The memory master’s brain

This is part of a series exploring the brains behind exceptional memory: to what extent is it natural and learnt? How fast can a complete novice pick up a mnemonic? Can memory training help those suffering from memory impairment and depression? Finally, what's going on in the brain as one masters the method of loci?

From the enduring myth of photographic memory to overdramatized depictions of memory palaces on TV, it’s clear that we humans are fascinated with superior memory. Despite its popular appeal throughout history, research on exceptional memory has remained on the fringe – one for the lack of tools, another for the dearth of memory experts to study, and finally for a lack of incentive. After all, how much can we infer about our own memory capabilities by studying those of the masters'?

In fact, a surprising amount.

In 2002, a team of neuroscientists from the UK set out to identify the neurobiological basis of superior human memory. Lucky for them, memory masters were easy to find: every year London holds the World Memory Championships, in which participants from all over the globe, regardless of background and education, go and perform exceptional feats of memory. In all, researchers invited 10 superior memorizers and 10 matched controls to participate in a brain-scanning experiment. On average, the memory masters had practiced mnemonics for over 11 years, but general tests of intelligence showed they scored on a similar level as their controls.

Using structural MRI, researchers found their first unexpected result: the grey matter volume of memory experts was no different than the average Joe, suggesting little structural plasticity had occurred in these people even with years of actively challenging their superior memories. This is in stark contrast with the London cabby study, which found an increase in the size of the drivers' hippocampi as they learned to navigate the entire layout of the 25,000 streets in London.

Perhaps it’s not how big that matters, but how you use it? Researchers next scanned the participant’s brains as they attempted to memorize 6-item lists containing 3 random numbers, faces or snowflakes. They chose these categories for one simple reason: to understand if brain activation patterns represent the amount of information encoded (which is not the main point of the study) or the actual cognitive process underlying encoding. Since superior memorizers particularly excel at learning numbers, somewhat at remembering faces, and not so much snowflakes – the latter being unusual and hard to verbalize – they should remember less across the categories. This was exactly the case.

However, regardless of performance, three brain areas were always active in the memory masters but not the controls: the left medial superior parietal gyrus, bilateral retrosplenial cortex and right posterior hippocampus. These brain areas are all associated with spatial navigation, something seemingly unrelated to memory. A subsequent interview revealed that all but one employed the same ancient technique: the "memory palace", or method-of-loci, which relies heavily on spatial visualization. In the method, each to-be-remembered object is placed along a well-known route through which the individual mentally walks. To retrieve a memory, the person only has to retrace his or her steps.

This study was the first to hint at a tantalizing idea: that memory masters simply make better use of the memory capacities we all share, and that with training, anyone may be able to perform incredible feats of memory. However, this seminal study had a problem: the fMRI differences may simply be due to some mental quirk that the memory masters all possessed, rather than a reflection of their use of the method-of-loci. To nail down the conclusion, researchers would have to train a control group on the method, and see if and how their brain activation patterns change with its use.

Lucky for us, that’s exactly what a team of Swedish researchers did a year later.

The invention of the method of loci (MoL)

According to the Roman orator Cicero, the method of loci was first used by the Greek poet Simonides, who one day was reciting at a banquet. Halfway through his performance, two men – said to be the mythical heroes Castor and Pollux – called him outside for an impromptu meeting. As they conversed, the roof of the building suddenly collapsed, killing everyone present and rendering their bodies unrecognizable. In a bout of inspiration, Simonides mentally journeyed through the building and recalled where each guest had been sitting, thus identifying the dead and allowing their proper burial. Despite its name (loci, Latin for locations), the method has two key elements: navigating an imaginary route, and associating to-be-remembered objects with unusual, absurd and/or emotional images.

Since its inception, the method of loci has been widely adopted in various forms throughout history and has had significant impacts on Western intellectual tradition. In the Middle Ages and Renaissance, the method was further elaborated by the use of highly complex fictitious spaces learned specifically for the purpose of memory storage. Complex systems of predetermined symbolic images litter these “memory palaces”, often with occult or spiritual meanings – no doubt to help with memory storage.

In the present day, method of loci is still widely used by memory masters with little modification to its original form, attesting to its effectiveness. Contrary to popular belief, the method isn’t hard to learn: in fact, as you’ll see in a later post, it may only take 5 minutes.

Maguire EA, Valentine ER, Wilding JM, & Kapur N (2003). Routes to remembering: the brains behind superior memory. Nature neuroscience, 6 (1), 90-5 PMID: 12483214