Changes of EEG beta band power and functional connectivity during spaceflight: a retrospective study

Abstract

Spaceflight exposes astronauts to unique conditions like microgravity, which may affect brain function, though it remains underexplored compared to other physiological systems. Astronauts often report temporary neurological symptoms, such as disorientation, visual disturbances, and motor issues, potentially linked to structural and electrophysiological brain changes. To investigate this, electroencephalography (EEG) is a reliable tool to study brain activity in space, measuring oscillatory activity and functional connectivity (FC). This study analyzed EEG data from five male astronauts during three stages: pre-flight, during low Earth orbit (LEO), and post-flight in a 2-min task-free eyes-closed (EC) condition followed by another 2-min of eyes-open (EO) condition. The focus was on beta band (12-30 Hz) activity, which is associated with motor control and proprioception. Results showed increased beta power during spaceflight when compared to pre-flight (EC: p < 0.01) and post-flight (EC: p < 0.01; EO: p < 0.05) conditions. FC strength also increased during spaceflight when compared to pre-flight (EO: p < 0.05) and post-flight (EC: p < 0.01; EO: p < 0.01) conditions. These differences were found primarily in the sensorimotor cortex (SMC) and frontotemporal regions, suggesting the brain's adaptation to altered vestibular and proprioceptive inputs during microgravity. As these results reflect astronaut's movement adaptation to microgravity, this study highlights the importance of understanding central nervous system (CNS) changes during spaceflights to ensure optimal performance and protect astronaut's health during long-duration missions.

Keywords: Beta activity; Brain; EEG; Spaceflight.

Fig. 1

Changes in beta band relative power (eyes-closed) between flight conditions. (a) Statistical comparison between conditions. The bar graph depicts the mean ± SD of the beta band power for each flight condition (*p < 0.05, **p < 0.01, ***p < 0.001). (b–d) Brain figures in the dashed boxes represent the areas with higher statistical power changes in the beta band comparing areas between (b) pre-flight versus in-flight conditions, (c) post-flight versus in-flight conditions, (d) pre-flight versus post-flight conditions. The colorbar is displayed as a family-wise corrected significance level of q value > 5, corresponding with a minimum p value of 0.05. The q statistic value was obtained from the results of the post-hoc Tuckey test of the multiple comparison corrections. Thus, the darker the blue color represents brain regions with higher statistical power. The five subjects are mentioned by the respective code letter under each bar. Brain figures were generated using ‘Image Processing Toolbox’ and ‘Medical Imaging Toolbox’ from Matlab R2023b (version 23.2, https://www.mathworks.com/products/matlab.html).

Fig. 2

Changes in beta band relative power (eyes-open) between flight conditions. (a) Statistical comparison between conditions. The bar graph depicts the mean ± SD of the beta band power for each flight condition (*p < 0.05, **p < 0.01, ***p < 0.001). (b–d) Brain figures in the dashed boxes represent the areas with higher statistical power changes in the beta band comparing areas between (b) pre-flight versus in-flight conditions, (c) post-flight versus in-flight conditions, (d) pre-flight versus post-flight conditions. The colorbar is displayed as a family-wise corrected significance level of q value > 5, corresponding with a minimum p value of 0.05. The q statistic value was obtained from the results of the post-hoc Tuckey test of the multiple comparison corrections. Thus, the darker the blue color represents brain regions with higher statistical power. The five subjects are mentioned by the respective code letter under each bar. Brain figures were generated using ‘Image Processing Toolbox’ and ‘Medical Imaging Toolbox’ from Matlab R2023b (version 23.2, https://www.mathworks.com/products/matlab.html).

Fig. 3

Differences between eyes-closed and eyes-open in beta band relative power between flight conditions. (a) Comparison between eyes-closed and eyes-open in the pre-flight condition (p = 0.1184). (b) Comparison between eyes-closed and eyes-open in the in-flight condition (p = 0.3495). (c) Comparison between eyes-closed and eyes-open in the post-flight condition (p < 0.0001). Bar graphs depict the mean ± SD of the beta band power for each flight condition per subject. The dark blue in a bar indicates the eyes-closed condition, whereas the light blue bar indicates eyes-open condition. The five subjects are mentioned by their respective code letter under each bar. (*p < 0.05, **p < 0.01, ***p < 0.001).

Fig. 4

Changes in beta FC strength (eyes-closed) between flight conditions. (a) Statistical comparison between conditions. The bar graph depicts the mean ± SD of the beta band FC strength for each flight condition (*p < 0.05, **p < 0.01, ***p < 0.001). (b–d) Brain figures in the dashed boxes represent the areas with higher statistical FC changes in the beta band comparing areas between (b) pre-flight versus in-flight conditions, (c) post-flight versus in-flight conditions, (d) pre-flight versus post-flight conditions. The colorbar is displayed as a family-wise corrected significance level of q value > 5, corresponding with a minimum p value of 0.05. The q statistic value was obtained from the results of the post-hoc Tuckey test of the multiple comparison corrections. Thus, the darker the red color represents brain regions with higher statistical power. The five subjects are mentioned by the respective code letter under each bar. Brain figures were generated using ‘Image Processing Toolbox’ and ‘Medical Imaging Toolbox’ from Matlab R2023b (version 23.2, https://www.mathworks.com/products/matlab.html).

Fig. 5

Changes in beta FC strength (eyes-open) between flight conditions. (a) Statistical comparison between conditions. The bar graph depicts the mean ± SD of the beta band FC strength for each flight condition (*p < 0.05, **p < 0.01, ***p < 0.001). (b–d) Brain figures in the dashed boxes represent the areas with higher statistical FC changes in the beta band comparing areas between (b) pre-flight versus in-flight conditions, (c) post-flight versus in-flight conditions, (d) pre-flight versus post-flight conditions. The colorbar is displayed as a family-wise corrected significance level of q value > 5, corresponding with a minimum p value of 0.05. The q statistic value was obtained from the results of the post-hoc Tuckey test of the multiple comparison corrections. Thus, the darker the red color represents brain regions with higher statistical power. The five subjects are mentioned by the respective code letter under each bar. Brain figures were generated using ‘Image Processing Toolbox’ and ‘Medical Imaging Toolbox’ from Matlab R2023b (version 23.2, https://www.mathworks.com/products/matlab.html).

Fig. 6

Differences between eyes-closed and eyes-open in beta band FC strength between flight conditions. (a) Comparison between eyes-closed and eyes-open in the pre-flight condition (p < 0.05). (b) Comparison between eyes-closed and eyes-open in the in-flight condition (p < 0.05). (c) Comparison between eyes-closed and eyes-open in the post-flight condition (p < 0.001). Bar graphs depict the mean ± SD of the beta band power for each flight condition per subject. The dark blue in a bar indicates the eyes-closed condition, whereas the light blue bar indicates eyes-open condition. The five subjects are mentioned by their respective code letter under each bar (*p < 0.05, **p < 0.01, ***p < 0.001).