Those that know me fairly well know that I absolutely love studying drugs and drug addiction. I have been especially engrossed by drug addiction lately because back in high school I did not grasp that complex neural mechanisms drive drug addiction. I naively thought drug addiction was a simple issue of mind over matter or a lifestyle choice. I believed a druggie chose to be addicted to drugs and therefore could also freely choose to stop being addicted to drugs. I did not realize I was very far from the truth until I took Drugs, Brains, and Behavior with Professor Ed Yeterian and the Neural Plasticity and Behavior collaborative research seminar with Professor Melissa Glenn. Ed introduced me to the potent mesolimbic dopaminergic reward pathway and Melissa introduced me to the hypothalamic-pituitary-adrenal (HPA) antireward system. The reward and antireward systems interact to drive drug addiction. Drugs of abuse activate the reward system to produce pleasurable, positively reinforcing feelings that drive initial drug use. Reward system activity diminishes with continued drug use, but the recruitment of the antireward system continues to drive drug use to the point of drug abuse by producing negative states that act as negative reinforcement. Learning about the involvement of the reward and antireward systems in driving drug addiction made me realize that drug addiction is definitely not a personal choice.
Today in the Psychology and Neuroscience seminar, we briefly discussed about how drugs change brain connections to drive activation of the reward and antireward systems. Neuroscience and drug addiction research also proposes that brain wiring predisposes some people to become drug addicts. The BBC reported on a study that found that drug addicts and their non-addict siblings had abnormalities in the fronto-striatal systems involved with self-control, which suggested that drug addicts were “wired” for drug addiction. The non-addict siblings were also susceptible to drug addiction but may have overcame it with their different environmental influences—the differences in nurture among the siblings influenced their nature. I found this interpretation rather unconvincing. It seems to me that if the siblings had the same neural abnormalities, then the non-addict sibling should still be susceptible to drug addiction. The Telegraph reported a study on brain wiring of teenagers and drug addiction, which provided a tad more promising evidence of brain wiring predetermining drug addiction. Teenagers with decreased activity in the orbitofrontal cortex, a region involved with decision-making, were linked with drug experimentation. In the connectome sense, teenagers with fewer connections at the OFC are more likely to engage in drug behaviors (I may be taking a leap here for linking brain activity with number of connections.) My issue with this is that it seems to assume that drug experimentation directly leads to drug addiction. Indeed, drug use increases activity of the reward and antireward systems that drive drug addiction, but clearly not all drug users become drug addicts.
With such iffy evidence, I find it difficult to attribute the connectome to predisposing drug addiction. I think the connectome supports development of drug addiction because drug use influences changes in the connections, but I’m not so sure if the connectome predetermines who falls into drug addiction and who does not.
Here is the BBC: http://www.bbc.co.uk/news/health-16854593
Here is the Telegraph article: http://www.telegraph.co.uk/health/healthnews/9234689/Teenage-drink-and-drug-abuse-linked-to-brain-wiring.html