this examination of voxel-wise DC allowed us to identify brain regions that might be influenced by amphetamine-type stimulants without requiring a priori selection of nodes or networks of interest.…”