New nerve cell growth in stress-induced social avoidance.

Lagace et al. look at changes in the dentate gyrus region of the hippocampus to probe why some people are resilient to long-term chronic stress while others develop maladaptive functioning. They examined chronic social defeat stress in a mouse model, finding that synthesis of new nerve cells is increased after social defeat stress selectively in mice that display persistent social avoidance. Irradiation that halts formation of these new nerve cells inhibits appearance of social avoidance, suggesting a functional role for adult-generated dentate gyrus neurons. The data show that the time window after cessation of stress is a critical period for the establishment of persistent cellular and behavioral responses to stress and that a compensatory enhancement in neurogenesis is related to the long-term individual differences in maladaptive responses to stress.