SuperAgers have neurons in the brain region called the entorhinal cortex that are larger than in peers 20-30 years younger. SuperAgers is a term for individuals whose brains age slower than average and have brain functions at least as good as individuals decades younger.
It also appears that these large neuron cells were present from birth and are maintained structurally throughout their lives. The study was done by researchers at Northwestern University Feinberg School of Medicine.
The study of SuperAgers 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 Entorhinal Cortex Controls Memory
Scientists studied the entorhinal cortex of the brain because it controls memory and is one of the first locations targeted by Alzheimer’s disease. 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 SuperAgers 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.
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. 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 reasons that remain unknown, cell populations in the entorhinal cortex are selectively vulnerable to tau tangle formation during normal aging and in early stages of Alzheimer’s. In the study, Alzheimer’s, neuronal shrinkage (atrophy) in the entorhinal cortex appears to be a characteristic marker of the disease.
Future studies are needed to understand how and why neuronal integrity is preserved in SuperAgers. The researchers plan to look at the chemical, metabolic or genetic features of these cells that render them resilient.
Source: Integrity of neuronal size in the entorhinal cortex is a biologic substrate of exceptional cognitive aging
This article is based on the press release from Northwestern University. Content may be edited.