A newly published study in Nature by researchers at the University of North Carolina at Chapel Hill reveals that
using a combination of genetic engineering and laser technology, [they] have manipulated brain wiring responsible for reward-seeking behaviors, such as drug addiction. The work, conducted in rodent models, is the first to directly demonstrate the role of these specific connections in controlling [emphasis mine] behavior.
using a combination of genetic engineering and laser technology, [they] have manipulated brain wiring responsible for reward-seeking behaviors, such as drug addiction. The work, conducted in rodent models, is the first to directly demonstrate the role of these specific connections in controlling [emphasis mine] behavior.
The UNC study, published online on June 29, 2011, uses a cutting-edge technique called “optogenetics” to tweak the microcircuitry of the brain and then assess how those changes impact behavior. The findings suggest that therapeutics targeting the path between two critical brain regions, namely the amygdala and the nucleus accumbens, represent potential treatments for addiction and other neuropsychiatric diseases.
Interestingly, I just completed a course on the brain offered by Dr. Lee Ryan at the University of Arizona as part of the Humanities Seminars Program. During her three hour lecture with slides on decision making she illustrated the reward path of the brain as beginning in the ventral tegmental area (VTA) that is known for pumping out dopamine that is transmitted to the Nucleus Accumbens and from there to the Prefrontal Cortex. By infusing minute doses of heroin directly into the Nucleus Accumbens of a rat, researchers observed an increase in the degree of dopamine and its course from the Nucleus Accumbens to the Prefrontal Cortex. Researchers then electrically stimulated the NA and obtained similar results. (Once her slides are on line, I'll link them here to illustrate the experiment with the rats.)
The researchers also determined in work with the animal that anticipation of the reward is as good as the reward itself. This illustrates the increased likelihood that someone who is or was addicted to a substance (heroin, e.g.) or a behavior (such as gambling or binging and purging) will begin to anticipate the reward and indulge in reward seeking behavior as a result unless they have managed to learn how to modify their behavior in this example of a decision making process.
That decision-making process occurs in the Frontal Lobes of the brain where something known as the Executive Function occurs. The brain, through training the results of which can become a habit as well, weighs the pros and cons of seeking the reward and hopefully makes the decision, in this case, to reject it.
Research has shown, too, if there is damage to the orbitofrontal cortex, these behaviors to avoid reward are dampened and risk taking as well as reward seeking are increased. This damage can occur as a result of a stroke. It would seem (although I have not seen any research yet about this but intend to tap the researching skills of a friend) that starvation during anorexia or electrolyte and therefore chemical imbalance due to binging and purging, could also lead to the lessening of the positive effects of Executive Function because the brain is starving. And, of course, genetics can play a role here, too, by increasing likelihood that a person's stimulus/reward system may need balancing through, for example, behavioral modification or medication among other possibilities.
Research has shown, too, if there is damage to the orbitofrontal cortex, these behaviors to avoid reward are dampened and risk taking as well as reward seeking are increased. This damage can occur as a result of a stroke. It would seem (although I have not seen any research yet about this but intend to tap the researching skills of a friend) that starvation during anorexia or electrolyte and therefore chemical imbalance due to binging and purging, could also lead to the lessening of the positive effects of Executive Function because the brain is starving. And, of course, genetics can play a role here, too, by increasing likelihood that a person's stimulus/reward system may need balancing through, for example, behavioral modification or medication among other possibilities.
Again, the goal is to develop a habit to reject a stimulus that is harmful. The researchers in the first report mentioned above are examining ways to interrupt this reward seeking behavior, as well. For those who for whatever reason simply cannot stop that reward seeking behavior once it begins, the work by those at UNC may lead to a way to stop it.
P.S. After reading and then thinking/writing about Brain Over Binge ( Kathryn Hansen's book ) is anorexia another disease or another version of the loss of the ability of a person's executive function to govern eating behavior but in anorexia's case something goes awry in the brain's wiring so that in a perverse way starvation feels good as would a narcotic?
P.P.S. After writing the above P.S., Kathryn Hansen sent me a link to an article about the study by Dr. Walter Kaye and his colleagues that indicates those with anorexia feel less anxious when they do not eat; some sort of aberration. So in a sense starvation does feel good or at least less fear inducing........
And, another PS - Here's an article published in the New York Times on the same subject elaborating on the development of addictions and the brain receptors involved.