supermembrain

By Manying Lo (Bugle Team)

I remember the time my first tooth fell out. It was loosely hanging from my gums so my brother decided that it might be a good idea to tie a string around it and, well, I’ll let you guess the rest. Although this memory remains vividly in my mind, there are many events that I cannot remember clearly. Yet, if you are an individual with Highly Superior Autobiographical Memory (HSAM), then you’d be able to recall your past with incredible accuracy.

Highly Superior Autobiographical Memory (HSAM) describes the ability of individuals who are able to accurately recall events from their past, this includes reproducing the dates and day of the week in which the event occurred. A.J. was the first individual to be studied with this kind of ability (Parker, Cahill & McGaugh, 2006). She describes her experience as such: each time she hears a date, she’s able to see a portion of what occurred in her life during that day. She discovered this ability at the age of 11 and has since been able to recall events within her lifetime once she’s been given a date.

To try to find more individuals who may have this ability, Leport et al. (2012) conducted a study where individuals who claimed they had HSAM were screened using several tests. Those who were found to actually have HSAM were then studied to find how they differed behaviourally and in their neuroanatomy from the normal population. They found that individuals with HSAM appear to effortlessly recall dates and memories, distinguishing it from other superior memory abilities that use strategies (such as mnemonics) to encode and retrieve information. Unlike ‘calendar calculators’ who can specify the exact day of the week for dates all across history and are also extremely interested in memorizing dates, HSAM individuals have no particular interest in calendars and dates and can only recall dates in their lifetime. Interestingly, Leport et al. (2012) found that HSAM individuals tend to demonstrate a degree of obsessive-like behaviour. For example, they tend to report organising their memories chronologically or into categories and habitually recalling these memories. Some reported that before sleeping or when they were stuck in traffic, they would recall past events. Another wrote down their memories as if to ‘process the memories better’, whilst others stated that they recalled memories to pass time, sleep or to stay on top of upcoming events. However it’s unknown what relationship this may have with their HSAM and whether some of the individuals would be diagnosed with OCD.

Despite the large amounts of information HSAM individuals can recall, it appears that their abilities are restricted to autobiographical information only. Their performance do not differ from the average population in digit-span forward (recalling increasingly longer sequences of numbers), verbal paired associates (after being read 8 word pairs, recalling the associated word of a chosen word) and visual reproduction tasks (drawing an abstract picture from memory). This is seen in A.J.’s case where she reported that she could not use her memory abilities in school because her encoding was automatic and not strategic (Parker, Cahill & McGaugh, 2006). However, HSAM individuals perform higher in the Logical Memory Test (recalling a story that has just been read to you) and Names-to-Faces task (after being shown pictures and read their names, being able to recall the name associated with the face).  This seems to make sense, it’s possible that individuals are using the same strategies to obtain information in real life and in such tests (Leport et al., 2012).

In terms of their neuroanatomy, HSAM individuals do show differences compared to the normal population. In the same study, Leport et al. (2012) found structural differences in the region of the inferior and middle temporal gyri and temporal pole, the anterior insula and the parahippocampal gyrus. Past research has shown that the right temporal pole and medial temporal gyrus, the parahippocampus and right anterior insula are more engaged when participants listen to sentences about their own past compared to someone else’s past (Fink et al., 1996). On the contrary, individuals with lesions to the left medial temporal region and bilateral middle temporal gyri show retrograde memory loss (loss of memories of the past). Therefore, it appears that such regions are associated with the ability found in HSAM individuals.

Other areas that also appear to contribute the HSAM ability are the inferior parietal sulcus, the inferior parietal lobule and areas of the uncinated fascicle. The uncinated fascicle is responsible for the recall of declarative information from long term memory storage (Kapur et al., 1992) and has also been found to show preferential activation during an autobiographical ecphory task (Steinvorth et al., 2006).

Before you start to feel terrible about how bad your memory is compared to those with HSAM, consider this: A.J.’s superior memory means that she’s able to hold onto many happy memories but at the same time, she also cannot get rid of any bad memories. She says ‘Most have called it a gift but I call it a burden’. She also feels dominated by her constant remembering which she feels no control over (Parker, Cahill & McGaugh, 2006). So even if you can’t remember something from the past, like an embarrassing moment, sometimes it may be best left that way.

 

 

References

Fink, G. R., Markowitsch, H. J., Reinkemeier, M., Bruckbauer, T., Kessler, J., & Heiss, W. D. (1996). Cerebral representation of one’s own past: neural networks involved in autobiographical memory. The Journal of Neuroscience, 16(13), 4275-4282.

Kapur, N., Ellison, D., Smith, M. P., McLellan, D. L., & Burrows, E. H. (1992). Focal retrograde amnesia following bilateral temporal lobe pathology. Brain, 115(1), 73-85.

LePort, A. K., Mattfeld, A. T., Dickinson-Anson, H., Fallon, J. H., Stark, C. E., Kruggel, F., Cahill, L. & McGaugh, J. L. (2012). Behavioral and neuroanatomical investigation of highly superior autobiographical memory (HSAM). Neurobiology of learning and memory, 98(1), 78-92.

Parker, E. S., Cahill, L., & McGaugh, J. L. (2006). A case of unusual autobiographical remembering. Neurocase, 12(1), 35-49.

Steinvorth, S., Corkin, S., & Halgren, E. (2006). Ecphory of autobiographical memories: An fMRI study of recent and remote memory retrieval. NeuroImage, 30, 285–298.

Image Credit: http://www.messagetoeagle.com/brainsupermemor.php#.Vur8QOKLTIU

 

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