Failure to demonstrate that memory improvement is due either to aerobic exercise or increased hippocampal volume.

Abstract

We read with interest the article in PNAS, ?Exercise training increases size of hippocampus and improves memory? by Erickson et al. (1). It is a noteworthy finding that over a 1-y period anterior hippocampal volume increased by 2% in the aerobic exercise group, whereas it decreased by 1.4% in the stretching control group. However, contrary to both the title and abstract, there is virtually no evidence in this article that exercise improved memory.