Biology concepts – learning, habit, long term potentiation, neural plasticity
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50% of Americans will make at least one New Year resolution, but a quarter of them won’t even make it one week before relapsing. However, those who write down a resolution are much more likely to make changes than those who don’t make a specific demand of themselves. |
First things first, I am not a neurologist. I don’t even play one on TV, but we’re going to delve into some neuroanatomy and neurochemistry here. I’ll try to keep it from making your brain hurt.
Before diving into the gooey mess inside our skulls, we need to know that keeping a resolution means creating a new habit, or breaking an old habit and replacing it with a new one. But, what is a habit anyway?
A habit (from old French meaning “to hold” or “customary practice”) is an extreme form of learning, ingrained to such an extent that we do not think consciously about performing the behavior. But we still have the ability to turn the behavior on or off consciously. This is what separates a habit from an addiction. A poor man’s definition – if you have to decide to do it, it’s not a habit, and if you can’t decide not to do it, it’s an addiction.
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William James was trained as a physician, but was the first professor to start offering psychology classes at the college level. His brother was novelist Henry James, who wrote about the social corruption of England versus the brash selfishness of America. His father was a theologian who worried about the moral evil have thinking about oneself, and Sigmund Fred was a family friend. No wonder William went into psychology. |
Habits are important, they keep us safe and alive for the most part. Good habits aren’t easy to make, while bad habits seem so easy. Bad habits are rewarded at more primitive levels of the brain, and the rewards are more tangible and shorter term. Good choices may be their own reward, but in terms of our brains, they aren’t as strong as a big ice cream sundae.
Rewards reinforce our habits and learning in a chemical sense as well. The reward centers of the brain release a neurotransmitter called dopamine, and we will see below that dopaminergic neurons are very important in learning, memory and making habits.
We need to know how our brains make habits if we want to increase our chances of keeping our resolutions. First comes intent and motivation, then comes learning, then comes making the learned behavior an unconscious act. As it turns out, there are brain centers for all of these, and they are all tangled together.
Dopaminergic neurons release and may respond to dopamine. They are involved in reward, learning, and in reinforcing learning to make habits. Dopaminergic neurons are located in many parts of the brain and a new study shows just how important they are in forming habits.
To help uncover the mechanisms of habit making, a mouse model has been developed that can’t form strong habits. A certain receptor was eliminated from dopaminergic neurons, and then the mice were taught new conditioned behaviors, like stepping on a lever to give them food. They could learn that the lever motion provided food, but they stopped after a while. Normal mice will learn the habit, and just keep stepping on the lever to get more and more food.
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NMDA receptors contribute to LTP by allowing calcium into the cell. This stimulates a retrograde signal that causes the presynaptic neuron to release even more glutamate. This stimulates more NMDA action and even more calcium influx. This loop can literally remain turned on for months! |
LTP results in repeated firing of those neurons, from minutes to months in duration. Every time they fire, that individual pathway gets strengthened. This is the key to learning, called neural plasticity. When neural pathways are repeatedly used, they become strengthened and a behavior is learned or remembered. If they are not used, the connections fade away. Dopaminergic neurons are especially important because they can generate LTP through NMDA receptors but can use additional mechanisms as well.
Many parts of the brain are involved in habit formation, like those that link intent with action. Peter Hall at University of Waterloo near Toronto has been looking at intent and brain function, specifically, a portion of the brain called the superior prefrontal cortex (SPFC), located just behind that place on our forehead where you smack yourself when you do something stupid.
Some people have better SPFC function than others, and they find it easier to act on intentions and make behavior match intention. But good habits can increase SPFC function – see the end of the post.
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Adolescent brains are maturing at an astonishing rate during the teen years, but the maturation is uneven. This means that they often revert to the more primitive, emotional brain for decision making. The emotional brain includes the reward center, so teens are more likely to make habits based on short-term rewards. Good school work and behavior habits are tough to develop in these befuddled brains. |
The entire prefrontal cortex is a big player here, as this is the seat of the executive function, those functions of the brain that control and manage other thinking; like planning, problem solving, resisting immediate reward, and mental flexibility. It boils down to this: the PFC is the chief weigher of risk vs. reward and is the boss decision maker – although he often listens to the primitive brain that, “wants what it wants, when it wants it.”
The signaling from the PFC communicates with other brain areas that are needed for habit formation. These include the nucleus accumbens and the ventral tegmental area that are deeper and older. These just happen to be those reward centers we talked about that reinforce actions based on the pleasure they bring.
Dopaminergic signaling in the nucleus accumbens has a lot to do with LTP and plasticity. A 2012 study shows that dopamine in the nucleus accumbens works to reinforce strong signals while inhibiting weak ones. So burgeoning habits get reinforced and become strong habits, while changing habits is difficult because the signals to do so are inhibited. Plasticity isn’t an easy thing to induce.
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For every resolution you make, there is an unconscious resolution not to change. One reason habits (good or bad) are hard to break is because they have been successful to this point; you aren’t dead yet. Changing a habit means a journey into the unknown, and change is evolutionarily dangerous; why change what has hasn’t hurt you yet? This is why bad habits that take a long time to manifest are so insidious – like a chain-smoking 2 yr. old. |
It takes willpower to keep yourself out of those situations where bad habits are reinforced. It turns out that your willpower is a real thing, requiring energy to work and it can actually tire out. First proposed by Roy Baumeister in 1998, he showed that when people are asked to employ willpower to resist a temptation, it became harder for them to resist a later temptation. We all know this is true.
In addition, it seems that people with the best self-control use their willpower less often. A 2012 study of Wilhelm Hofmann from U. Chicago showed that people should set up their environments to minimize their temptations, so their willpower was energized for when it was really needed. If you want to stop gambling, don’t go to the track – duh!
Let’s put together all we have learned and get some tips from the experts (Peter Hall at University of Waterloo, B.J. Fogg at Stanford, and others) on how to keep your resolutions.
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Exercise affects habit formation. A 2012 study from Brazil shows that running rats on treadmills induced plasticity in the habit formation portions of the brain. Proteins and genes that control the formation and function of synapses were affected in the striatum – which includes the dopaminergic neurons of the ventral tegmental area. |
2) Focus on tiny habits that can be implemented in small doses until you can build it up to something bigger. Don’t say you will learn to play the banjo – say you will learn to play one chord. Then do it over and over.
3) Don’t just say you have intent, make the implementation concrete as well. Where and when will you practice the chord on your banjo?
4) Place your new behavior directly after a good behavior that is already a habit – you will be less likely to avoid it.
5) Reward yourself – even just a nice thought about your ability to meet your goal for that day. It will help reinforce the pathways.
6) Limit your temptations, this will help degrade the pathways that lead to the behavior you wish to change and reinforce the new pathways.
7) Get some exercise– superior prefrontal cortex function in making habits and good executive function improves with physical exercise.
Next week we can start a whole new story. If you think that you are a product of your mother and father’s genes, you are mostly right, but boy are there a lot of exceptions!
For more information, see:
NMDA receptors –
Long-term potentiation –
Neural plasticity -
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