Effects of Low Dose Exposure to Radiation and Sleep Fragmentation on Discrimination in String-Pulling Behavior with Female Rats

Astronauts will face harmful stressors, such as galactic cosmic radiation (GCR) and sleep fragmentation (SF), on a three-year space flight mission to Mars and back. Astronauts perform skilled reach-to-grasp behaviors on these missions, including interacting with controls to navigate the spacecraft. Recent work has shown that GCR and SF disrupt skilled reach-to-grasp behavior in rodent models; however, the underlying nature of these deficits is unknown. To determine if tactile sensation and proprioceptive feedback contribute to these impairments, this study evaluated the effects of radiation and SF exposure on memory and sensorimotor discrimination in a rodent model. Twenty-one outbred Wistar, retired breeder, female rats were food restricted, habituated in a string-pulling task to a single thick (0.2 cm diameter, 162 cm length) string, and then half were irradiated with 10 centi-grays of 250 MeV/n Helium (single ion in GCR). After irradiation, rats were reassessed with a single thick string and then tested with side-by-side thick and thin strings (0.1 cm) pre- and post-SF (12h session where a mechanical bar swept across the floor every two minutes). Thus far, findings show that rats took significantly fewer trials to reach criterion after one session of SF regardless of radiation status; one session of SF and irradiation did not impair memory in a simple discrimination task using string-pulling behavior which may be attributed to practice effects. Ongoing analyses of cognitive and fine motor skill performance measures may contribute to understanding spared versus impaired performance aspects after SF and when irradiated.