Hippocampal Neurogenesis Leads to the Erasure of a Cocaine Conditioned Place Preference

Newborn neurons are generated in the hippocampus during adulthood. Little is known however about the functional role of these new neurons. Previous research proposed that ongoing neurogenesis clears established memories from the hippocampus (Frankland et al., 2013). Consistent with this, we recently found that high rates of neurogenesis induce forgetting of hippocampus-dependent spatial and fear memories (Akers et al., 2014). These tasks were all aversively-motivated. To test whether neurogenesis-mediated forgetting generalizes to appetitively-motivated, hippocampus-dependent memories, here we used a cocaine place preference paradigm. We found that increasing neurogenesis (by voluntary exercise) before training did not impact the acquisition of cocaine place preference. However, increasing hippocampal neurogenesis after training weakened an established cocaine place preference memory. This series of studies provides insight to the temporal impact of neurogenesis and suggests a possible link between exercise and memory functioning.M.A