Cocaine Users Show Reduced Ability To Enjoy Rewards

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http://www.scienceofwonder.org/cocaine-users-show-reduced-ability-to-enjoy-rewards/

A new study intothe brain activity of cocaine-dependent individuals has suggested that their ability to appropriately anticipate and enjoy rewards may be disrupted, resulting in a greater propensity to engage in risky behavior. Aside from providing an insight into the impulses that drive addictive tendencies, the findings also indicate that those who habitually use drugs may also be more likely to act recklessly in other areas of life.

Several previous studies have shown that drug addicts often have a greater thrill-seeking drive than the general population due to a high level of anhedonia, which refers to a blunted sense of enjoyment in everyday situations. As a consequence, they may feel the need to go to more extreme lengths in order to gain a sense of satisfaction in life, often leading them into cycles of destructive behaviors.

To examine the ways in which this character trait is represented in brain activity, researchers asked 23 active cocaine users and 23 non-users to complete a questionnaire designed to analyze their levels of anhedonia. After analyzing the results, the study authors noted that cocaine users scored significantly higher for anhedonia-related characteristics than non-users.

Participants then took part in a challenge in which they won or lost gift vouchers depending on the speed at which they were able to react to a visual cue. Before each repetition of the task, they were presented with a colored disk representing the probability of receiving a large, small or neutral reward or penalty.

Using an electroencephalograph, the researchers recorded the electrical response of participants brains called event-related potentials (ERP) at each stage of the process, looking for particular signals that have previously been associated with the anticipation and enjoyment of rewards.

For instance, immediately prior to each new challenge, researchers examined a component of participants ERPs known as the contingent negative variation (CNV), which is thought to provide a measure of motivation to perform a task. Two signals called the P2 and the P300, both of which are associated with reward prediction, were then measured once participants received information regarding their chances of winning.

Finally, a component called the feedback-related negativity (FRN), which is thought to be implicated with processing received rewards, was examined after participants found out whether they had won or lost.

Despite higher levels of anticipation and motivation, cocaine addicts experienced less enjoyment after receiving rewards. sondem/Shutterstock

A significantly greater CNV amplitude in cocaine users compared to non-users suggests that this group experienced an enhanced sense of anticipation prior to taking the challenge, and were more motivated to obtain an award. Interestingly, however, the P2 and P300 response was much smaller in the cocaine-using group once their chances of winning were revealed, indicating an inability to make accurate reward predictions and adapt their behavior accordingly. This, the researchers suggest, may contribute to the inability of addicts to stop using drugs despite knowing from experience that the outcome will not be as rewarding as they hope.

Furthermore, upon completion of the task, cocaine users displayed diminished FRNs compared to non-users, indicating a lack of satisfaction when gift vouchers were obtained, or disappointment when these were lost.

Presenting their findings in the journal Psychopharmacology, the study authors conclude that cocaine use is associated with a dysregulation between wanting rewards and liking rewards,as well as an ability to properly monitor actions taken to receive reward or update reward predictions.

In other words, drug addicts experience unusually high levels of reward anticipation but dampened enjoyment upon obtaining these rewards, which may be a major driver of their excessive desire to use drugs. As such, the researchers suggest that anhedonia may be a key marker of a persons vulnerability to addiction.

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