A Two-Hit Model of Executive Dysfunction: Simulated Galactic Cosmic Radiation Primes Latent Deficits Revealed by...

Area of Science:

• Neuroscience
• Space Biology
• Cognitive Science

Background:

• Future Mars missions pose risks to astronaut cognitive function due to prolonged space radiation (SR) and sleep disruption (SF).
• Independent effects of SR and SF on cognition are known, but their combined impact is poorly understood.
• Cognitive functions like decision-making and executive function are critical for mission success and astronaut autonomy.

Purpose of the Study:

• To investigate the combined effects of space radiation simulation and sleep fragmentation on cognitive performance in a rodent model.
• To determine if SR primes the brain for cognitive deficits when subsequently exposed to SF.
• To identify potential mechanisms underlying cognitive vulnerabilities in spaceflight.

Main Methods:

• Male rats were exposed to Galactic Cosmic Ray simulation (GCRsim), sleep fragmentation (SF), or both.
• Cognitive performance was assessed using the Associative Recognition Memory and Interference (ARMIT) task.
• Performance was analyzed under well-rested conditions and after a single night of SF.

Main Results:

• GCRsim exposure alone caused deficits in cognitive flexibility, particularly when reinforcement contingencies shifted.
• Rats exposed to both GCRsim and SF exhibited latent deficits after SF, performing poorly on tasks requiring attentional control and decision updating.
• These deficits manifested as perseverative errors, indicating impaired ability to adapt to changing feedback.

Conclusions:

• Space radiation may prime neural networks, making them vulnerable to collapse under subsequent sleep disruption, supporting a 'two-hit' model.
• Astronauts may exhibit persistent or stress-induced cognitive deficits, both posing threats to mission success.
• Understanding these vulnerabilities is crucial for developing effective countermeasures for long-duration spaceflight.