PET scans show a boost in brain activity when addicts see images of drug usage.
“To make the drug-cues video, we worked with addicts who advised us on how to make it as realistic as possible while simulating scenes involving smoking or snorting cocaine,” said Wang. The scientists also asked the subjects to rate their level of craving while watching both videos, and assessed the severity of their addiction using a standard cocaine craving scale.
Dopamine levels were measured indirectly using positron emission tomography (PET) scanning at Brookhaven’s Center for Translational Neuroimaging. Each subject was injected with a radiotracer designed to bind to dopamine receptors in the brain. During scanning, the PET camera picks up the signal from any bound radiotracer so that levels of tracer bound to receptors can be compared with levels in the blood. As the body’s natural dopamine levels rise, this “endogenous” dopamine competes with the tracer for binding sites, so less radiotracer can bind to the receptors. Therefore, the lower the bound tracer signal, the higher the concentration of endogenous dopamine.
Compared with the neutral video, the cocaine-cues video triggered a significant increase in dopamine in the dorsal striatum, a part of the brain involved in experiencing desire or motivation. The changes in dopamine were associated with the level of craving reported by the subjects and were largest in the most severely addicted subjects.
This finding is consistent with previous animal studies that have suggested a role for the dorsal striatum in cue-induced craving. In those studies, neutral stimuli such as a particular cage environment that had been paired with a drug during “training” sessions later triggered a dopamine increase in both the nucleus accumbens and the dorsal striatum, a response that was correlated with drug-seeking behaviors in the animals.
Frustrated desires for food also cause a rise in brain dorsal striatum dopamine levels.
The finding is also consistent with earlier Brookhaven research documenting dopamine increases in the dorsal striatum induced by exposure to food (see this release). In that study, healthy subjects were allowed to observe and smell their favorite foods, but not eat them; the more the subjects desired the foods, the higher their dopamine levels went.
“Finding this same association between dorsal striatum dopamine levels and cravings for food and drugs suggests that, in the human brain, drug addiction engages the same neurobiological processes that motivate food-seeking behaviors triggered by food-conditioned cues,” Volkow said. This research suggests that compounds that could inhibit cue-induced striatal dopamine increases would be logical targets for medication development to treat cocaine addiction.
At FuturePundit’s Brain Addiction:
“These findings suggest to me that compounds which inhibit or reduce desire for cocaine might also reduce cracvings for food. A drug developed to treat coke addicts might also help people to lose weight.
“Also, since the vast bulk of us experience food cravings we non-drug addicts probably understand the cravings that drive drug addicts better than many of us realize. Obese people who look down their noses with disapproval at drug addicts ought to go look in the mirror and look at the signs that they have their own very similarly caused cravings which they can not control.
“Some day we will gain the ability to tune our desires to better align our daily behavior with our longer term goals. Research into drug addiction, obesity, and other problems with human minds will produce much more than just treatments to suppress desires for food and drugs. We will also gain the ability to mold what causes our minds to feel satisfied, frustrated, impatient, happy, and sad. People will adjust their emotional reactions to make them better able to do tedious work and to pursue longer term goals.”