RESUMEN
Adult animals continue to modify their behavior throughout life, a process that is highly influenced by past experiences. To shape behavior, specific mechanisms of neural plasticity to learn, remember, and recall information are required. One of the most robust examples of adult plasticity in the brain occurs in the dentate gyrus (DG) of the hippocampus, through the process of adult neurogenesis. Adult neurogenesis is strongly upregulated by external factors such as voluntary wheel running (RUN) and environmental enrichment (EE); however, the functional differences between these two factors remain unclear. Although both manipulations result in increased neurogenesis, RUN dramatically increases the proliferation of newborn cells and EE promotes their survival. We hypothesize that the method by which these newborn neurons are induced influences their functional role. Furthermore, we examine how EE-induced neurons may be primed to encode and recognize features of novel environments due to their previous enrichment experience. Here, we gave mice a challenging contextual fear-conditioning (FC) procedure to tease out the behavioral differences between RUN-induced neurogenesis and EE-induced neurogenesis. Despite the robust increases in neurogenesis seen in the RUN mice, we found that only EE mice were able to discriminate between similar contexts in this task, indicating that EE mice might use a different cognitive strategy when processing contextual information. Furthermore, we showed that this improvement was dependent on EE-induced neurogenesis, suggesting a fundamental functional difference between RUN-induced neurogenesis and EE-induced neurogenesis.
Asunto(s)
Discriminación en Psicología/fisiología , Ambiente , Discapacidades para el Aprendizaje/etiología , Discapacidades para el Aprendizaje/rehabilitación , Choque/complicaciones , Animales , Condicionamiento Psicológico/fisiología , Condicionamiento Psicológico/efectos de la radiación , Irradiación Craneana , Discriminación en Psicología/efectos de los fármacos , Miedo/fisiología , Femenino , Hipocampo/patología , Hipocampo/efectos de la radiación , Discapacidades para el Aprendizaje/patología , Ratones , Ratones Endogámicos C57BL , Actividad Motora/fisiología , Actividad Motora/efectos de la radiación , Neurogénesis , Neuronas/metabolismoRESUMEN
In this study, we determined the contribution of juvenile neurogenesis to the performance of mice on a remote memory for temporally based association task and in a novelty based spatial pattern separation task. This was accomplished by mating homozygous DNMT1-loxP mice with heterozygous GFAP-Cre mice and comparing Cre+ (no postnatal neurogenesis) to Cre- (wild type) littermate offspring. The results indicate that Cre+ mice are impaired relative to Cre- mice in the remote memory for a temporal based association task and in a novelty based spatial pattern separation task. These results support the temporal integration model of Aimone et al., [(2006) Nat Neurosci 9:723-727] and provide further support for an important role for postnatally born neurons in spatial pattern separation. In contrast, Cre+ mice are not impaired relative to Cre- mice in an object-context recognition task and a spatial location recognition task. These latter data suggest that postnatally derived neurons in the dentate gyrus (DG) do not support all spatial and object recognition functions of the DG.