SCIENCE OF ADDICTION

Symptoms

Devastating changes in behavior where even under threat of the most severe of punishments, one cannot stop using the substance.

Affected area of the Brain

THE REWARD CENTER is the most primitive part of our brain (ancient lizards had this part of the brain). It tells you every day to find food, find clean water and find a mate; because your only real job on this planet from an evolutionary standpoint is to survive long enough to procreate. The drive you have to engage in these behaviors is mediated by the neurotransmitter dopamine; without it, you die. The problem: it’s this “am going to live today, or am I going to die today?” part of the brain that is impacted by every substance of abuse.

1) Relevance of Dopamine

When we engage in pleasurable behavior, spikes in dopamine occur. These spikes positively reinforce us to continue these behaviors.

An example of how this works is shown in the diagram at the right. Most of us have a baseline dopamine level of “100” against which we measure increases and decreases. If you get your perfect food item your dopamine will spike to 150 and return right back to baseline. It is an evolutionary intention that our dopamine is elevated; this positively reinforces pleasurable behavior such as eating, having sex or listening to music and incites our brains to form powerful memories of them.

2) Substances of Abuse Raise 

     Dopamine to Abnormal Levels

Substances of abuse raise our dopamine much higher than natural reinforcers.

Some substances of abuse raise dopamine as much as 5-6 times higher than natural reinforcers (as the graph on the right shows). When this happens, the reward center in our brain recognizes it as terribly wrong and immediately strives to correct it.

3) How the Brain Responds to Abnormal

     Levels of Dopamine

As mentioned above, there are three main ways that our brains regulate dopamine:

• how much dopamine it releases
• how many receptors are able to receive the dopamine
• and how much dopamine it will reabsorb/degrade

When the brain experiences abnormally high levels of dopamine it will:

burn up 80% of receptors

Let’s Graph this out

Remember the healthy brain:

It wakes up with baseline dopamine of 100, it gets its favorite food item, it spikes to 150 and then comes back to baseline

The brain developing addiction:

It gets its first drug high, say 900 with heroin, and with repeated administration, it doesn’t get to 900 again, it may get to 880 then 850, 800, etc. But the real problem isn’t that the person isn’t reaching previous high levels of dopamine. The problem is that when that person wakes up in the morning, they are no longer at baseline 100… their baseline bottoms out, and they wake up at dopamine levels of maybe 30 or 40.

The Reward Center of the Brain isn’t the Only Target!

The prefrontal cortex is highly dependent on dopamine for proper functioning. A small list of functions are:

• ability to plan ahead
• predicting consequences
• impulse control
• coordinating complex behaviors (I can’t do “X” before “Y” happens)

All executive functioning relies on the proper functioning of the prefrontal cortex. Its ability to function is dependent on dopamine; so while the disruption to the reward center explains why there is an intense drive to seek out the desired drug to raise dopamine, the deprivation of dopamine to the PFC explains why reasoning and logic cannot appeal to the person suffering SUD.