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

Yuan Zhou,Yan-Qiang Bai,Shu Li,Yun Wang,Zhi-Qiang Tian,Zhu-Yuan Liang,Chun-Hui Wang,Xiao-Ping Chen,Dang Zheng,Cheng Tan,Li-Lin Rao,Shan-Guang Chen

doi:10.3389/fnbeh.2014.00200

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.

Highlights

With the launch of the first manned spaceflight by the Soviet Union on the 12th of April 1961 with cosmonaut Yuri Gagarin aboard, it became possible to travel beyond Earth’s gravity
To understand the neural mechanisms underlying these physiological and psychological changes, it is critical to investigate the effects of microgravity on brain activity from the brain network perspective because our understanding of the functioning of the human brain depends upon our knowledge of large-scale brain organization (Bressler and Menon, 2010)
Paired sample T-test showed that there were no significant differences for both the positive affect (t = −1.098, p = 0.289) and negative affect (t = 1.731, p = 0.104), which indicates that the participants did not have significant emotional changes after the head-down tilt (HDT) bed rest

Summary

Introduction

With the launch of the first manned spaceflight by the Soviet Union on the 12th of April 1961 with cosmonaut Yuri Gagarin aboard, it became possible to travel beyond Earth’s gravity. The success of interplanetary spaceflight will depend upon whether humans can function normally within an environment of microgravity and confinement (Basner et al, 2013). To understand the neural mechanisms underlying these physiological and psychological changes, it is critical to investigate the effects of microgravity on brain activity from the brain network perspective because our understanding of the functioning of the human brain depends upon our knowledge of large-scale brain organization (Bressler and Menon, 2010). We hypothesize that studies of the effects of microgravity on the intrinsic functional architecture of the brain may provide valuable insight into the neural mechanisms underlying the physiological and psychological changes that occur in microgravity

Methods

Results

Conclusion