In 2006, Parker, Cahill and McGaugh reported the first known case of Highly Superior Autobiographical (HSAM) in a research participant known as “AJ”. When provided with a date, AJ could specify on which day of the week it fell and what she did that day. Since then, more people with this extraordinary ability have been identified (click here to view a “60 Minutes” episode on them or here for another Psychology Today blog post on this), and researchers have now discovered structural brain differences in people with HSAM compared to people without it (LePort et al., 2012). This is especially interesting given that people with HSAM do not show exceptional memory in other domains besides autobiographical memory. Among the brain differences that the researchers note is “amplified white matter tract coherence” (p. 12), which they suggest may indicate that the transfer of information among connecting regions is enhanced in participants with HSAM and that this may contribute to their superior autobiographical memories.

As LePort and colleagues point out, however, whether the structural brain differences that they discovered are a cause of HSAM or the result of activities that themselves cause HSAM is not yet known.

It might be easy to jump to the conclusion that people with HSAM are simply born with brains that differ from normal brains and that innate structural differences in the brains of people with HSAM are what allow for their exceptional autobiographical memory abilities. For example, maybe they are born with enhanced connectivity among brain regions critical to autobiographical memory.

A more interesting possibility, however, is that the brain differences (as well as the remarkable autobiographical memory ability) result from unique experiences that occur during development.

Experiences themselves cause changes in the brain to take place. For example, it has long been known that the brains of rats exposed to an enriching environment during development differ from those of rats exposed to an impoverished environment—rats in an enriched environment show increased cortical weight and numbers of glial cells and also show benefits to memory ability.

Research on musical training is an excellent example of how experiences can impact the structure of the human brain, as discussed in this New York Times article and this Scientific American blog and reviewed here. Researchers have known for some time that the brains of musicians differ from those of non-musicians, but researchers have questioned whether this is due to innate differences between musicians and non-musicians. However, recent evidence suggests that musical training itself contributes to the brain differences between the musically trained and untrained. One study showed that children given 15 months of musical training exhibited structural changes in their brain relative those that did not. More recently, researchers at Northwestern showed that neural changes that appear to result from musical training in persist into adulthood.

If structural brain differences between the musically-trained and untrained in adulthood can result from childhood training in that domain, then what type of experience or training could potentially underlie the brain differences shown in people with HSAM?

Actress Marilu Henner, who was one of the participants in the research by McGaugh and colleagues (as shown in this "60 Minutes" episode), may provide some clues in her book on her experience with HSAM and on autobiographical memory. In it, she describes a pastime of hers during childhood. “I decided to play a little game with myself, in which I tried to remember every day that had led up to that moment starting with the most recent What did I do a week ago? Two weeks ago? Three weeks ago? I even started to go back to the previous years and the year before that, remembering specific days from first grade and kindergarten. Over time, this exercise became not only my routine to fall asleep, but also a way to mentally challenge and exercise my brain to the point that I could ‘time-travel’ back to: What did we do each day of our vacation? What was I doing when I was exactly the day my younger brother Lorin’s age? My Niece Lizzy’s age?”

It seems plausible that this type of “training” or memory practice during childhood could lead to structural changes in the brain that are detectable in adulthood and correlated with HSAM.

As McGaugh and colleagues suggest in their article, future research on children with HSAM might shed light on this issue. But perhaps an approach similar to that taken with recent research on musical training could be taken as well. Specifically, maybe children could be randomly assigned to either a no-memory-training control condition or to an autobiographical memory training condition in which they receive a daily autobiographical memory training exercise similar to what Marilu Henner describes in her book. Would structural brain differences be shown 15 months later? If so, would they still be shown in adulthood? Would characteristics of HSAM be found? This would be an interesting study indeed.