Astronauts on interplanetary missions - such as to Mars - will be exposed to space radiation, a spectrum of highly-charged, fast-moving particles that includes 56Fe and 28Si. Earth-based preclinical studies show space radiation decreases rodent performance in low- and some high-level cognitive tasks. Given astronaut use of touchscreen platforms during training and space flight and given the ability of rodent touchscreen tasks to assess functional integrity of brain circuits and multiple cognitive domains in a non-aversive way, here we exposed 6-month-old C57BL/6J male mice to whole-body space radiation and subsequently assessed them on a touchscreen battery. Relative to Sham treatment, 56Fe irradiation did not overtly change performance on tasks of visual discrimination, reversal learning, rule-based, or object-spatial paired associates learning, suggesting preserved functional integrity of supporting brain circuits. Surprisingly, 56Fe irradiation improved performance on a dentate gyrus-reliant pattern separation task; irradiated mice learned faster and were more accurate than controls. Improved pattern separation performance did not appear to be touchscreen-, radiation particle-, or neurogenesis-dependent, as 56Fe and 28Si irradiation led to faster context discrimination in a non-touchscreen task and 56Fe decreased new dentate gyrus neurons relative to Sham. These data urge revisitation of the broadly-held view that space radiation is detrimental to cognition.
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Research supported by NASA grants NNX07AP84G (to BPC and AJE), NNX12AB55G (to AJE and BPC), and NNX15AE09G (to AJE) and NIH grants to AJE DA007290, DA023555, and DA016765. CWW was supported by an NIH Institutional Training grant (DA007290, PI: AJE, David W. Self), and SY was supported by an NIH Institutional Training Grant (MH076690, PI: CA Tamminga), a PENN McCabe award, an 2019 IBRO travel grant and NARSAD Young Investigator Grant from the Brain and Behavior Research Foundation.
Whoolery, Cody W.; Yun, Sanghee; Reynolds, Ryan P.; Lucero, Melanie J.; Soler, Ivan; Tran, Fionya H.; Ito, Naoki; Redfield, Rachel L.; Richardson, Devon R.; Shih, Hung-Ying; Rivera, Phillip D.; Chen, Benjamin P. C.; Birnbaum, Shari G.; Stowe, Ann M.; and Eisch, Amelia J., "Multi-Domain Cognitive Assessment of Male Mice Shows Space Radiation Is Not Harmful to High-Level Cognition and Actually Improves Pattern Separation" (2020). Neurology Faculty Publications. 50.