Neurophysiological and Cognitive Changes Induced by the Acute Head-Down Tilt

Introduction: In space, under weightlessness conditions, human brain activity is changed due to the shifting of body fluid and blood toward the cephalic region. This shifting leads to changes in cerebral hemodynamics and, consequently, neurophysiological function, which impacts mental functions like cognition and decision-making capabilities of space travelers. The present study reports the effect of acute exposure to simulated microgravity on cognitive functions and event-related potentials.

Methods: There were 18 healthy human subjects who participated in a 1-h 6° head-down tilt (HDT) bed rest to simulate physiological conditions during microgravity. Subjects were instructed to perform event-related potential tasks and cognitive tasks with a simulator sickness questionnaire to evaluate their performance, attention, and alertness during weightlessness, at baseline, after microgravity exposure, and after a recovery of 30 min.

Results: A significant change was found in the latency of P300 as compared to the baseline. The amplitude of the P300 wave was changed during HDT. The mean reaction time of contingent negative variation increased significantly as compared to the baseline. A significant increase in choice reaction time was observed during HDT vs. baseline. The values recovered partially after 30 min of exposure.

Discussion: It was concluded that simulated microgravity impacts mental functions as evidenced by alterations in choice reaction time and event-related potential latencies and reaction time. The study has applied value for understanding neurophysiological responses and optimization of cognitive performance in space conditions. Sharma M, Gaur S, Pawar H, Yadav N, Thondala B, Kumar S, Kishore K, Ray K, Panjwani U. Neurophysiological and cognitive changes induced by the acute head-down tilt. Aerosp Med Hum Perform. 2025; 96(1):45-52.