Fighting depression with a memory palace

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? 

This is my happy place: a dusty old library filled with tomes upon tomes of my favourite books. I can picture myself walking down the aisles, scanning cover after cover, every single book triggering the same glee and excitement I felt as when I read it for the first time.

Thinking back on happy experiences is a proven way to help deal with the lows of life. But for those suffering from Major Depressive Disorder, accessing such memories is incredibly difficult; instead, they tend to ruminate over negative and self-devaluating incidents. Even worse, when they do recall happier times, they are unable to retrieve a positive moment in life to re-experience in their minds. Instead, they focus on the abstract, contemplating the causes, meanings and consequences of memories rather than the pleasure they bring. Without experiencing joy, they can’t benefit from it.

But what if there’s a way to boost their access to positive memories? What is needed is a powerful technique that conjures up memories so vivid that it transports them back to that happy moment in time.

Luckily, such a method exists. The method of loci (MoL) is an ancient mnemonic that relies on mental imagery. It involves constructing imaginary routes – often through a familiar building or a town - and storing to-be-remembered items at attention-grabbing spots (loci) along the route; one only has to retrace his or her steps to retrieve the memory. The more surreal or bizarre you make these images, the better they can help you remember.

These loci form the building blocks of a more permanent mental repository, in which someone can store information that they want easy and repeated access to in future occasions. Dubbed the “memory palace”, these repositories often comprise elaborate and beautiful fictitious locations built solely for the purpose of information storage. The MoL, once employed by Roman rhetoricians, is now the preferred technique of the world’s memory champions. Although generally used to remember objects, numbers or names, the memory palace may potentially be used to store bits and pieces of autobiographical memories.

Given MoL’s powers in boosting detailed recall, researchers wondered if it could also help the depressed regain access to positive personal memories. They recruited 42 participants with depression – 21 of whom were already in remission – and worked with them to generate 15 elaborate, happy memories to fall back on in times of distress. Next, participants picked a set of loci – either along a familiar route or within a familiar place – and formed appropriate associations between the loci and the above happy memories.

Take participant SH for example. SH deeply cherished an important conversation with her best friend over a cup of coffee one day in New York. To link this memory to her childhood home (one of her selected loci), she visualized the fascia of the house transformed into an outlet of a popular coffee chain. Her friend stood outside, dressed as a barista and beaming brightly at her.

As a control group, some participants were asked to chop 15 of their happy memories into manageable pieces and repeatedly rehearse them – a strategy often used for test preparation. Unlike the MoL, this strategy only boosts recall temporarily.

For three days in the following week, the participants took 8-10min to mentally re-walk to their chosen loci, bringing each associated memory fully and richly to mind as they journeyed. The control group practiced their technique with the same frequency. A week later, back in the lab, researchers asked them to write down as many of these memories as they could. With the mnemonics fresh in mind, both groups showed a similar increase their ability to access vivid details of the happy memories, and reported that reflecting on these positive nuggets enhanced their mood. Correspondingly, both groups scored lower on the Beck Depressive Inventory, although the improvement was not significant. These results suggest that in terms of immediate benefits, MoL was not superior to the control memory technique.

Time 2: first recall test after a week of practise. Time 3: surprise recall test a week later

Time 2: first recall test after a week of practise. Time 3: surprise recall test a week later

A week later, researchers surprised the participants with a follow-up recall test. This time, a dramatic difference emerged (graph above): the control group lost their memory edge, on average forgetting 2 of their repeatedly rehearsed memories. Those trained with MoL, on the other hand, easily retrieved almost every single one of their happy moments. Unfortunately, as this last test was conducted through a telephone call, the researchers did not measure changes in the participants' depressive symptoms.

Nevertheless, this encouraging result suggests that MoL is effective at helping those with depression access their "happy place", even a week after initial training. However, it's important to keep in mind that while the participants reported feeling better, they did not score significantly better on the depression scale. Since both researchers and participants knew the goal of the experiment, a self-reported improvement in mood could just be placebo effect.

Next, researchers will have to figure out if increased access to happy memories actually repairs mood in people with depression and whether (and how) MoL can be used in day-to-day life to guard against dramatic downturns in mood. If so, how much training is required to establish a stable memory palace in the first place, so that it can be easily accessed months or years after initial learning? Will they need intermittent booster sessions? Could MoL improve symptoms of depression of than mood?

Tim Dalgleish, Lauren Navrady, Elinor Bird, Emma Hill, Barnaby D. Dunn, & Ann-Marie Golden (2013). Method-of-Loci as a Mnemonic Device to Facilitate Access to Self-Affirming Personal Memories for Individuals With Depression Clinical Psychological Science, 156-162 DOI: 10.1177/2167702612468111