Check out the variation in patterns of brain activation among test subjects trying to recall items from a previously displayed word list. The best performer was S.C., and this subject also had the most intense activation and reproducibility in her testing 5 months later. The blue arrows indicate the right parietal area (imagery, attention), whereas the green arrows indicate more conventional prefrontal working memory areas.
We've included a snapshot from "musical imagery" in pianists for comparison. The last link below is a paper which shows that the parietal and prefrontal areas can be strengthened (and the fMRI signals more activated) with memory training involving mneumonics.
Individual Differences in Retrieval fmri pdf
Working Memory Training fMRI pdf