I believe you are mistaken.

Adult neurogenesis has only been shown to occur in three brain regions as far as I know: in the hippocampus (declarative memory and learning)[1], the olfactory bulb (smell)[1] and the striatum (procedural memory and learning) [2].

Adult hippocampal neurogenesis (AHN) has been linked to exercise. The conceptual leap which requires empirical validation is that exercise induced neurogenesis in the hippocampus indeed has a positive effect on memory. Maybe those experiments exist.

[1] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3106107/ [2] http://www.ncbi.nlm.nih.gov/pubmed/24561062