Neurophysiological, neuropsychological, and cognitive effects of 30 days of isolation.

ABSTRACT

The increasing demand of space flights requires a profound knowledge of the chronologic reactions of the human body to extreme conditions. Prior studies already have shown the adverse effects of long-term isolation on psycho-physiological well-being. The chronology of the effects and whether short-term isolation periods already lead to similar effects has not been investigated. Therefore, the aim of the current study was to investigate the effects of short-term isolation (30 days) on mood, cognition, cortisol, neurotrophic factors, and brain activity. 16 participants were isolated in the Human Exploration Research Analog at NASA for 30 days. 17 non-isolated control participants were tested simultaneously. On mission days - 5, 7, 14, 28, and + 5, multiple tests including the Positive and Negative Affect Schedule-X and cognitive tests were conducted, and a 5-min resting electroencephalography was recorded. A fasted morning blood drawing was also done. Increased stress was observed via augmented cortisol levels during the isolation period. Activity within the parietal cortex was reduced over time, probably representing a neural adaptation to less external stimuli. Cognitive performance was not affected, but rather enhanced in both groups. No further significant changes in neurotrophic factors BDNF/IGF-1 and mood could be detected. These results suggest that 30 days of isolation do not have a significant impact on brain activity, neurotrophic factors, cognition, or mood, even though stress levels were significantly increased during isolation. Further studies need to address the question as to what extent increased levels of stress do not affect mental functions during isolation periods.