Something I find very interesting is the relationship between brain function and exercise. I don’t mean just the idea that we feel better when we exercise or that our brain works better when our blood is oxygenated. I’m interested in how lifestyle choices can make the brain work better. Things like daily habits that make us more intelligent and creative.
That’s right; our lifestyle has an effect on how smart we are.
Before going, any further let’s pause and review what happens in the brain when we learn something new. I think we all know that our brain consists of neurons — brain cells — with a nucleus in the center and dendrites, stretching like fingers to the dendrites of other neurons. Learning, thinking, remembering — everything we experience — results from one neuron making an electrochemical contact with another.
The more often one neuron stimulates another, the stronger that connections becomes. That is what learning is. Think about learning a physically complex movement, like driving a stick shift automobile.
At first, it seems like an impossible task — 3 pedals, 1 gearshift and a steering wheel, but only two feet and two hands. Give a little gas, let out the clutch slowly and the engine dies. Alternatively, let out the clutch too fast and the car jerks.
With practice, though, you get better and better until you don’t have to give conscious thought to shifting gears.
The more frequently one neuron stimulates another, the stronger that connection becomes. In terms of brain physiology, the more one practices the stronger and more complex the network of neurons controlling that behavior becomes. This is what learning really is — building strong associations between neurons, creating ever-bigger networks of associated neurons.
I learned some very interesting things about my brain when I broke my left foot. After eight weeks in a cast, my calf atrophied, but so had the network of neurons connecting my foot to my brain.
Long after I built back the muscles in my calf, I would occasionally reach for something to my left, and keep right on going because I had no balance on my left foot. That network of neurons in my brain communicating with the nerves and muscles in my foot had atrophied too.
They no longer had strong connections with one another and the complex interaction between sensing balance in my brain and actuating muscles in my foot was lost. My left foot no longer had the ability to balance like my uninjured foot did.
My physical therapist suggested that I go without shoes whenever possible, and I did. Within just a couple of months, I could balance on my left foot for as long as I wanted. The contact with different surfaces — grass, asphalt, gravel — stimulated the sensory neurons on my foot and helped rehabilitate the neural network in my brain.
However, what was actually going on in my brain to allow this to happen? This is where things get interesting.
Most people over thirty probably remember a high school teacher instructing them not to drink alcohol because it destroys neurons, and neurons are not replaceable — you are born with all you will ever have.
It turns out that isn’t true at all. In the 1990’s scientists began identifying classes of proteins in the brain. One was Brain Derived Neurotrophic Factor (BDNF) first found in the hippocampus, the memory center of the brain. This discovery drew lot of scientific attention and it was quickly established that BDNF is essential to the development of neural networks — that is, brain structures supporting learning and memory.
The thing that is so astonishing about BDNF is that it actually works on the infrastructure of the brain — physical brain growth and expansion. Put some brain cells in a petri dish suspended in nutrients and not much happens. Add a few drops of BDNF and the neurons start growing dendrites and reaching for one another.
In his fascinating book Spark examining the relationship between exercise and the brain, John Ratey refers to BDNF as “Miracle-Gro for the brain”.
According to Ratey, BDNF sends ions to nerve endings, increasing the electrochemical bond, creating stronger and more robust neural networks. It activates brain receptors that make more BDNF, serotonin and other neuron-chemicals that aid the synapses and dendrites in communicating with one another. In short, BDNF is the driver of brain plasticity.
It gets even better.
Ratey tells us that throughout the 1990’s and early 2000’s animal studies proved beyond doubt that exercise and volume of BDNF in the brain correlate with one another. Now, consider this — physical movements are usually associated with learning. We learn by interacting with our world, finding puzzling new things we have not seen before and exploring their properties.
Think of how infants constantly focus their attention on one thing after another. Infants are constantly touching, tasting and feeling the world around them. Learning about the world and physical activity are closely related. Even if we are just moving our eyes, we are physically active. A relationship between physical movement and brain activity supporting learning makes sense.
Finally, in 2007 German researchers found that, people learn vocabulary words 20% faster after exercise than before exercise, and that there is a direct correlation between the rate of learning and levels of BDNF.
However, what is it about exercise that has an effect on the brain? What is the mechanism by which muscle movement assists in memory?
It turns out that when we exercise our muscles produce hormones that have effects on how the brain learns and makes memoires.
Ratey tells us that when we exercise muscles produce a hormone called IGF-1. We have known for some time that IFG-1 assists in delivering glucose to muscles in need of energy, but only recently discovered its role in learning. During exercise, BDNF stimulates uptake of IGF-1 in the brain, activing neurons to produce serotonin and glutamate, two neurotransmitters essential for communication between neurons. At the same time, it increases release of BDNF, enhancing neuro plasticity and the formation of long-term memories.
Another hormone produced in the muscles, VEGF, is essential in producing new blood capillaries and has found some success in naturally building detours around clotted arteries. In the brain, VEGF seems to have an effect on the blood-brain barrier, allowing muscle related hormones to more easily enter the brain.
Finally, FGF-2 helps tissue grow and its role in repairing muscles damaged by exercise is well known. Now we know that FGF-2 is also very active in the brain, assisting with the formation of new brain tissue.
Ratey includes many practical examples of how exercise benefits our brains. He quotes one study in which two groups of over 50 year olds took a memory test following either exercise or watching TV. It is no surprise that the exercise group demonstrated much better recall.
The practical takeaway is that no matter what our age cognitive activity should be interspaced with exercise. Not only is exercise good for our bodies, it is good for our minds as well. The earlier we get in the habit of taking care of our brains when we are young the better it will serve us in old age.
All of this is just touching on the fascinating information Ratey presents in Spark. In it, he explores how exercise can affect depression, anxiety, stress, learning and aging. Using different muscles releases different hormones that affect our brain differently. For instance, animal studies indicate that complex motor skills, the kind developed with dance or balance exercises produced more BDNF than aerobic exercise like running or walking.
Take a walk, jog a little, read a book or learn a language. Your brain needs to serve you for a lifetime and you have to care for it every day.