Very old people have more neurons than young 20-30 year olds
People over 80 who have as good a memory as younger people are called ‘very old people’. A new study found that very old people have significantly larger neurons in the regions of the brain responsible for memory than their average cognitive peers, people with early-stage Alzheimer’s disease, and even those 20 to 30 years younger.
These neurons also lacked the tau (a protein responsible for maintaining the stability of microtubules, the transport pathways for neurotransmitters) that is characteristic of Alzheimer’s disease.
Lead author Tamar Geffen, professor of psychiatry and behavioral science at Northwestern University School of Medicine in the US, said, “The fact that very old people have larger neurons than younger people may suggest that large cells are present at birth and have remained structurally throughout their lives. “The conclusion is that larger neurons are a biological feature of the super-senile pathway.”
Northwestern University’s Advanced Aging Research Program studies a unique group of people known as the very old. This study shows for the first time that very old people have a unique biological characteristic that includes larger and healthier neurons in the endocardial cortex, and are relatively free of tau tangles.
“It is important to scrutinize the brains of very old people after death to understand how and why they resist Alzheimer’s,” says Geffen. Based on this, research is being carried out on ‘what makes the brains of very old people unique’ and ‘how we can use their biological properties to help prevent Alzheimer’s disease in the elderly’.
The research team focused on the entorhinal cortex of the brain. This is because the brain’s entorhinal cortex controls memory and is a target for Alzheimer’s disease. The entorhinal cortex consists of six layers of neurons superimposed on each other. Specifically, the second layer, which receives information from other memory centers, is a specific and very important hub in the brain’s memory circuits.
The study shows that older people have larger and healthier neurons in the second layer of the entorhinal cortex than people their age, those with early stages of Alzheimer’s disease, and those 20 to 30 years younger. And it shows that the large neurons in the second layer are released from the tau tangent. Tau tangles can lead to nerve contractions.
Participants in the advanced geriatric study donate brains after death. For this study, the brains of 6 elderly people, 7 cognitively average elderly people, 6 young people, and 5 early stage Alzheimer’s people were examined. The team measured the size of the neurons in the second layer of the endothelial cortex and looked for tau tangles.
Cell populations in the inner cortex tend to get stuck during normal aging and the early stages of Alzheimer’s. “This study shows that nerve shrinkage (atrophy) in the endothelial cortex is a hallmark of Alzheimer’s disease,” said Geffen.
Further research is needed to understand how and why neuronal integrity is preserved in older people.
The study was published in the journal Neuroscience. The original title is ‘Neuronal Integrity in SuperAging’.