The search for the sensation of pleasure is a very powerful human instinct. When we do something pleasant, the brain strengthens the circuits to learn that we should do this more often. These connections called the reward circuit extend from the brain stem (ventral tegmental area), through the limbic or emotional system (nucleus accumbens) to the frontal cerebral cortex.
Neurotransmitters are the chemicals that the brain uses to communicate neurons with each other and transmit information. Dopamine is used primarily in the reward circuit.
Drugs alter the chemical functioning of the brain by revolutionizing this circuit by giving it much more dopamine than is produced in a normal pleasant process. This has several consequences:
- The brain tries to readjust to this excess stimulation , which can destroy the neuron, reducing the number of dopamine receptors in the neuron and increasing the number of scavengers and degraders of the same.
- This will lead to tolerance : the brain will need more and more drugs to achieve the same effect as the first time.
- But more important will be the consequences in behavior: activities that were previously pleasant will progressively stop feeling equally satisfying and interesting or motivating. Only the drug will be left to fill that void .
As the brain adapts to the presence of the drug, other brain circuits will be affected and modified. The first of these and most closely related to the reward circuit will be the memory and learning circuit. This will be in charge of creating the habit and addiction.
Learning to seek pleasure is instinctive, very strong, and resistant to forgetting. Everything that involves getting and administering the drug will be strongly permeated in the brain, making it automatic, compulsive, and unconscious.
This conditioning of behavior can last for many years causing some stimulus (or memory) to lead someone to desire drugs after a long time of abstinence.
In addition, changes will progressively occur in the areas essential for judgment, decision-making, and behavior control . The consequences of these frontal lobe changes will be especially damaging in adolescents who are still developing these structures, and drugs will interfere with their normal development.
Georgina Vinyes Junqué is a member of Saluspot and a specialist in clinical neuropsychology and neurosciences.
