UC San Diego

The process of pattern separation is essential for a more accurate encoding of memories so that newly encoded information would not overwrite similar previously stored information. The dentate gyrus (DG) of the mammalian hippocampus, a highly plastic region with adult neurogenesis, has been long suggested to play a critical role in this process. Adult-born granule cell neurons integrate into the pre-existing network throughout life, and are known to exhibit high plasticity. As a result, this population has been proposed to function in pattern separation by expanding the capacity for plasticity in the DG. The primary aim of this study is to test this hypothesis by testing if adult-born neurons in the DG are necessary to perform a spatial discrimination task, which had previously been shown to be dentate dependent. A GFAP- TK transgenic rat model was used, in which neurogenesis could be ablated with the administration of the drug valganciclovir. This was corroborated through doublecortin immunohistochemistry (98 ± 0.5% reduction in GFAP-TK animals with drug administration in comparison to controls). These animals were compared to two control groups: wildtype animals with drug administration and GFAP -TK animals without drug administration. This study also involved dorsal DG (dDG) lesioned animals to confirm the task was dentate dependent in the conditions under which this study was conducted. Results show similar performance between animals with and without intact NG, suggesting that the ablation of immature neurons from the DG does not produce disruptions in place learning for spatial locations