Pump Up Your Brain

Biology concepts – learning, memory, attention, concentration, hippocampus, neurotransmitters, neurotrophins, executive function, processing speed, exercise

Many people exercise because of how it makes them feel, or just because they think it helps them think more clearly - maybe by reducing stress. They will be happy to know that exercise actually increases the power of your brain, everything from learning, to memory, to attention, to decision making speed.

Many years ago, my father told me the story of how he studied while in college. He would hit the books in a solitary, silent room and just cram until he couldn’t concentrate anymore. Then he would get up, go outside, and run laps around his dorm for a while. Then he would come back and start again. Study, run, repeat. Turns out, the running makes a true difference. Exercise can actually make you smarter!

In a study from 2011, researchers took overweight kids and had them start exercising. Those that had at least 30 minutes of physical activity each day showed increased hippocampus size, and significant improvement on a CAS planning test, an alternative to the standard IQ test.

Planning basically means that their executive function (planning, reasoning, and decision making skills) had improved markedly. They also performed much higher on a math test, even though no additional math instruction had been given.

Exercise has impacts on memory, learning, attention, concentration, and processing speed. So now we know what we are talking about when we say exercise helps learning. Oh – you won’t just take my word that exercising helps? Good, always ask for evidence.

Let’s look at studies just from 2013, although there are many older studies. One study found that a single bout of moderate exercise allowed participants to more accurately complete a test on memory, reason, and planning - and it took them less time. Another study indicated that exercise reduced the loss of cognitive function in middle-aged women. Yet another publication talked about how master athletes (over 50), have a larger brain volume and better cognitive function as compared to their sedentary counterparts.

We can go on. Exercise has been shown to support the cellular structure of the white matter (myelinated) neurons of the cerebral cortex in patients with vascular disease, important for higher thinking functions. And another study shows that processing speed is increased after starting a regular regimen of cardiovascular activity.

The upper image shows where the hippocampus is located within the brain. There are two, one in each hemisphere. They are connected as well. The lower image shows the regions of the hippocampus, including the dentate gyrus (DG) the area where much of the neurogenesis after exercise is found.

Finally, we will mention just one of the many 2010 studies. Nine-ten year old kids that exercised regularly had 12% larger hippocampi (plural of hippocampus, part of brain for learning and memory). They were faster on recall tests and they learned new information faster.

So now that you are convinced that exercise does help cognitive functions, the question still remains as to how exercise carries out this miracle. The first thing to get clear is the difference between memory and learning. It might seem that they are the same thing; you have some experience, either verbal, aural, visual, etc. and if you remember it, then you have learned it. But there are subtle differences.

Specialists define learning as a process that will modify a subsequent behavior. Memory, on the other hand, is the ability to remember past experiences. Memory is the record left by a learning process, so you need to have memory to learn. You learn to play piano by studying the notes and the instrument, but you then play it by using your memory to retrieve the notes and fingering that you have learned.

Back to the mechanisms of how exercise help memory and learning. The easy explanation is that exercise helps you sleep, improves your mood, and drives more oxygen to the brain. These undoubtedly help you study better or even notice more that can be used to build knowledge. These are the factors my dad counted on when he went running. But there’s much more.

The hippocampus is important for learning and memory. Many studies of exercise and cognitive function have shown increases in the size of this part of the brain in exercise participants. Those kids that increased their “IQ,” they had an increased hippocampus. So did mice from studies in the 1990’s.

A lot of the benefits from cardiovascular exercise come through the making of new neurons (neurogenesis). Yep, this is a huge exception to the rule that central nervous system neurons last your entire life and can’t be recovered or new ones produced. Neurogenesis is how the hippocampi of all those exercisers got bigger.

Regular exercise induces neurogenesis through action of brain chemicals, trophins and NTs. We talked about brain-derived neurotrophic factor (BDNF) 2 weeks ago with respect to mood and we said we revisit this factor. This neurotrophin actually stimulates your brain to make new neurons! More neurons means more connections, and more potential learning.

Think of plasticity as a general process, the altering of neurons and their connections. It involves making more neurons (neurogenesis) and the number (developmental plasticityor synaptogenesis) and orientation of the dendritic connections with other neurons (synaptic plasticity).

