Superagers With Sharp Memories in Their 80s Have Larger Nerve Cells

Highlights:

As people age, their brain tends to shrink in size and their memory gets worse
But some elderly individuals above 80 years of age retain sharp memory skills
This occurs due to a brain region involved in attention, which offers a clue to Alzheimer’s disease

Nerve cells present in an area of the brain responsible for memory were significantly larger in Super Agers compared to cognitively average peers, reports a new Northwestern Medicine study.

The remarkable observation that Super Agers showed larger neurons than their younger peers may imply that large cells were present from birth and are maintained structurally throughout their lives ().

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Ageing is referred to the accumulation of changes that brings a person closer to death.

‘Super Agers may have a particularly keen sense of attention that helps to support their memory, which is useful in treating Alzheimer’s disease.’

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The study of Super Agers with exceptional memory was the first to show that these individuals carry a unique biological signature that comprises larger and healthier neurons in the entorhinal cortex that are relatively void of tau tangles (pathology). The findings will be published in the Journal of Neuroscience.

Larger Neurons: Biological Signature of Super Aging Trajectory

To understand how and why people may be resistant to developing Alzheimer’s disease, it is important to closely investigate the post-mortem brains of Super Agers.

Scientists studied the entorhinal cortex of the brain because it controls memory and is one of the first locations targeted by Alzheimer’s disease.

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The entorhinal cortex comprises six layers of neurons packed on top of one another. Layer II, in particular, receives information from other memory centers and is a very specific and crucial hub along the brain’s memory circuit.

In the study, scientists show that Super Agers harbor large, healthier neurons in layer II of the entorhinal cortex compared to their same-aged peers, individuals with early stages of Alzheimer’s disease, and even individuals 20 to 30 years younger. They also showed that these large layer II neurons were spared from the formation of tau tangles.

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Taken together, the findings suggest that a neuron spared from tangle formation can maintain its structural integrity (i.e., remain healthy and large). The inverse also seems to be true: Tau tangles can lead to neuronal shrinkage.

For the study, scientists examined the brains of six SuperAgers, seven cognitively average elderly individuals, six young individuals, and five individuals with early stages of Alzheimer’s ().

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Then they measured the size of neurons in layer II of the entorhinal cortex (compared to layers III and V). They also measured the presence of tau tangles in these cases.

For that remain unknown, cell populations in the entorhinal cortex are selectively vulnerable to tau tangle formation during normal aging and in the early stages of Alzheimer’s.

Researchers suspect this process is a function of tau tangle formation in the affected cells leading to poor memory abilities in older age. Identifying this contributing factor (and every contributing factor) is crucial to the early identification of Alzheimer’s, monitoring its course, and guiding treatment.

Future studies are needed to understand how and why neuronal integrity is preserved in SuperAgers. Researchers want to focus on probing the cellular environment.

References:

Ageing and the brain - (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2596698/)
What Happens to the Brain in Alzheimer's Disease? - (https://www.nia.nih.gov/health/what-happens-brain-alzheimers-disease)

Source-Medindia