‘Superagers’ with sharp memories in their 80s have larger neurons

Neurons in a part of the brain involved in memory may be 10 per cent larger in superagers than others aged 80 or over

By Carissa Wong

“Superagers” – people aged 80 or over with exceptionally good memories – may have larger than expected neurons in a region of the brain that is critical for memory.

With age, most people experience a gradual decline to their memory, but some maintain a remarkable ability to recall past events into their eighties or older, on par with people 20 to 30 years younger.

Alongside a decline in memory, our brains naturally shrink with age, with previous studies suggesting this occurs less with superagers.

Now, researchers have shown that superagers may have larger than expected neurons in their entorhinal cortex, a component of the brain’s memory system.

Tamar Gefen at Northwestern University in Illinois and her colleagues imaged brains donated by six superagers who died at an average age of 91. The six individuals previously took part in ongoing research into superagers.

These images were compared with seven people who died at an average age of 89 and a further six people who died at an average of 49, all of whom had memories that would be considered normal for their age.

Among the superagers, their entorhinal cortex neurons were around 10 per cent larger than those of the people who died at a similar age with a to-be-expected memory.

The superagers’ neurons were even around 5 per cent larger than the people who died 40 years younger, suggesting that larger than average neurons may contribute to an exceptional memory at age 80 or over.

The superagers also had substantially fewer protein clumps called tau tangles inside their neurons than their counterparts who died at a similar age. An abnormal build-up of tau has been suggested as a cause of Alzheimer’s disease.

“I am not yet sure why larger neurons are associated with preserved memory other than that they are more resistant to tau tangles,” says Gefen. “One other hypothesis is that they are more structurally sound and can generate more optimal [neural connections].”

“[The overall study] adds to the growing evidence that superagers differ from typical adults on multiple levels of the brain,” says Alexandra Touroutoglou at Harvard Medical School.

“The sample size here is relatively small, but that’s understandable. Superagers are a rare group, so finding a good number of them in a postmortem brain study is difficult,“ she says.

According to Joseph Andreano, also at Harvard Medical School, other brain regions linked to cognition have been shown to differ in size in superagers compared with people with a to-be-expected memory. It is unclear whether neuron size in the entorhinal cortex specifically accounts for enhanced memory, he says.