M. L. Jacobson1, R. Clouse2, M. Kim2, B. Carney1, D. Kim1, P. S. Coburn-Litvak2, B. J. Anderson1
1Psychology and Integrative Neurosci., Stony Brook Univ., Stony Brook, NY; 2Biol., Andrew Univ., Berrien Springs, MI
Adaptation to chronic unpredictable threat yields resilience under testing conditions that match previous exposure to threat*
Stressors experienced in day-to-day life may yield responses that are adaptive in matched environments and maladaptive in mismatched environments. To help understand adaptations in different contexts, our lab has designed a rodent living environment that allows manipulation of threat prediction and control. When presenting repeatable unpredictable threat (UT) without harm, we have previously found impairments in spatial working memory. In contrast, UT rats had enhanced responses to aversive stimuli (defensive burying and acoustic startle response). This pattern led us to hypothesize (H1) that UT rats have adapted to perform optimally under high stress conditions, but at a cost to performance in low stress conditions (such as our memory task). Alternatively, hypothesis 2 (H2) predicts UT rats have prioritized behaviors that are rapid and hard-wired, and at the expense of time-intensive strategic behaviors. To test these hypotheses, we re-examined working memory in the Barnes maze, this time under high stress conditions. H1 predicts that UT rats should perform equal to or better than controls, whereas H2 predicts that the testing environment will have no effect, and UT rats will continue to be impaired relative to controls. Rats were housed with resources (food and water) separated by a tunnel for three weeks. Simultaneous presentations of predator odor, abrupt lights and sound, were presented randomly (p=.25) in the center of the tunnel during crossings in the UT condition, whereas control (CT) rats crossed without risk. After the condition, animals were tested in the Barnes maze, which was conducted in a brightly lit room, and with the addition of distracting and novel extra-maze stimuli. Pilot data suggest that the threat group outperforms the control group in aversive test conditions. A subset of CT rats were at first dysfunctional and unable to complete the task. When only functioning animals were compared across groups, threat animals performed at the level of control animals. The data are inconsistent with hypothesis 2, which states that some behaviors are prioritized over others, and therefore UT animals will be impaired on the tests of spatial learning regardless of test conditions. Instead, UT rats performed better or equal to CT rats in aversive test conditions, which supports hypothesis 1. The findings suggest that adaptations shape behaviors broadly for optimal performance in environments that match the previously experienced environment. The pattern of results parallel the match/mismatch hypothesis, suggesting generalization of that concept to behavioral adaptations at later stages of development.
*Students Rebecca Clouse and Mikyung Kim, along with Biology Professor Dr. Pamela Coburn-Litvak, presented the above research at the Society for Neuroscience in November of 2013.