A new study has indicated that long-term cocaine use may produce changes to the parts of the brain responsible for regulating impulsivity and the ability to analyze the significance of one’s decisions. Not only do these alterations provide an insight into what drives addiction, but they also suggest that those who develop a dependence on the drug may be liable to make poor decisions in other areas of life too.
To conduct their study, researchers recruited 30 cocaine-dependent subjects – all of whom were abstinent at the time of the experiment – to take part in a gambling exercise, in which they won or lost money depending on their ability to guess which number would appear on a screen. Using various imaging techniques, the study authors were able to measure activity alongside tissue volume and microstructure in the brains of participants.
Presenting their findings in the journal Addiction Biology, they note that, compared to non-users, cocaine-dependent individuals displayed increased activity in the ventral striatum, which forms part of the brain’s reward circuit. Importantly, activity in this region was found to be elevated regardless of whether the individual won or lost the gambling challenge, indicating that negative outcomes do not dampen the individual’s desire to seek out the rewards associated with a particular activity – in this case gambling. Accordingly, several previous studies have hypothesized that hyperactivity in the reward circuit may be a major driver of addiction.
On top of this, the researchers found abnormal patterns of activity in parts of the medial prefrontal cortex in cocaine users. This applied particularly to the areas encompassing the anterior cingulate cortex and orbitofrontal cortex, both of which are associated with assessing the outcomes of one’s decisions, attributing salience to these outcomes, performance monitoring and the encoding of reward and punishment signals.
As expected, when the gambling task was performed by non-cocaine users, losses resulted in a robust increase in activation in these brain regions, enabling them to assess and analyze their behavior and respond accordingly. However, no such activation was noted in the cocaine users, suggesting that their ability to appreciate the consequences of their decisions may be impaired.
These functional changes were found to correlate with structural abnormalities in these same brain regions. For instance, increased grey matter volumes were observed in parts of the reward circuit, such as the caudate nucleus.
While it is not yet known how much cocaine a person has to take before these effects are produced – or, indeed, if they can be reversed – the study provides a fascinating and useful insight into the structural and functional changes that repeated use of the drug generates in the brain.
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