A wonder of the human brain is its capacity to fundamentally remodel and reorganize its structure and function – what scientists call neuroplasticity. Plasticity, in this context, means malleability, or the ability to bend and adjust, while neuro– means anything to do with the nervous system or brain.
In response to brain damage, to learning a new skill, or to environmental pressures for adjustment, the human brain has the capacity to make new maps and new circuits of communication among and between the estimated one hundred billion cells – called neurons – that it contains.
The more often neurons fire together – the repeated chemical messaging that underlies and generates behavior – the more circuits wire together. When circuits wire together, habitual behaviors form.
Think of a city park, cleared from a dense thicket of woods, then ordered into clearings and paths for public use. That’s a helpful way to visualize the modeling and organizing that happens in the brain that we call neuroplasticity. It takes lots of pruning and clearing, but eventually what we have is a nice park that everyone can use.
In the case of the brain, neurons are what’s cleared and pruned, not trees and bushes. Neurons form the circuits and paths of the central nervous system. These circuits, in turn, form the foundation of our behavior, including all our habits and skills.
Our neural circuitry is part of what makes us who we are. It takes time to prune and clear all the neurons, but eventually what we have is a human being with an entire set of behaviors and personality traits unique to them.
Let’s get back to that park image.
If a thunderstorm crashes an enormous tree into an established path, or flooding erodes an often-used walkway, then remodeling and reorganizing are required to establish new paths around the damage to restore the ability to navigate the park.
Neuroplasticity allows the brain to perform just this sort of restorative activity.
When brain circuits or tissue become damaged – think of addiction as a storm that crashes trees and erodes pathways – the brain has the ability to repair itself. It does this through remodeling and reorganizing, rewiring, or, more simply, through neuroplasticity.
The repaired function may not be identical to the original function, but in many cases it’s functionally indistinguishable. For people with brain damage from trauma or stroke, this is encouraging.
For people in recovery from alcohol or substance use disorders, it’s promising.
And for scientists – particularly those who study addiction – it’s intriguing.
Drugs of Misuse and the Brain
Over the past 30 years, neuroscientists have theorized – and the medical and scientific communities have accepted – that addiction is a disease of the brain. An individual with an alcohol or substance use disorder enters a negative, destructive cycle because not only do the drugs damage their brain, but the ensuing damage causes them to continue to seek out alcohol or drugs despite serious ongoing harm.
Part of what makes drug-seeking behavior so damaging is that it can override more basic needs, such as food or sleep. To complicate the matter further, when a person with an alcohol or substance use disorder enters a period of abstinence or recovery, structural changes in the brain increase likelihood of relapse.
Scientists have begun to understand how different classes of drugs – whether methamphetamine, cocaine, heroin, or alcohol – produce different neuroadaptations. While each substance seems to affect the same region of the brain – the mesolimbic system, which is associated with pleasure, planning, reward, and self-directed learning/training – the specific damage it does to this system varies for each substance.
The molecule crucial to reinforcing and rewarding behaviors so that they become habitual behaviors is called dopamine. Dopamine transmission in the brain also signals that a given stimulus leads to a reward, thereby motivating an individual to seek it out.
Dopamine release, in general, makes individuals alert and seek stimuli that produce pleasure. This happens directly, by stimulation of the mesolimbic system, or indirectly, through the generation of goal-directed behaviors that lead to reward.
For instance, dopamine is the molecule involved in motivating an individual to study hard in school in order to earn excellent grades, or put in extra hours of soccer practice in order to score a goal during a game.
Opioids and Plasticity
Take opioids, for example – a class of drug that can damage the brain. Opioid use can reduce the number of active dopaminergic neurons, which then drastically reduces the rate of dopamine release. The impact of this neuroplastic event is that the brain does not adequately reward and reinforce behavior that previously brought pleasure. In this case, the brain’s neuroplasticity works against itself: the brain’s capacity for pleasure is diminished – or rewired – by prolonged opioid use.
The same happens with virtually all drugs of misuse. While the precise neurons affected may vary from substance to substance, the result is a neuroplastic rewiring of the brain’s reward system, which can and does lead to behavior that is unhealthy and counterproductive.
When viewed in this way, alcohol and substance use disorders can be considered diseases of neuroplasticity.
Rewiring for Recovery
The fact that prolonged exposure to substances of misuse remodels the brain is not the end of the story. In fact, the story of neuroplasticity has a promising ending because in it, the brain is equipped to repair the damage that can result from addiction.
Successful treatments for alcohol and substance use disorders involve therapies and activities that engage the brain in restorative rewiring. Some of those treatments, depending on the drug of misuse, may be medications. Other treatments can involve specialized psychotherapy that helps the brain rewrite the neuroplastic changes of prolonged exposure to substances of misuse.
Currently, neuroscientists are seeking treatments that disrupt the circuits that lead to relapse, some of which remain in place for years after an individual enters treatment and begins recovery.
Relapse is an ongoing concern because environmental cues associated with substances of misuse can – even after long periods of abstinence – stimulate drug-seeking behavior. Treatments that can effectively break those associations may be the key to reducing overall rates of relapse for people living with alcohol and substance use disorders.
The phenomenon of neuroplasticity implies that long-term, successful recovery from alcohol and substance use disorders is within reach, as long as we seek treatments that repair addiction-related dysfunction and help rewire the brain to reinforce healthy and productive habits – ones that bring pleasure and reward without causing physical, emotional, and psychological harm.