Pharmacological modulation of stress reactivity dissociates general learning ability from the propensity for exploration

It has previously been reported that general learning ability (GLA) correlates positively with exploratory tendencies in individual outbred mice. This finding suggests the possibility that variations in stress reactivity modulate GLA and thus its relationship to exploratory tendencies. Here, the authors investigated the potential role of stress reactivity in regulating this relationship by assessing the effects of the anxiolytic chlorodiazepoxide (CDP; 10 mg/kg) on subjects' performance in a battery of diverse learning tasks as well as exploratory behaviors and stress reactivity. CDP-treated mice exhibited reductions in stress-induced corticosterone levels and behavioral reactivity to mild stressors and a corresponding increase in exploration. However, CDP-treated mice did not exhibit facilitated acquisition of any of the learning tasks and expressed GLA comparable to controls. Results indicate that although reduced stress reactivity promotes exploration, this does not translate into an up-regulation of GLA, suggesting that the relationship between GLA and exploration is not mediated by stress reactivity. The authors propose that variations in GLA reflect individuals' propensity for novelty seeking, whereas exploration reflects both stress reactivity and novelty seeking, the latter of which may underlie the relationship between exploration and GLA.