Neurogenesis in the Adult Brain

National Institute Of Mental Health

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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. The hippocampus is thought to play an important role in spatial learning and memory and is known to undergo structural changes leading to overall volume shrinkage in response to stress. Few studies have examined the structural changes in the hippocampus induced by positive experiences or the role of the hippocampus in shifting behavior following these rewarding experiences. We have focused recently on testing the effects of inhibiting adult neurogenesis on a spatial learning task and in future non-spatial tests. In a rewarded maze task, rats lacking neurogenesis learn and perform as well as control rats, indicating that new neurons are not needed for learning or remembering the spatial layout of the maze. However, rats with intact neurogenesis showed increased novelty approach behavior or curiosity following maze learning, while rats without ongoing adult neurogenesis showed no effects of maze training on this behavior. Rats with intact neurogenesis also showed growth of pyramidal neurons in the ventral CA1 region of the hippocampus and prelimbic cortex as well as MRI-detectable increases in the volume of these two regions and activity in the pathway that connects them. Rats without adult neurogenesis showed none of these structural effects. Together, these findings suggest that neurons born in the adult hippocampus are critical for driving structural and activational effects in a ventral CA1 to prelimbic cortical circuit that drives novelty approach in response to positive learning experiences.