The Effects of Dopamine on the Reward-Learning Pathway

Addiction is a chronic brain disease in which an individual compulsively uses mind-altering substances despite the many adverse, harmful consequences. Just as cardiovascular disease damages the heart and diabetes impacts the liver, addiction, too, disrupts activity in the body. However, unlike other diseases, addiction substantially affects the brain – making it one of the deadliest diseases in the U.S.

Because of this, the American Society of Addiction Medicine and other medical associations didn’t hesitate when defining addiction as a disease rather than a moral failing or a lifestyle choice. Research shows that addiction alters brain activity, specifically the regions that control reward, memory, learning, and compulsion.

So How Does Addiction Work?

To better understand this complex disease, let’s dive into the neurobiology of addiction. Specifically, the Reward-Learning Pathway.

The Reward-Learning Pathway

The reward pathway is made up of three components:

1. Initial pleasure
2. The learning process
3. Compulsion and tolerance

Initial Pleasure

Pleasure – whether elicited by gambling, sex, food, music, or psychoactive drug – is characterized by a release of dopamine, a naturally-occurring neurotransmitter in the brain. That “feel good” effect is caused by a surge of this neurotransmitter and stimulates self-reinforcing behavior of wanting more.

At an anatomical level, this reward system (i.e. the mesolimbic dopamine pathway) is comprised of neurons extending from the ventral tegmental area (VTA) to the nucleus accumbens (NAc). When these pathways are activated by natural rewards, the concentration of dopamine increases, and one feels a pleasurable, energizing stimulus.

No doubt, this electrifying pathway is at the heart of addiction. Even The Sun took it so far as to report that “cupcakes could be as addictive as cocaine” due to their ability to cause spikes in dopamine levels.

Although written to incite frenzy, there is some truth in it. Addictive drugs like heroin, cocaine, or meth cause powerful surges of dopamine in the brain.

It’s this dangerous surge of dopamine that can lead to addiction. Researchers at Harvard suggest that the likelihood of addiction is determined by (a) the speed at which the drug promotes dopamine release as well as (b) the intensity and (c) reliability of that release. In essence, smoking or injecting a drug intravenously is more likely to lead to abuse as compared to swallowing a pill since this mechanism produces a stronger, quicker spike in dopamine levels.

The Memory / Learning Process

In addition to making us feel good, dopaminergic reward pathways also ensure we repeat pleasurable behavior – an adaptive trait for survival (i.e. sex, eating). This is done through the help of dopamine’s interaction with glutamate, a neurotransmitter responsible for an organism’s adaptive behavior to a changing environment. Glutamate is responsible for reward-related learning due to its activity in memory and motivation.

For instance, if I remember that eating a cheeseburger made me feel good, I’m more inclined to eat one again. By recalling the taste of the fresh patty… the smell and feel of that hot, buttery bun… or how juicy the tomatoes felt as their flavor slowly permeated across my palate with each zesty bite… In essence, I’m strengthening the connections of this reward loop all the while increasing my likelihood for repeating this action in the future.

Ultimately, activation of pleasure centers in our brain, in turn, affect our behavior. When we use addictive substances, we are altering our brain chemistry and creating what is known as a motivational property (i.e. a desire, craving, or wanting for a reward). We go from simply liking something to wanting it as we are now motivated to seek out that stimulus again.

The Compulsion / Tolerance Pathway

Over time, the consistently high levels of dopamine desensitize neurons and decrease the amount of dopamine receptors in the brain. As a result of this adaptation, the pleasure originally felt by the rush of dopamine is dampened – an effect known as tolerance. Unfortunately, the desire to obtain this same high still exists.

This is when we see compulsion. Despite the lessened dopamine response, the memory of that “feel good” effect remains and the desire to recreate it greatens. From this comes cravings and an increase in the potential for relapse.

At Stonegate Center, we understand the difficulties associated around drug and alcohol addiction and are aware of the Reward-Learning Pathway in the brain. If you feel like you are stuck in an endless loop, give us a call at (817) 993-9733. Our program is designed to help you understand how your brain works, how it reacts to illicit substances, and what you can do to overcome those mental roadblocks to recovery.