What happens in the brain of a compulsive drug user? What is the difference in brain function between an addict and a person who takes a drug in a controlled manner? In an attempt solve this puzzle, neurobiologists at the University of Geneva (UNIGE), Switzerland; have been looking at this difference in a rodent addiction model. They have discovered that the brain circuit connecting the decision-making region to the reward system is stronger in compulsive animals. The researchers also found that by decreasing the activity of this circuit, compulsive mice were able to regain control and that conversely, by stimulating the connection a mouse that initially remained in control became addicted. The work is published in this week’s edition of the journal Nature.
Addiction is an disease that develops in stages: it starts with the initial exposure to a substance followed by a phase where consumption remains controlled. Some individuals however will start using drugs compulsively in spite of the major negative effects it has on their lives (such as mounting debt, social isolation or incarceration). Clinical estimates suggest that only one person in five moves from controlled to compulsive use.
“We do not know why one person becomes addicted to drugs while another doesn’t,” begins Christian Lüscher, senior author and professor at the Departments of Basic and Clinical Neurosciences of the Faculty of Medicine. “But our study identifies the difference in brain function between the two behaviors.”