[This post expands on a link from my July 3 post.]
It was once thought that the brain does not generate new brain cells and once a neuron was gone, it was gone forever. This is what I, like many, was told as a kid. As it turns out, recent science shows that not only do humans continue to generate new brain cells throughout life, aerobic exercise fosters a higher rate of neurogenesis, or the birth of neurons.
Scientists say that, in addition to brain degeneration from aging being curbed by increased neurogenesis, the degeneration can be reversed. Evidence suggests that risks for neurodegenerative problems like Alzheimer’s and Parkinson’s can be curbed and symptoms alleviated. Additionally, scientists are noticing brain degeneration in illnesses like depression and ADHD and problems like anxiety and stress and say that these ailments can be fought with neurogenesis.
The science is still young and this is not a miracle cure-all. But it’s clear that aerobic exercise grows more brain cells and has an impact on everything from depression to the likelihood one will develop Alzheimer’s. I’ve liked to three articles with excerpts below the flip. Feed your brain and learn about neurogenesis
Lobes of Steel from The New York Times Magazine:
Other recent studies support this theory. At the University of Illinois at Urbana- Champaign, a group of elderly sedentary people were assigned to either an aerobic exercise program or a regimen of stretching. (The aerobic group walked for at least one hour three times a week.) After six months, their brains were scanned using an M.R.I. Those who had been doing aerobic exercise showed significant growth in several areas of the brain. These results raise the hope that the human brain has the capacity not only to produce new cells but also to add new blood vessels and strengthen neural connections, allowing young neurons to integrate themselves into the wider neural network. “The current findings are the first, to our knowledge, to confirm the benefits of exercise training on brain volume in aging humans,” the authors concluded.
And the benefits aren’t limited to adults. Other University of Illinois scientists have studied school-age children and found that those who have a higher level of aerobic fitness processed information more efficiently; they were quicker on a battery of computerized flashcard tests. The researchers also found that higher levels of aerobic fitness corresponded to better standardized test scores among a set of Illinois public school students. The scientists next plan to study how students’ scores change as their fitness improves.
What is it about exercise that prompts the brain to remake itself? Different scientists have pet theories. One popular hypothesis credits insulin-like growth factor 1, a protein that circulates in the blood and is produced in greater amounts in response to exercise. IGF-1 has trouble entering the brain — it stops at what’s called the “blood-brain barrier” — but exercise is thought to help it to do so, possibly sparking neurogenesis.
Memory: Forgetting Is the New Normal from Time:
Meanwhile, researchers from the Karolinska Institute in Stockholm who have been following over 1,500 people for more than 35 years found a significantly lower rate of dementia, including Alzheimer’s, in those who exercised. Another study, this one of 2,000 elderly men living in Hawaii, showed that those who walked two miles or more a day were half as likely to develop dementia as those who walked a quarter-mile or less.
Cerebral blood volume is not the only thing responsible for this brain-boosting. Also at work is the fact that exercise increases what’s known as brain-derived neurotrophic factor (BDNF), a protein that stimulates the birth of new brain cells and then helps them differentiate and connect. BDNF also enhances neural plasticity, the process by which the brain changes in response to learning. In diseases like Alzheimer’s, depression, Parkinson’s and dementia, BDNF levels are low. In people who exercise, BDNF levels rise.
Head Fake: How Prozac sent the science of depression in the wrong direction from this Sunday’s Boston Globe:
In recent years, scientists have developed a novel theory of what falters in the depressed brain. Instead of seeing the disease as the result of a chemical imbalance, these researchers argue that the brain’s cells are shrinking and dying. This theory has gained momentum in the past few months, with the publication of several high profile scientific papers. The effectiveness of Prozac, these scientists say, has little to do with the amount of serotonin in the brain. Rather, the drug works because it helps heal our neurons, allowing them to grow and thrive again….
“The best way to think about depression is as a mild neurodegenerative disorder,” says Ronald Duman, a professor of psychiatry and pharmacology at Yale. “Your brain cells atrophy, just like in other diseases [such as Alzheimer’s and Parkinson’s]. The only difference with depression is that it’s reversible. The brain can recover”….
Once [mental illness occurs], the brain begins to shut itself down, suppressing all but the most essential upkeep. Not only do neurons stop growing, but the brain seems to stop creating new cells. A 2003 study, led by Columbia University neuroscientist Rene Hen, found that when the birth of new brain cells was blocked with low doses of radiation in “depressed” rats, antidepressants stopped working.
A recent study by Italian researchers, published in the journal Science, helps to reveal another mechanism by which antidepressants reverse the damage of depression. The scientists were interested in seeing if fluoxetine, the active ingredient of Prozac, could increase the potential of brain cells in the adult rat. They studied animals with severe cases of “lazy eye,” a condition characterized by poor vision in one eye due to underdevelopment of the visual cortex. The scientists showed that fluoxetine gave brain cells the ability to take on new roles and form new connections, which erased the symptoms of the disorder.
“The drug appears to make brain cells quite young,” says Jose Vettencourt, a lead author. The scientists are currently repeating the experiment with humans, raising the possibility that fluoxetine will soon be used to treat lazy eye and related conditions.
“Even five years ago, this would have seemed like a very strange idea,” Vettencourt says.
Duman’s lab has demonstrated, in a paper published earlier this year, that physical exercise seems to stimulate the same regenerative pathways. Mice given access to running wheels not only showed reduced anxiety and stress, but also increased levels of the same trophic factors activated by antidepressants. When the activity of these trophic factors was blocked, the benefits of exercise disappeared. The mice stayed stressed, even when they were allowed to run on their wheel.
It is jarring to think of depression in terms of atrophied brain cells, rather than an altered emotional state. It is called “depression,” after all. Yet these scientists argue that the name conceals the fundamental nature of the illness, in which the building blocks of the brain – neurons – start to crumble. This leads, over time, to the shrinking of certain brain structures, like the hippocampus, which the brain needs to function normally.