Accumulating epidemiological evidence supports the notion of brain reserve, but there has been no investigation of neurobiological change associated with brief mental activation training in humans. Healthy older individuals were therefore investigated with magnetic resonance spectroscopy (MRS) in different brain regions before and after 5 weeks of focused memory training. Recall of a test-word list of > 23 items was achieved accompanied by elevation of creatine and choline signals in the hippocampus. Those at risk for neural dysfunction, as indicated by lower neurometabolites at baseline, demonstrated the largest MRS increases after training. Biochemical changes related to cellular energy and cell-membrane turnover were found to increase after structured memory exercises and were limited to the medial temporal lobe.