The Posterior Dominant Rhythm Remains Within Normal Limits in the Microgravity Environment

Area of Science:

• Neuroscience
• Space Physiology
• Biomedical Engineering

Background:

• Electroencephalogram (EEG) biomarkers are vital for monitoring astronaut brain health during space missions.
• Assessing changes in EEG patterns, specifically the posterior dominant rhythm (PDR), under microgravity is crucial for understanding neurophysiological adaptations.
• Developing sensitive and specific EEG biomarkers is essential for ensuring crew safety and mission success.

Purpose of the Study:

• To evaluate alterations in the posterior dominant rhythm (PDR) spectral features of the electroencephalogram (EEG) in astronauts during a space mission.
• To compare in-flight EEG recordings with pre- and post-mission terrestrial recordings to detect microgravity effects.
• To determine the stability of basic PDR characteristics under short-term microgravity exposure.

Main Methods:

• Utilized dry-electrode EEG headgear for self-donned recordings on three crew members during the 16-day AXIOM-1 mission.
• Recorded resting-state EEG with eyes open and closed, focusing on PDR oscillations during eye closure.
• Analyzed PDR waveform averaging and time-frequency characteristics using cursor-based peak identification.

Main Results:

• No statistically significant differences were observed in the mean frequency of the PDR between in-flight and ground-based EEG recordings.
• The standard deviation for PDR oscillations remained within a ±1Hz range across all conditions and subjects.
• Power spectral density of the PDR also showed no significant variations between space and terrestrial recordings.

Conclusions:

• The spectral characteristics of the posterior dominant rhythm (PDR) remain stable within normal physiological limits during short-duration space missions.
• A ±1 Hz variation in PDR frequency is considered acceptable and does not indicate significant neurophysiological changes due to microgravity.
• Further research is needed to identify other EEG features that may reflect human brain neurophysiology during extended space exploration.