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. Impaired CD performance would result in a decreased ability to identify and focus on relevant aspects of a task being conducted, while the functional consequence of an impaired CDR performance would be a reduction in the individual's ability to recognize when that factor changes from a positive to a negative factor for the successful completion of a task. In contrast to our previous study with 1 GeV/n (56)Fe particles, there were no significant impairments in the ability of the (48)Ti-irradiated rats to conduct simple discrimination. This study further supports the notion that "mission-relevant" doses of HZE particles (<20 cGy) can impair certain aspects of attentional set-shifting performance in retired breeder rats, but there may be some ion-specific changes in the specific cognitive domains impaired.