They say you can’t teach an old dog new tricks – but maybe you can have an old brain grow new neurons. New research published in Nature Medicine has shed some light onto the debated topic of whether adult brains can create new neurons in the hippocampus, the region of the brain that is important in short- and long-term memory consolidation. As you might expect, it is one of the most affected areas in Alzheimer’s disease, begging the question of how strengthening the connections in this region in older people may impact Alzheimer’s.

However, it isn’t even known whether neurogenesis, the process of making new neurons, continues in the hippocampus past childhood. Studying the brain is hard (as you might suspect) – the lack of well-preserved human brain tissue and various techniques to study and identify newly-formed neurons has created conflicting data and debate around neurogenesis in the hippocampus.

This study offers fuel into the Alzheimer’s fire. By utilizing highly controlled tissue collection methods and state-of-the-art tissue processing techniques, the researchers found thousands of newly formed neurons in 13 healthy brains from age 43 up to age 87 with a slight age-related decline in neurogenesis (about 30% from youngest to oldest). (The image above shows new neurons in red in brain tissue from a 68-year-old.) In stark contrast, 45 Alzheimer’s brains from people age 52 to 97 had lower amounts of new neurons (an average of 30% fewer neurons compared to age-matched healthy brains). Those with more severe Alzheimer’s showed less new neuron formation than those with milder disease, indicating a sharp and progressive decline in neurogenesis. The fact that Alzheimer’s patients showed less newly-formed neurons over a wide age range suggests that the disease isn’t simply a function of aging, but has other measurable pathological changes.

Maybe sparking neuron creation in the hippocampus can provide an alternate route to new therapies? This comes as a beacon of hope after the recent rattling news of yet another major Alzheimer’s drug failure in Phase III clinical trials. So far, some work in mouse models of Alzheimer’s has shown that certain drugs and exercise can decrease their cognitive deficits. More research is definitely needed to replicate and verify these findings, as well as translate these findings to humans.

 

Managing Correspondent: Chelsea Weidman Burke

Press Articles: Debate about birth of new neurons in adult brains extends to Alzheimer’s disease, Nature

New neurons for life? Old people can still make fresh brain cells, study finds, Science

More Evidence that Humans Do Appear to Create New Neurons in Old Age, The Scientist

Our brains may be able to make new neurons throughout adulthood, New Scientist

Old brains still make neurons, study finds, offering a possible way to protect against Alzheimer’s, STAT

Original Journal Article: Adult hippocampal neurogenesis is abundant in neurologically healthy subjects and drops sharply in patients with Alzheimer’s disease, Nature Medicine

Image Credit: Llorens-Martín lab, Nature Medicine paper

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