Spaceflight exposes astronauts to unique microgravity conditions, radiation and altered circadian rhythms, 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.

Here we explore neurophysiological changes in response to microgravity by comparing electroencephalography (EEG) data from two sources: a ground analog head-down tilt bed rest (HDBR) experiment on Earth, and the NEUROSPAT experiment conducted in space. HDBR is commonly used to simulate some physiological effects of microgravity, offering a controlled environment (-6° supine posture) for studying changes similar to those experienced during space travel. The primary objective was to determine whether HDBR could effectively model spaceflight’s impact on the human brain’s EEG signals.

In the HDBR dataset, increases in delta (2 - 4 Hz) (p < 0.01) and theta (4 - 8 Hz) (p < 0.001) power bands were observed during the HDBR condition, predominantly in the left temporal and parieto-occipital regions. Conversely, the NEUROSPAT dataset showed a significant increase in beta (12 - 30 Hz) (p < 0.05) power and in the left somatosensory cortex during in-flight conditions, suggesting a potential adaptation to disrupted proprioceptive input and motor control in microgravity.

The contrasting findings between the two datasets indicate that while HDBR can simulate some aspects of microgravity, it may not serve as a model for all central nervous system changes, especially those related to proprioception and motor functions. These findings contribute to refining Earth-based models and developing countermeasures for space missions.