Issues to ponder when correlating hippocampal neurogenesis to a hippocampal-dependent memory function

Simple correlations between the overall hippocampal neurogenesis and the hippocampal-dependent learning and memory functions are common in the neurogenesis field. There is considerable evidence in the literature to link hippocampal neurogenesis to the hippocampal-dependent memory function. However, simple correlations between neurogenesis and memory function, particularly in studies where neither the cause-effect relationship is established nor the other relevant variables are considered, can lead to erroneous conclusions. As reliable and selective neurogenesis ablation techniques are yet to be developed for rat and higher animal models, it is likely that correlative studies between the overall neurogenesis and the memory function will continue in different conditions in these animal models. Such correlations should be acceptable as long as the other variables are considered adequately. Furthermore, in correlative analyses of the learning and memory function with the newly born granule cells, one needs to consider the age of the newly born granule cells because the newly born granule cells will require at least a few weeks of time after their birth to participate in the learning and memory function in rodent models.