Examining the ancient technique of "memory palaces" with brain-imaging

A small (51 men aged 24 +/- 3 years) study published in Neuron tasked experimental subjects with practicing the ancient Greek mnemonic technique of "memory palaces" and then scanned their brains with functional magnetic resonance imaging, comparing the scans to scans from competitive "memory athletes" and also measuring their performance on memorization tasks.

Memory palaces are a well-understood technique that is simple to learn, but requires a lot of practice to perfect. In brief, you start with a path through building you know very well (say, your home) and you "place" mnemonic reminders along that path: for example, you might put the first item in the list over the keyhole to your front door, the second hanging from the coathook just inside it, the third on the stairway railing leading upstairs, the fourth on the bottom step, etc. These mnemonics are absurd, memorable juxtapositions, often drawing on a pre-memorized set of associations (you might memorize a different strange object for every number between 0-9, like "0 is a gasping fish" and "1 is a smashed potato" etc and then use those to make the objects in your palace more memorable).

Derren Brown develops the technique well in his lively 2008 book "Tricks of the Mind" and they play a major role in Hannibal Rising, Thomas Harris's 2007 prequel to Silence of the Lambs.

The study seeks to find physical, functional neural correlates to memory training, and it does, though the small sample size -- and even smaller sample of "memory athletes" (23 of them!) calls the enterprise into question. It seems logical that mindful mental practice, repeated intensively for many days, would cause functional reorganization that an fMRI could pick up, but is that the whole story? How much does that reorganization correlate to memory performance? Does it endure?

More interesting is the simple validation for the technique -- which, again, isn't surprising, as the technique is widely endorsed by memory athletes -- because you never know whether these old techniques have hung around because of the appeal to antiquity or because they work.

We investigated 23 memory athletes (aged 28 ± 8.6 years, nine women) of the top 50 of the memory sports world ranking list. We used MRI to assess both brain anatomy and function during task-free rest before engaging in memory tasks. All of these participants attribute their superior memory skills to deliberate training in mnemonic strategies. The memory athletes were compared with a control group closely matched for age, sex, intelligence, and handedness. Of the 23 athletes, 17 participated in a word learning task under fMRI conditions where they demonstrated their superior memory abilities compared to controls (70.8 ± 0.6 versus 39.9 ± 3.6 of 72 words correctly recalled 20 min after encoding; median, 72 versus 41; Wilcoxon signed-rank test, p < 0.001, r = 0.62).

As to whether naive controls can improve their memory with mnemonic training similar to that of memory athletes, 51 participants (aged 24 ± 3.0 years, all men) without any prior experience in mnemonic strategies completed two fMRI sessions over a 6-week interval (Figure 1). In each session, all participants performed a memory test in which they memorized 72 words. Memory was tested with free recall after 20 min and again after 24 hr. After the 24-hr retest of the first session, subjects were pseudo-randomly assigned to 6 weeks (40 × 30 min) of mnemonic training in the method of loci or an active (n-back working memory training) or passive (no training) control condition (Figure 1). At the conclusion of the 6-week training period, participants returned for a post-training assessment that again included a resting state fMRI scan and a further encoding session of 72 new words, followed by free recall after 20-min and 24-hr delays. Then 4 months after training completion, participants of all three groups were invited again for a memory test of the 72 words used in the first session to assess potential long-term benefits of mnemonic training.

Mnemonic Training Reshapes Brain Networks to Support Superior Memory
[Martin Dresler, William R. Shirer, Boris N. Konrad, Nils C.J. Müller, Isabella C. Wagner, Guillén Fernández, Michael Czisch and Michael D. Greicius/Neuron]

Ancient technique can dramatically improve memory, research suggests
[Hannah Devlin/The Guardian]

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