The dentate gyrus is a major site of plasticity in the adult brain, giving rise to thousands of new neurons every day. While the majority of these cells die within two weeks of their birth, they can be rescued from death by various forms of learning. The successful acquisition of select types of associative and spatial memories can increase the number of these cells that survive. Here, we investigated the possibility that an entirely different form of learning, physical skill learning, could rescue these new neurons from death. To test this possibility, rats were trained with a physically-demanding and technically-difficult version of a rotarod procedure. Acquisition of the physical skill greatly increased the number of new hippocampal cells that survived. The number of surviving cells positively correlated with performance on the task. Only animals that successfully learned the task retained the cells that would have otherwise died. Animals that failed to learn, and those that did not learn well, did not retain any more cells than those that were untrained. Importantly, acute voluntary exercise in activity wheels did not increase the number of surviving cells. These data indicate that skill learning, and not physical activity per se, increased the number of surviving cells. Moreover, learning an easier version of the task did not increase cell survival. These data are consistent with previous studies revealing that learning rescues new neurons from death, but only when acquisition is sufficiently difficult to achieve. Finally, complete hippocampal lesions did not disrupt acquisition of this physical skill. Therefore, learning this motor skill task does not depend on the hippocampus, even though it can increase the number of surviving cells in the structure. These data, and their implications, suggest that humans who learn new and complicated sports or other physical skills will retain more new neurons than humans that do not engage in effortful activities.Ph. D.Includes bibliographical referencesby Daniel M. Curlik I
