Executive function in socially-mature rats is significantly impaired by low (<20 cGy) doses of HZE particles with LETs of 51-180 keV/um

INTRODUCTION. Astronauts on deep space missions will be exposed to ~25 cGy of Galactic cosmic radiation (GCR). The long-term consequence of exposure to such doses is largely unknown, but we have previously shown that exposure of juvenile rats to 20 cGy 1 GeV/μ 56 Fe resulted in pronounced deficits in hippocampus-dependent learning (Britten et al, 2012) and Attentional Set shifting (ATSET) (Lonart et al, 2012), a measure of executive function. ATSET can be simplistically thought of as the ability of an individual to relearn what the most important discriminating stimulus is (for a particular endpoint) in a changing environment. ATSET is thus one of the most advanced thought processes that enable humans to rapidly adapt and respond to a change in the environment, and to perceive what is important for survival or completion of a task, skills that are absolutely vital to deal with a sudden emergency. Aged rats have a reduced capacity to conduct various aspects of ATSET compared to younger rats, so it is possible that the effect of HZE exposure in rats of a comparable biological age to the Astronauts may result in further reductions in their ATSET capacity. We have thus assessed the impact that exposure of male Retired Breeder Wistar rats to 10, 15 or 20 cGy of the following ion beams: 600 Mev/μ 56 Fe , 1 GeV/μ 56 Fe, 1.1 GeV/μ 48 Ti or 600 Mev/μ 28 Si (with respective LET values of 180, 150, 106 and 51 keV/um) has on their ability to perform ATSET.