A Look at Some Memorable Brains

Abstract & Commentary

Source: Maguire EA, et al. Routes to remembering: The brains behind superior memory. Nat Neurosci. 2003;6(1): 90-95.

Disorders of memory are frequently studied, but exceptional recall abilities have been the subject of relatively few investigations. In an effort to understand the neural basis of superior recall, Maguire and associates examined 8 participants in the World Memory Championships, a competition held annually in London. These individuals averaged nearly 34 years of age and had practiced the use of memory-enhancing strategies (mnemonics) for an average of 11 years. Most used an ancient mnemonic strategy known as the "Method of Loci," in which the items to be recalled are associated with a well-learned route or other mentally visualized locations. Maguire et al used neuropsychological testing, quantitative analysis of MRIs by voxel-based morphometry, and functional MRI (fMRI) to compare the superior memorizers (SM) to age-matched normal controls.

The performance of the SM and controls on the neuropsychological test was similar in terms of verbal IQ, reasoning ability, and visual recall. However, there were differences observed in the ability to repeat random sequences of digits (digit span). The SM were able to repeat an average of 16.8 digits presented orally, while controls scored only 12 digits forward. In addition, performance on measures of verbal memory, such as the Story Recall Test and the Subjective Memory Questionnaire, also favored the SM over those with normal memory abilities.

The gross structure of the brains of the SM did not differ significantly from that of controls. The fMRI studies, however, did reveal differences. The tasks used in the fMRI studied included recall of digits, faces, and the patterns in drawings of snowflakes. The SM were better at memorizing things that could be more readily described verbally, such as digits and faces, but they were not better than controls at recalling stimuli that could not readily be verbally encoded, such as the random patterns of snowflakes. Across fMRI tasks, the SM more extensively activated the right hippocampus, the medial parietal cortex, and the retrosplenial cortex than did their age-matched counterparts. These regions of the brain are known to be important for certain aspects of memory, especially spatial memory and navigation. Maguire et al suggest that the greater activation of these areas in the brains of the SM relates to their use of the Method of Loci to improve their recall performance. They conclude that fMRI may be useful in future studies of the neural basis of mnemonic strategies.

Commentary

It would be of great value to understand how some individuals develop exceptional recall abilities. That knowledge might lead to improved strategies for education, methods to preserve recall in the elderly, or techniques to remediate memory loss in patients with certain neurologic disorders. This investigation of SM provides some interesting insights into exceptional memory performance and suggests the value of applying mnemonics for memorization enhancement.

It is notable that the SM in this study were not better at recalling visual patterns than the age-matched controls. They apparently did not have eidetic recall (photographic memory), the ability to remember scenes in comparable detail to examining a photograph. There is no evidence that true eidetic recall can be learned or acquired through the use of any known mnemonic strategies. Verbal recall abilities, however, can be enhanced through techniques such as the Method of Loci, which has been used successfully for this purpose for more than 2000 years. This fMRI study provides evidence that brain areas specialized for spatial recall are recruited when the Method of Loci is used. In terms of clinical benefit from the use of this mnemonic strategy, it seems likely that this strategy would succeed only in patients in whom these brain regions remain intact. Considerable effort is required to successfully learn and apply this mnemonic technique in a real-world setting, and it is, therefore, useful to know which patients it would or would not benefit.

As Maguire et al suggest, fMRI may be a valuable tool with which to examine the neural underpinnings of mnemonics. In addition, fMRI could prove useful in matching particular individuals with the mnemonic strategies that are best suited for them to learn. — Norman R. Relkin

Dr. Relkin is Associate Professor of Clinical Neurology ad Neuroscience, New York Presbyterian Hospital-Cornell Campus.