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A memory technique invented by the ancient Greeks can make dramatic and long-lasting improvements to a person’s power of recall, according to research that suggests many of us have extensive untapped memory reserves.

After spending six weeks cultivating an internal “memory palace”, people more than doubled the number of words they could retain in a short time period and their performance remained impressive four months later. The technique, which involves conjuring up vivid images of objects in a familiar setting, is credited to the Greek poet Simonides of Ceos, and is a favoured method among so-called memory athletes.

The study also revealed that after just 40 days of training, people’s brain activity shifted to more closely resemble that seen in some of the world’s highest ranked memory champions, suggesting that memory training can alter the brain’s wiring in subtle but powerful ways.

Nils Müller, a neuroscientist at Radboud University and a co-author of Moonwalking with Einstein:, said:

“One of the initial questions was whether memory athletes have very differently wired brains. Do they have an innate gift that just can’t be taught?”

The answer, perhaps surprisingly, was no. Prodigious feats of memory such as recalling hundreds of binary digits or a Sherlock-like ability to put a name to a face are likely to be mostly down to hours of training and using the right mnemonic techniques, the scientists concluded.

A 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?

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.

Boris Konrad, a neuroscientist at the Max Planck Institute of Psychiatry in Munich who co-authored the study, said: “You really walk through a place and then later you visualise the location to place an object there. You’re not just wandering around in your crazy mental palace.”

It also helps for the image to be vivid, bizarre and firmly placed in the location. In the book, the memory expert Ed Cooke suggests remembering an item on a shopping list by imagining “Claudia Schiffer swimming in tub of cottage cheese.”

Konrad, who also happens to be ranked 24th in the World Memory Championships, said the strategy is effective because it maps boring information onto something that the brain has evolved to do extremely well – recall imagery in specific locations.

“You take material that is really hard to remember and transform it into something accessible,” he said. “It does not make your memory capacity bigger; you use a different form of memory that already has a large capacity.”

After 40 days of 30-minute training sessions, the participants who had average memory skills at the start more than doubled their memory capacity, recalling 62 words on average – and four months later, without continued training, they could remember 48 words from a list of 72.

Martin Dresler, also a neuroscientist at Radboud University and the first author, said: “Once you are familiar with these strategies and know how to apply them, you can keep your performance high without much further training.”

The scientists also studied the brains of their participants and, while there were no telltale signs of memory prowess based on anatomy, subtle differences were seen in the background brain activity of the memory athletes and ordinary subjects when they were asked to simply relax and let their minds wander. This kind of “resting state” scan is designed to give a measure of the brain’s connectivity – essentially a measure of how tightly disparate clusters of neurons are wired together.

After training, the background hum of brain activity in the ordinary participants had shifted to more closely match that seen in the champions – and the closer the resemblance, the better the person’s performance was likely to be.

“After training we see massively increased performance on memory tests,” said Dresler. “Not only can you induce a behavioural change, the training also induces similar brain connectivity patterns to those seen in memory athletes.”

“I would speculate that it reflects activity-dependent rewiring,” said Müller.

Konrad believes that “not everyone can become a champion” – even within the trained group some people fared far better than others. “But everyone using the technique can improve quite substantially from the level they’re at,” he added.

Article byTommy Strickland