23 November 2011. Given a random date 30 years ago, most people could not recount exactly what they had for breakfast, the clothes they wore, or events in that evening’s news. But some people with an extraordinary ability known as highly superior autobiographical memory (HSAM) can recall such trivial facts with ease. What is going on in their brains? And could the answer to this question help researchers understand memory loss or dementia? New findings, presented at the 41st annual Society for Neuroscience meeting, held at the Walter E. Washington Convention Center in the nation’s capital on 12-16 November 2011, suggest that certain brain areas are structurally different in these rare mnemonic talents.
In 2006, Larry Cahill and colleagues at the University of California, Irvine, published a paper documenting the first known case of HSAM (see Parker et al., 2006). Since that case was publicized, more people came forward claiming this ability. Cahill’s group confirmed that 20 of them—ranging in age from 25 to 60, with a average age of about 43—have HSAM.
To see what sets people with HSAM apart from everyone else, Aurora Leport and colleagues in the Cahill lab conducted a structural magnetic resonance imaging (MRI) study of 11 of those individuals. She found that several brain areas were unique in people with HSAM. Their insula had a different shape, their lentiform nucleus was larger, and their parahippocampal gyrus and uncinate fascicule had a higher fractional anisotropy (FA) than in controls. The last could mean that white matter tracts are more robust and possibly able to communicate more easily. These brain areas are associated with both autobiographical memory (see Svoboda et al., 2006) and obsessive-compulsive disorder (see Radua and Mataix-Cols, 2009). This could explain why a majority of these volunteers, though they aren’t diagnosed with OCD, seem to have obsessive tendencies such as hoarding and germ-avoidance, said Aurora.
These HSAM regions are affected by atrophy or altered metabolism in Alzheimer’s disease. Even so, Leport and colleagues do not yet know whether these individuals are more or less resistant to Alzheimer’s neuropathology, or why these areas are different in their brains. Future studies will take a look at brain function to see how this unique group forms and retrieves autobiographical memories, as well as the genetics behind the condition.
Music memory, too, may have its own special place carved out in the brain. At SfN, a case study presented by Carsten Finke, Charité University Medicine Berlin, Germany, revealed that a 68-year-old former professional cellist with severe amnesia—both episodic and semantic—not only retained musical memory, but also the ability to learn music. The cellist’s dementia was not due to age or Alzheimer’s pathology. Rather, a bout of herpes encephalitis had destroyed his left temporal lobe, left orbitofrontal cortex, and parts of his right medial temporal lobe in 2005, permanently wiping his ability to name German landmarks, recall autobiographical or historical details, recognize most people, or encode new information.
But while the man, called P.M., could not name well-known composers or famous cellists, his semantic musical memory was substantially intact. He could identify rhythms and intervals in a test of amusia (the inability to recognize or reproduce musical tones). He distinguished orchestral pieces he had known from before his illness from others that were new, and even learned to recognize new musical pieces. The results suggest that semantic musical memory is likely separate from other areas of semantic memory in the brain, said Finke.
P.M.’s frail condition precludes functional brain imaging to examine how he processes music, said Finke, but the group will continue behavioral testing that may probe his abilities. For instance, the researchers want to know whether lyrics influence P.M.’s musical memory. They also want to see whether music therapy might help him, perhaps using his musical ability to compensate for other memory loss.
“Preserved musical memory may provide a window for rehabilitation and enhanced quality of life in patients suffering from memory disorders,” said Finke.
It is not immediately clear if these findings could help researchers studying Alzheimer’s. A recent paper reported that some AD patients fare better than those with semantic dementia at recognizing famous tunes, implicating the right temporal lobe in processing music (see Hsieh et al., 2011). Other studies suggest that the ability to play music remains intact for those with Alzheimer’s, but that patients have trouble recognizing familiar versus unfamiliar tunes (see Baird et al., 2009).
Other research suggests that Alzheimer’s patients respond positively to music, and suggest it as a therapeutic option (see Witzke et al., 2008), and anecdotally, caregivers frequently report that familiar music remains a way of reaching their loved one long after speech has been lost to advanced AD.—Gwyneth Dickey Zakaib.