An Interview with Rita Z. Goldstein, Ph.D.
…the motivation to procure drugs overpowers the drive to attain most other non-drug-related goals. In this model, we mapped the core clinical symptoms in drug addiction, including craving, or “drug wanting” to the brain mechanisms that underlie the ability to control behavior, especially in an drug-related) context. In this model we postulated that drug-addicted individuals attribute excessive importance, relevance to the drug and drug-related cues. At the same time, insufficient importance and relevance/interest is attributed to non-drug-related reinforcers, stimuli such as food or social relationships that increase the probability of a subsequent behavior….this change in importance.. would be predictive of impaired control of behavior/impulsivity.
…when drug-addicted individuals think about a hypothetical situation during which they are “under the influence,” the importance of a drug reward exceeds that of … food… they indeed may be craving the drug (or at least unable to ignore it) even when the drug is no longer pleasurable.
Our results further suggest a compromise in the ability to process the relative value of secondary non-drug-related rewards (e.g., money)…(56%) subjects demonstrated decreased sensitivity to differences between levels of abstract monetary rewards. When asked to rate seven monetary amounts ($10, $20, $50, $100, $200, $500, $1000) on a scale of 0 (not at all valuable) to 10 (most valuable), these subjects rated $10 to be equally valuable to $1000; all amounts received a rating of 10.
This result makes sense if one thinks about the desire to use drugs in drug addiction: even very small amounts of money can bring an individual closer to this goal….if the relative context of reward is compromised, the addicted individual may be more amenable to making disadvantageous decisions such as trading something of high personal value for the opportunity to get high.
Q: How does this relate to the propensity for drug relapse?
A: Our results also point to a disrupted perception of inner motivational drives (or the inability to translate perception into action), which could contribute to impairments in self-control in the drug-addicted individuals. Thus, while healthy control subjects were able to modify behavior based on the perceived relative value of a reward, drug-addicted individuals were not able to do so. This impairment may represent not only a compromise in perceiving the value of a reward, but also in utilizing this knowledge to modify behavior.
..i.e., the value of a drug stimulus is higher than all other available rewards, which are perceived as equally less important than the drug, the ability to use non-drug reinforcement to control drug-taking behavior would necessarily be compromised..
Q: What is your current thinking regarding the neural mechanisms underlying this flattened sensitivity to non-drug rewards?
A: Individuals with lesions to certain regions of [their brains] have difficulties in modifying behavior appropriately in response to altered reinforcement situations in their environment. …
We think that drug addiction may be better understood as a disorder of neural regulation.
Q: What does this work suggest in terms of clinical implications for treating drug addiction?
A: Consistent with the compulsive and chronically relapsing nature of drug addiction, our findings may help explain why efforts to control addiction through reinforcement can be compromised. …Together, these approaches may enhance the ability to control drug-taking behavior even in situations when the desire for the drug exceeds that for other rewards.