By Jalwa Alfroz

As humans age, it is normal for cognitive skills, such as memory, to decline. However, some people seem to escape this fate, and are subsequently categorized as super-agers. Investigators at the Harvard-affiliated Massachusetts General Hospital, led by Dr. Bradford Dickerson, revealed that certain areas of the brains of older adults with extraordinary memory performance looked similar to those of young adults. Previously, super-aging studies had only compared the brains of people over 85 years old to those in their middle ages.

The current study focused on people around the typical retirement age, mostly in their sixties and seventies, and compared their memories to those of twenty year olds. Forty adults aged 60-80 years old were enrolled. From these participants, 17 adults performed better on memory tests than 41 young adults aged 18-32 years old. The study used a hypothesis-driven approach and focused on two large-scale intrinsic brain networks known to be important in memory. One of the networks was the default mode network, which is shown to play a role in learning and remembering new information. The network includes the salience network, which helps translate certain information as important or urgent. Whole-brain resting-state fMRI data was processed and the posterior cingulate cortex was used to identify the default mode network, while the right dorsal anterior insula was used to identify the salience network. Correlation maps of the two networks in all study participants were converted to z values, using Fischer’s r-to-z transformation and were averaged across all subjects.

Researchers not only showed that there was no shrinkage in the default mode network, the volume of the hippocampus, and the salience network in super-agers compared to those of typical older adults, but also that the size of these regions correlated with memory ability. In fact, the preserved cortical thickness and hippocampal volume in super-agers was statistically indistinguishable from young adults. This correlation between brain size and memory was found in the para-midcingulate cortex, an area in the brain that intersects the salience and default mode networks. Effective communication between these networks is crucial for healthy cognitive aging. Therefore, understanding the networks in the brain that protects against memory decline could potentially lead to advances in treatment of dementia and other age-related disorders.

References:

1. W. Sun, et al., Youthful brains in older adults: preserved neuroanatomy in the default mode and salience networks contributes to youthful memory in superaging. The Journal of Neuroscience 36, 9659-9668 (2016). doi: 10.1523/jnuerosci.1492-16.2016.
2. Image retrieved from: http://www.huffingtonpost.com/2013/08/23/super-agers_n_3804213.html