The images show the increase in the number of dendrites and possible synaptic junctions over time. The increase in dendrites is called arborization (arbor = tree) for obvious reasons. The increase in synapses is called synaptogenesis. Exercise increases both of these. This image isn’t a result of exercise, but it would be is similar.

BDNF doesn’t just induce new neuron formation, it can increase the number and size of the connections (synapses) between neurons. IGF-1 is probably involved in this as well, as its main function is to support the growth of fragile, newly formed neurons and connections.

Plasticity is crucial to learning and to memory, since all learning and memory is just a map of connected circuits that work together to access certain information. It is the number and pattern of the connections that determine the amount retained. More connections must help this process.

LTP is for memory and learning – the reinforcing of neural connections to make them stronger. Exercise increases LTP, probably through synaptic plasticity, more connections between two neurons would help reinforce each other when they fire. We talked about LTP last year, so read that post and know that exercise increases it.

Unfortunately, for best increases in memory the exercise must be long term. In a 2013 study, neurogenesis was apparent only 14 days after initiation of exercise, and these were immature neurons. LTP wasn’t increased appreciably until 56 days.

Increased speed probably comes through increased IGF-1 and oxygenation, and their effects on the support cells in the brain. Oligodendrocytes and astrocytes help the neurons do their job at peak efficiency. In particular, oligodendrocytes make the myelin sheath that increases transmission speed.

Meet the glial cells. Astrocytes mediate the travel of fluids and nutrients from the capillaries to the neurons and between the neurons and the cerebrospinal fluid. Oligodendrocytes make the myelin sheath around some axons. Microglial cells are the immune system of the brain, they phagocytose intruders. Finally, the ependymal cells line the ventricles in the brain, the spaces that hold the cerebrospinal fluid.

Astrocytes, on the other hand, are important for blood flow to neurons, and cerebral spinal fluid movement. These two functions would be particularly important for moving neurotrophic factors toward the neurons.

Exercise also helps your attention and concentration. And no, these two aren’t exactly the same. They’re more closely related than memory is to learning, but there are still some differences. Both are important for making you smarter, because only by focusing do we take information in – you have to notice something to learn it.

When you are in a room full of people talking, you can still follow the conversation between yourself and one other person. This is one of several different forms of attention. In general, attention is a thinking process for directing and maintaining awareness of stimuli in one’s environment.

Concentration is the ability to control attention for a sustained period. Attention shifts as we wander from thought to thought about different things in our mind or environment, but concentration requires attention to one thing without wandering. In more clinical terms, concentration is a combination of two types of attention; sustained attention and selective attention.

Sustained attentionis staying on task, keeping your mind on a single task over time. Selective attention is more about how you pick what you pay attention to. If there are many activities going on within range of your sense, but you focus on one thing and pay no attention to the others, that is selective attention.

Attention span is not equal to sustained attention. It is focused attention; how long until your brain diverts to some other stimulus. In 2000, Americans had a 12 second attention span on average. In 2010, it was down to 8 seconds. Heck, a goldfish has a 9 second attention span, and we make fun of them!

Attention is centered in the reticular activating system (RAS), near the brain stem. But it connects to other centers that work in attention as well, like the prefrontal cortex and the parietal cortex. The RAS accounts for shifts in levels of awareness to different things. Exercise activates the RAS, which increases alertness, and therefore attention and concentration – my dad was ahead of his time.

It turns out that increased dopamine, serotonin, and norepinephrine in the brain, and particularly the RAS is crucial for attention and concentration. And we talked two weeks ago about how exercise increases all these. In ADHD, they give drugs (methylphenidate) that increase the apparent levels of dopamine. This helps us make sense of studies that show regular exercise alleviates the symptoms of ADD/ADHD.

One last point that I find interesting. The type of exercise seems to make a difference for the increase in neurotrophins. A 2012 studyshowed that rats that ran on exercise wheels had increased BDNF in the hippocampus, but rats that lifted weights (climbed ladders with weights on their tails) increased only IGF-1. The two proteins work in different pathways, so rat studies show us that it is best to include both aerobic and resistance training in your exercise program. And a rat shall lead them.

Next week, can you die from not getting enough sleep. Yep, and that's not the weirdest part of fatal familial insomnia.

For a good resource on brain structure and function, see the Open College’s interactive brain.