Personality, Performance, and Corticosterone in White-Footed Mice

AbstractPrevious small rodent studies report a negative correlation between exploration and locomotor performance. In other words, individuals that are more exploratory during a novel environment test run more slowly on a racetrack during a forced-exercise test. Given that measuring both exploration and sprint speed involves stress (novelty, open space, stimuli to prompt running), glucocorticoid hormones may play a role in the negative exploration-speed relationship. We repeatedly measured exploration, sprint speed, and blood corticosterone levels in 51 captive female white-footed mice. As in prior rodent studies, exploration and sprint speed were negatively correlated at the among-individual level. Moreover, contrasting relationships were obtained between corticosterone and exploration (baseline corticosterone, $r=-0.523$; postexercise corticosterone, r = -0.290) and between corticosterone and sprint speed (baseline corticosterone, $r=0.306$; postexercise corticosterone, r = 0.400). Accordingly, the exploration-sprint speed correlation was halved (from $r_{\mathrm{ind}}=-0.272$ to r_ind = -0.129) when conditioning on both baseline and postexercise corticosterone (measured 3 min after the forced-exercise tests). Considering the overall strength and direction of the associations between baseline versus postexercise corticosterone and behavior versus performance, our results support the hypothesis that glucocorticoid stress hormones play a role in the observed negative relationship between exploration and locomotor performance.