Particular parts of the brain shrink with age, mostly the prefrontal cortex (a zone at the front of the frontal lobe) and the hippocampus (a part of the limbic system located above the brain stem and below the cortex). Both areas are associated with learning, memory, planning, and other complex mental activities.

Shrinkage of these brain areas kick-starts a decline in a person's ability to learn new things, retrieve information, and ability to perform tasks of attention, learning, and memory.

A study published in The Journal of Neuroscience offers clues as to why some people - dubbed as super agers - retain these abilities of resilient memory and youthful thinking, and preserve the brain areas that are linked to those abilities.

Bradford Dickerson, M.D., director of the Frontotemporal Disorders Unit at Massachusetts General Hospital (MGH) Department of Neurology, and Lisa Feldman Barrett, Ph.D., M.G.H. Department of Psychiatry - who are co-senior authors of the new study - aimed to investigate how super aging adults differ from other older adults who display expected traits of memory deterioration.

The MGH team enrolled 40 older adults between 70-80 years and 41 younger adults between 18-35 years. While 23 of the older participants exhibited normal results for their age group, 17 of the older participants performed equally well to younger adults 4-5 decades younger than them.

"Previous research on super aging has compared people over age 85 to those who are middle-aged," says Alexandra Touroutoglou, Ph.D., M.G.H. Neurology, co-senior author with Dickerson and Barrett. "Our study is exciting because we focused on people around or just after typical retirement age - mostly in their 60s and 70s - and investigated those who could remember as well as people in their 20s."

Brain region thickness comparable in super agers and young adults

Touroutoglou and colleagues conducted imaging studies on the brains of the super agers that revealed that the prefrontal cortex and hippocampus (that typically shrink with age) were similar in size to those of young adults.

"We looked at a set of brain areas known as the default mode network, which has been associated with the ability to learn and remember new information, and found that those areas, particularly the hippocampus and medial prefrontal cortex, were thicker in super agers than in other older adults. In some cases, there was no difference in thickness between super agers and young adults," Touroutoglou says.

Barrett points out that the team also examined a group of regions in the brain known as the salience network - involved in identifying information that is important and that needs attention for specific situations - and found that several areas had preserved thickness among super-agers, including the anterior insula and orbitofrontal cortex.

No shrinkage was observed in these brain networks and, furthermore, the size of these regions correlated with memory ability. The area in which the correlation was most noticeable was at the intersection of the salience and default mode networks. Previous studies have shown this region to be significant in allowing different brain networks to communicate efficiently.

"We believe that effective communication between these networks is very important for healthy cognitive aging," says Touroutoglou, an instructor in Neurology at Harvard Medical School.  
 "We desperately need to understand how some older adults are able to function very well into their seventh, eighth, and ninth decades. This could provide important clues about how to prevent the decline in memory and thinking that accompanies aging in most of us."

Bradford Dickerson, M.
Dickerson concludes by saying that recognizing the factors that protect against memory decline could lead to advances in preventing and treating age-related memory loss and potentially even dementia.