Presentations

Abstract

Introduction: Astronauts on the proposed deep space missions to Mars will be exposed to an estimated ~30 cGy of galactic cosmic radiation (GCR). There are numerous studies that indicate space radiation (SR) impairs cognitive processes, including executive function. However, executive function also regulates inhibition, impulse control, processing and regulating affect, motivation, and arousal. Astronauts on board a mission are routinely assessed using the Balloon Analogue Risk Task (BART), a validated assessment of risk-taking behavior that has demonstrated correlation with baseline risk propensities in humans. While ground-based rodent studies have demonstrated that SR significantly impairs executive function, there is limited research on how SR will impact risk decision making. We hypothesized that SR exposure will impact risk decision making in rodents in addition to the already anticipated psychological stress.

Methods: Female rats previously exposed to a low dose (10 cGy) of either 4He ions or a cocktail of 6 ions that simulates the galactic cosmic ray spectrum (GCRSim) were screened initially on an attentional set shifting (ATSET) task to provide a measure of executive function. In this study, female rats previously screened for ATSET performance were put on a restricted diet and were trained in the Rodent Gambling Task (RGT). The rats underwent a gradual training process, progressing through five training stages (H1-H5), that collectively constitute a Stimulus Response (STR) training procedure. During the STR procedure, rats progressively learn that a food reward is only obtained if they press an illuminated response light within 10 seconds. The rats that met the criteria in the STR training were subsequently put through RGT. This touchscreen-based task is designed to replicate the impulsivity and risk decision making aspect of BART, consisting of four response lights with cues defining a win/loss probability, reward size and loss penalty. Rats were screened for RGT performance by investigators with no knowledge of the rats' ATSET performance status.

Results: The majority of SR-exposed rats screened for GCT performance to date were rats that had maintained high ATSET performers. Not surprisingly, those rats did not exhibit diminished impulsivity in the gambling task. Female rats exposed to a low dose (10 cGy) of 250 MeV/n He particles were observed to have a greater RTP than their sham counterparts. Increased RTP was found to be significantly associated with increased reaction time during the trials.

Conclusion: SR exposure-induced loss of executive function impacts both cognitive flexibility performance (ATSET) and impulsivity and risk taking propensity (RTP) in female rats. Further studies will determine whether male rats are affected in the same manner. These findings suggest that astronauts into deep space missions with similar exposures to SR may be more likely to make risky decisions.