Neurogenesis in the Adult Brain

National Institute Of Mental Health

Investigators

Linked publications, trials & patents

Abstract

This project focuses on understanding the function of adult neurogenesis in the hippocampal region of the brain. We are interested in understanding how experiences, including positive and stressful experiences, regulate adult neurogenesis and how the new neurons alter behavior in different situations. We study the regulation and function of adult neurogenesis in rats and mice, which show continued production of new neurons throughout adulthood similar to that in primates, including humans. We have previously found that suppression of new neurons in adult mice alters their behavior in several stressful situations. Recently, we investigated the effect of new neurons during social threat. Aggressive behavior is observed in virtually all species and important for optimizing survival and fitness in competitive environments. However, aggression can also cause be damaging physically or to social status, so social interactions must be carefully navigated to produce the appropriate aggressive or affiliative behaviors. We found that mice with suppressed neurogenesis are much less aggressive than normal mice toward similar size males but show normal aggression toward smaller male mice. We found that loss of adult neurogenesis had no effect on sociability or memory for specific individuals when fighting was prohibited. Taken together, these findings show that adult hippocampal neurogenesis plays an important role in the instigation of intermale aggression, likely by biasing a cost–benefit analysis against confrontation in cases where the outcome of the fight is not clear. We have previously seen that rats lacking new neurons show less exploration of novel objects than control mice many weeks after experiencing a stressful experience. Decreased novel object exploration like this has often been interpreted as impaired memory for the previously explored item. However, we have recently found several published data sets in which stress or other experimental manipulations cause mice or rats to exhibit a strong preference for familiar objects over novel objects. Expression of any preference, including one opposite to that normally seen in control animals, requires that animals recall the previously observed item, meaning that this change in behavior cannot be due to memory impairment and must instead reflect a shift in their preference. We believe that preference for novelty in rodents, as in humans, is an expression of curiosity, which is adaptive in high resource, low threat environments but is suppressed following a stress that signals a negative change in the environment.