Biology concepts – learning, habit, long term potentiation, neural plasticity
this year I’m going to get these posts written a month in advance. Really, I mean it this time. I know I said the same thing last year, but this time I’ve got a plan in place –- yeah, sure. Biology is stacked against me here; making new good habits is definitely an exception. Our brains function to make it hard to change our behaviors – but it is possible.
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.
The philosopher and psychologist William James said, “99% of our behavior is purely automatic ….. all of our life is nothing but a mass of habits.” This is mostly true, we need to save our thinking for things that are important and undetermined, not for everyday things for which we can easily predict the outcomes and do not threaten our existence. You don’t think about putting one foot in front of the other when you walk, you look for the bus that may stop you dead in your
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 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.
receptors in question work with dopaminergic neurons are there to reinforce signals and strengthen nerve firing. They are called NMDA receptors, and they respond to glutamate, an amino acid and important neurotransmitter. In the synapses (gaps, Greek; syn = together, and haptein = junction) between neurons, NMDA receptors bind glutamate and then allow sodium and calcium into the downstream neuron. These work in different ways to make the firing of the neuron stronger. Calcium in particular can keep the upstream neuron firing and keep stimulating the down-stream neuron. This leads to long-term potentiation (LTP).
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 , 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.
prefrontal cortex is more than just the SPFC. showed that the ventromedial prefrontal cortex is important in self-control, while the dorsolateral prefrontal cortexis important in meeting goals. And we all know that we need some hefty self-control to keep resolutions.
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 . 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.
reason habits are hard to break is the reinforcers; those things that trigger the behavior are a part of our everyday lives. You need to stay away from these reinforcers (temptations might be a better word) because your brain remembers those reinforcers for a long time. It stores the contexts in which the habits are triggered and can bring back the behavior of the context is encountered again. It takes time for plasticity to weaken these pathways.
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 , 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 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.
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?
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!
Wang, L., Li, F., Wang, D., Xie, K., Wang, D., Shen, X., & Tsien, J. (2011). NMDA Receptors in Dopaminergic Neurons Are Crucial for Habit Learning Neuron, 72 (6), 1055-1066 DOI: 10.1016/j.neuron.2011.10.019
Wang, W., Dever, D., Lowe, J., Storey, G., Bhansali, A., Eck, E., Nitulescu, I., Weimer, J., & Bamford, N. (2012). Regulation of prefrontal excitatory neurotransmission by dopamine in the nucleus accumbens core The Journal of Physiology, 590 (16), 3743-3769 DOI: 10.1113/jphysiol.2012.235200
For more information, see:
NMDA receptors –
Long-term potentiation –
Neural plasticity -http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=10&ved=0CG8QFjAJ&url=http%3A%2F%2Fwww.acnp.org%2Fasset.axd%3Fid%3D852ca1c4-ece9-4f2b-988d-bd6b5222e5ac&ei=9Ty-UKeYM9S80QHLtYHgBQ&usg=AFQjCNER4QfEVPqNhq6jrFAXfcQE4DVN_A