Exposure to ≤15 cGy of 600 MeV/n Fe Particles Impairs Rule Acquisition but not Long-Term Memory in the Attentional Set-Shifting Assay.

On future missions into deep space, astronauts will be required to work more autonomously than on previous missions, and thus their ability to perform executive functions could be critical to mission success. In this study, we determined the effect that ≤15 cGy of 600 MeV/n Fe particles has on attentional set-shifting (ATSET) performance of ∼10 month-old (at the time of irradiation) male Wistar rats that had been prescreened for their ability to perform the task. Exposure to 1-15 cGy of Fe particles leads to a significant impairment in compound discrimination (CD) performance.

Impaired Attentional Set-Shifting Performance after Exposure to 5 cGy of 600 MeV/n Si Particles.

Astronauts on deep space missions will be required to work more autonomously than on previous missions, and thus their ability to perform executive functions could be critical to mission success. One of the most common measures of executive function in humans is the ability to perform attentional set shifting, which requires contributions from working memory, discrimination, reversal learning, attentional set shifting and attention. Rodent attentional set shifting assays require rats to form an association between the presence of the food reward and an associative cue, which is either the digging media or the scent that is placed in the bowl; by altering the combination of scent and digging media, progressively more complex cognitive processes can be tested.

Quantitative Proteomic Analysis of the Hippocampus of Rats with GCR-Induced Spatial Memory Impairment.

NASA is planning future missions to Mars, which will result in astronauts being exposed to ∼13 cGy/year of galactic cosmic radiation (GCR). Previous ground-based experiments have demonstrated that low (15 cGy) doses of 1 GeV/n Fe ions impair hippocampus-dependent spatial memory in rats. However, some irradiated rats maintain a spatial memory performance comparable to that seen in the sham-irradiated rats, suggesting that some of these animals are able to ameliorate the deleterious effects of the GCR, while others are not.

Changes in the Hippocampal Proteome Associated with Spatial Memory Impairment after Exposure to Low (20 cGy) Doses of 1 GeV/n Fe Radiation.

Exposure to low (∼20 cGy) doses of high-energy charged (HZE) particles, such as 1 GeV/n Fe, results in impaired hippocampal-dependent learning and memory (e.g., novel object recognition and spatial memory) in rodents.

Spatial Memory Performance of Socially Mature Wistar Rats is Impaired after Exposure to Low (5 cGy) Doses of 1 GeV/n Ti Particles.

Prolonged deep space missions to planets and asteroids will expose astronauts to galactic cosmic radiation (GCR), a mixture of low-LET ionizing radiations, high-energy protons and high-Z and energy (HZE) particles. Ground-based experiments are used to determine whether this radiation environment will have an effect on the long-term health of astronauts and their ability to complete various tasks during their mission. Emerging data suggest that mission-relevant HZE doses impair several hippocampus-dependent neurocognitive processes in rodents, but that there is substantial interindividual variation in the severity of neurocognitive impairment, ranging from no observable effects to severe impairment.

Performance in hippocampus- and PFC-dependent cognitive domains are not concomitantly impaired in rats exposed to 20cGy of 1GeV/n (56)Fe particles.

NASA is currently conducting ground based experiments to determine whether the radiation environment that astronauts will encounter on deep space missions will have an impact on their long-term health and their ability to complete the various tasks during the mission. Emerging data suggest that exposure of rodents to mission-relevant HZE radiation doses does result in the impairment of various neurocognitive processes. An essential part of mission planning is a probabilistic risk assessment process that takes into account the likely incidence and severity of a problem.

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

Prolonged deep space missions to planets and asteroids will expose astronauts to galactic cosmic radiation, comprised of low-linear energy transfer (LET) ionizing radiations, high-energy protons and high-Z and energy (HZE) particles, such as (56)Fe nuclei. In prior studies with rodents exposed to HZE particle radiation at doses likely to be encountered during deep space missions (<20 cGy) investigators reported impaired hippocampal-dependent neurocognitive performance and further observed substantial variation among the irradiated animals in neurocognitive impairment, ranging from no observable effects to severe impairment. These findings point to the importance of incorporating quantitative measures of interindividual variations into next generation risk assessment models of radiation risks on neurocognition.

Exposure to Mission-Relevant Doses of 1 GeV/n (48)Ti Particles Impairs Attentional Set-Shifting Performance in Retired Breeder Rats.

Astronauts on deep space missions will be required to work more autonomously than on previous missions, and thus their ability to perform executive functions could be critical to mission success. In this study we have determined the impact that exposure to 10, 15 and 20 cGy of 1 GeV/n (48)Ti particles has on the long-term (three-months post exposure) ability of male retired breeder Wistar rats to perform attentional set shifting. The ability of the rats to conduct compound discrimination reversal (CDR) was significantly impaired at all doses studied, with compound discrimination (CD) being impaired at 10 and 15 cGy.

Exposure to mission relevant doses of 1 GeV/Nucleon (56)Fe particles leads to impairment of attentional set-shifting performance in socially mature rats.

Previous ground-based experiments have shown that cranial irradiation with mission relevant (20 cGy) doses of 1 GeV/nucleon (56)Fe particles leads to a significant impairment in Attentional Set Shifting (ATSET) performance, a measure of executive function, in juvenile Wistar rats. However, the use of head only radiation exposure and the biological age of the rats used in that study may not be pertinent to determine the likelihood that ATSET will be impaired in Astronauts on deep space flights. In this study we have determined the impact that whole-body exposure to 10, 15 and 20 cGy of 1 GeV/nucleon (56)Fe particles had on the ability (at three months post exposure) of socially mature (retired breeder) Wistar rats to conduct the attentional set-shifting paradigm.