Author: Brander Sattler
From: East Meadow, NY, USA
Think about everything you touch and the texture of that object. Think about everything you see and how it makes you feel. Think about everything you hear and your reaction to that sound. Now ask yourself: how does this all happen? The answer: neurons (also known as nerve cells). Neurons are the basic building block of our brain and nervous system. They take in sensory information from the outside world, transfer up to the brain for integration, and transfer the signal from the brain to the rest of the body so you can react to that sensory information. However, when we age, neurons often shrink and retract their dendrites (used for sending neural impulses to other neurons) and the myelin tissue (wraps around the axon, which is used to send signals). This shrinking and retracting decreases the synapses (connections), between brain cells, which worsens learning and memory. But what if I told you there was a way our body can repair these damaged neurons. It is called neurogenesis - the regeneration of neurons. Recent studies have shown that neurogenesis can occur in individuals of all ages, including the elderly. Let’s discover what evidence there is for this and what this means in the larger context!!
Evidence of Neurogenesis in Older Individuals
For the longest time, neuroscientists have believed that neurogenesis only occurs during development. However, recent studies have shown that neurogenesis not only continues into adulthood, but into late adulthood. Early attempts to show evidence for neurogenesis in adults included Altman in the 1960s and Kaplan & Hinds in the 1970s. However, these earlier studies did not provide evidence that was convincing enough to persuade the neuroscience community and the general public that neurogenesis occurs past adolescence. In the 1980s, Nottebohm provided more convincing evidence of neurogenesis in adults when he performed a study that showed neurogenesis in adult birds and compared their nerve cells to our nerve cells. Labs in the 1990s built off of Nottebohm’s study, showing that there is neurogenesis in the adult hippocampus (used for memory), more specifically the SGZ (subgranular zone). Although recent studies have shown that neurogenesis gradually decreases with age, neurogenesis is still present in older adults. Since the hippocampus deals with memory, what effect does neurogenesis in this region have on the elderly? Since AD greatly affects a patient’s memory, what effect does this neurogenesis have on AD treatment and therapy?
Possible AD Therapy?
Recent studies have shown that Alzheimer’s Disease is closely related to neurogenesis and the number of neurons a person has. For example, in a study published in 2019, Llorens-Martin and her colleagues confirmed that the number of neurons in patients with Alzheimer’s disease was a lot fewer than the number of neurons in patients without Alzheimer’s disease. In addition, Orly Lazarov (from the University of Chicago) concluded two major findings: more neurogenesis correlates with better cognitive abilities in older adults, and that neurogenesis is impaired early in Alzheimer’s disease. These two findings show that increasing the amount of neurogenesis in older adults can possibly reduce the chances of acquiring AD because a reduction in neurogenesis correlates with AD. However, humans are the only species that acquire AD. As a result, there are no animal models to test an increase in neurogenesis, so this possible medication that can provide AD therapy remains controversial. What does the future of this possible AD therapy entail?
Conclusion
Although recent evidence has shown a decline in neurogenesis in people diagnosed with AD, the extent to which this decline in neurogenesis affects the cognitive decline seen in AD patients remains poorly understood. In addition, the lack of animal testing available to test a possible AD therapy remains a hurdle that has to be overcome. Studying neurogenesis is a step in the right direction towards a possible AD therapy, but we still have a long way to go.
Author: Branden Sattler
Branden is a rising junior at East Meadow High School. He has a passion for psychology and wants to understand how different aspects of life affect a person’s emotional well-being.
References
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Yeager, A. (2019, March 25). More Evidence that Humans Do Appear to Create New Neurons in Old Age. The Scientist Magazine®. https://www.the-scientist.com/news-opinion/more-evidence-that-humans-do-appear-to-create-new-neurons-in-old-age-65650#:%7E:text=The%20results%20show%20that%20neurogenesis,disease%2C%20regardless%20of%20their%20age.
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