Impaired Spatial Memory Performance in Adult Wistar Rats Exposed to Low (5-20 cGy) Doses of 1 GeV/n (56)Fe Particles

Area of Science:

• Space science
• Neuroscience
• Radiation biology

Background:

• Deep space missions expose astronauts to galactic cosmic radiation, including high-Z and energy (HZE) particles.
• Prior studies indicate HZE particle exposure impairs neurocognitive function, with significant individual variability in response.
• Understanding inter-individual differences is crucial for accurate radiation risk assessment models.

Purpose of the Study:

• To investigate the effects of iron-56 (56Fe) particle radiation on spatial memory in rats.
• To quantify neurocognitive performance changes and inter-individual variations after HZE particle exposure.
• To inform the development of probabilistic risk assessment models for space radiation.

Main Methods:

• 269 male Wistar rats were exposed to 1 GeV/n 56Fe radiation at doses of 0, 5, 10, 15, and 20 cGy.
• Spatial memory was assessed using the Barnes maze three months post-exposure.
• Radiation response was analyzed by comparing mean cohort performance and the proportion of poor responders.

Main Results:

• Acute exposure to mission-relevant 56Fe doses significantly reduced mean spatial memory performance (P < 0.002).
• The proportion of poor performers (defined as >2 SD below sham controls) increased 2- to 3-fold.
• A substantial fraction of irradiated rats showed no detectable performance deficits, irrespective of dose.

Conclusions:

• Space radiation significantly impairs neurocognitive function, specifically spatial memory, in a rodent model.
• Individual susceptibility to radiation-induced neurocognitive impairment varies considerably.
• Personalized metrics are essential for developing robust probabilistic risk assessment models for HZE particle exposure in astronauts.