1.3.5 Brain Plasticity & Addiction

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Specifically, dopamine reinforces the association between a particular ‘thing’ (a drug for example) and the sequence of behaviors that led to acquiring and consuming that thing. Those brain areas that were active when the drug was encountered are literally bathed in dopamine. In this way dopamine helps to associate people, places and things (and even sights and sounds and smells) with the drug.

Now, remember that NIDA saw addiction as a brain disorder because it involved functional changes to brain circuits.” Well every time the connection is made between the useful ‘thing’ (the ‘drug’ in this case) and the sequence of behaviors associated with getting it, the connection between them gets stronger.

Neuroscientists refer to this process as ‘long-term potentiation’ or LTP. LTP is a process whereby the messages between brain cells gets quicker and stronger. You can remember this with the following phrase:

Brain cells that fire together, wire together”4

The following analogy might help you to understand it in more simple terms.

Imagine the top of a mountain as your VTA (which releases the neurotransmitter dopamine) and imagine that the bottom of the mountain is your Nucleus Accumbens (which receives the dopamine). Imagine that there is a ski-run that goes between the two. This is like the reward circuit that runs between the two brain areas. As any skier will tell you, the more you ski down the exact same route, the faster it becomes. This is how brain pathways work as well. The more we use them, then the faster and stronger they become. The opposite is also true. The less we use them, the weaker they become.

LTP is the active ingredient in ‘brain plasticity’. Brain plasticity is the ability of the brain to mold itself and grow new connections in response to learning, or in response to the environment. So with addiction, learning about which things are highly rewarding, and then doing them again and again actually changes the brain’s structures.

In some scientific studies it has been shown that a single exposure to an addictive drug like cocaine can initiate the process of LTP in dopamine-releasing brain cells, particularly in the VTA (which manufactures dopamine, remember).3

This is why addicts can get a sudden ‘rush’ of excitement or anticipation when they see, hear, or smell something that reminds them of their drug. They are actually getting a big slug of dopamine because the process of LTP has strengthened the connections between the part of the brain that feels the effect of the drug – with the part of the brain that registers the environment it was taken in. The drug and the things that are associated with it have become intertwined.

In a way then, addicted people are actually more addicted to the processes, rituals and habits that are laid down and reinforced by the release of brain dopamine, than they are to the drug itself.

Of course, some people are physically addicted to drugs. But this is an entirely separate thing to addiction. Physical dependence and addiction are not the same thing. You don’t need to be physically dependent on a drug to be addicted to it. Only some drugs (like alcohol, opioids and benzodiazepines) cause physical dependence, and there are many others drugs and addictive processes like gambling that do not create physical dependence. Physical dependence is not a criterion in deciding whether a drug or behavior is addictive or not. Psychological cravings are a far more reliable indicator of the presence of addiction than physical dependence.