Neurogenesis in adulthood: a possible role in learning

The role of the hippocampal formation in learning and memory has long been recognized. However, despite decades of intensive research, the neurobiolog ical basis of this process in the hippocampus remains enigmatic, Over 30 ye ars ago, the production of new neurons was found to occur in the brains of adult rodents. More recently, the documentation of adult neurogenesis in th e hippocampal formation of a variety of mammals, including humans, has sugg ested a novel approach towards understanding the biological bases of hippoc ampal function. Contemporary theories of hippocampal function include an im portant role for this brain region in associative learning. The addition of new neurons and consequently. their novel contribution to hippocampal circ uitry could conceivably be a mechanism for relating spatially or temporally disparate events. In this review, we examine several lines of evidence sug gesting that adult-generated neurons are involved in hippocampal-dependent learning. In particular, we examine the variables that modulate hippocampal neurogenesis in adulthood and their relation to learning and memory.