Leading-edge technologies let researchers study the brain’s response to stimuli in ways not previously possible – and open paths to treating addiction.
If you love dessert, the smell of a warm apple pie will make you stop and look for the source. Your mouth might water at the anticipation of that first sweet bite. But what if you had that strong reaction to seeing a syringe full of heroin? The impulses we experience and yield to when we smell fresh apple pie are the same impulses that someone addicted to heroin experiences when they see the drug.
Dr. Susan Ferguson studies the brain circuits associated with addiction, reward, decision-making, motivation and impulsivity. In 2015, her lab made leaps in understanding how addiction and impulse control disorders play out in different regions of the brain. Looking ahead, they hope the work will lead to better ways to identify and effectively treat these life-altering conditions.
Her study in Neuropsychopharmacology found that dampening the connection between two key brain regions associated with reward in rat models – the prefrontal cortex and the nucleus accumbens – resulted in fewer addictive behaviors.
“The connection between the prefrontal cortex and the nucleus accumbens links the drug to the experience,” Ferguson says. “When addicts see drug cues, the prefrontal cortex becomes very active. It’s likely that this activity triggers the desire to use the drug, leading to relapse. This research expands our understanding of how to control addictive behavior and could lead to therapies that target the parts of the brain where addictive associations are made.”
In 2015, Ferguson’s team also found that turning down activity from the prefrontal cortex to the striatum decreased the incidence of relapse in rats exposed to drugs.
Brains of addicts differ
“About 10% to 15% of people who try drugs will become addicts and regular users,” says Ferguson, who notes that research suggests addicts’ brains differ from typical brains and that part of the broader goal of addiction research is understanding what the brains of addicts are like at baseline before they try drugs – and if drugs affect their brains differently than those of others.
“From a practical standpoint, we want to be able to identify people who are prone to addiction so early interventions can be made. This is crucial for kids because young people who become addicted are the hardest patients to treat,” she notes. “We need to catch the signs early and have therapies that target the parts of the brain responsible for addiction.”
Ferguson and her team are using new technologies that provide unprecedented precision in monitoring and controlling regions of the brain in rodent models. One technology (called optogenetics) is rooted in light and the other (called chemogenetics) in drugs. By modifying the neurons to be light or drug sensitive, the team uses light and small molecules to observe how the brain reacts to stimuli.
These technologies allow the team to examine the involvement of brain circuits at a level of detail that has not been possible in the past.
The level of precision to target neurons and regions of the brain has Ferguson hopeful that treatments for addiction and impulse control disorders can be fine-tuned someday. She thinks that some promising drugs might already be on the market, but they need to be modified to target fewer brain areas.
“Some patients who take medication for impulse control disorders stop their treatment because the drugs affect the entire brain and mood, not just the region of the brain responsible for the disorder,” Ferguson says. “If we can develop more tailored therapies, patients will be more likely to stick with them.
“If we can help a young person avoid becoming an addict or develop a drug that can help a child manage an impulse control disorder, we change the course of that person’s life.”
This research will help us develop therapies that target parts of the brain where addictive associations are made.
– Dr. Susan Ferguson