To investigate the function(s) of adult hippocampal neurogenesis, behavioral testing with two different animal models was conducted. The first model utilised transgenic mice expressing a Wnt signalling inhibitor (dnWNT) in the DG to knock-down neurogenesis in vivo and was used to analyse the contribution of neurogenesis to pattern separation or pattern completion. We found that these mice were unable to discriminate highly similar patterns, which implies that newborn neurons are involved in pattern separation rather than pattern completion as implicated by theoretical models. The second model was the R6/2 mice which recapitulate the features of Huntington's disease. Environmental enrichment (EE) was used before testing to partially rescue neurogenesis in these mice. We did not observe any positive effect of EE. Instead, enriched mice had a worse performance in some tasks. These finding suggest that enrichment can have different, and in some cases, opposite effects on performance in learning tasks