Stress facilitates late reversal learning using a touchscreen-based visual discrimination procedure in male Long Evans rats

Abstract

The stress response is essential to the survival of all species as it maintains internal equilibrium and allows organisms to respond to threats in the environment. Most stress research has focused on the detrimental impacts of stress on cognition and behavior. Reversal learning, which requires a change in response strategy based on one dimension of the stimuli, is one type of behavioral flexibility that is facilitated following some brief stress procedures. The current study investigated a potential mechanism underlying this facilitation by blocking glucocorticoid receptors (GRs) during stress. Thirty-seven male Long Evans rats learned to discriminate between two images on a touchscreen, one of which was rewarded. Once a criterion was reached, rats received stress (30min of restraint stress or no stress) and drug (GR antagonist RU38486 or vehicle) administration prior to each of the first 3 days of reversal learning. We expected that stress would facilitate reversal learning and RU38486 (10mg/kg) would prevent this facilitation in both early (<50% correct in one session) and late (>50% correct in one session) stages of reversal learning. Results showed that stressed rats performed better than unstressed rats (fewer days for late reversal, fewer correction trials, and fewer errors) in the late but not early stage of reversal learning. RU38486 did not block the facilitation of RL by stress, although it dramatically increased response, but not reward, latencies. These results confirm the facilitation of late reversal by stress in a touchscreen-based operant task in rats and further our understanding of how stress affects higher level cognitive functioning and behavior.