Individuals with cocaine use disorder or gambling disorder demonstrate impairments in cognitive flexibility: the ability to adapt to changes in the environment. Flexibility is commonly assessed in a laboratory setting using probabilistic reversal learning, which involves reinforcement learning, the process by which feedback from the environment is used to adjust behavior.

It is poorly understood whether impairments in flexibility differ between individuals with cocaine use and gambling disorders, and how this is instantiated by the brain. We applied computational modelling methods to gain a deeper mechanistic explanation of the latent processes underlying cognitive flexibility across two disorders of compulsivity.

We present a re-analysis of probabilistic reversal data from individuals with either gambling disorder (n = 18) or cocaine use disorder (n = 20) and control participants (n = 18), using a hierarchical Bayesian approach. Furthermore, we relate behavioural findings to their underlying neural substrates through an analysis of task-based functional magnetic resonanceimaging (fMRI) data.

We observed lower ‘stimulus stickiness’ in gambling disorder, and report differences in tracking expected values in individuals with gambling disorder compared to controls, with greater activity during reward expected value tracking in the cingulate gyrus and amygdala. In cocaine use disorder, we observed lower responses to positive punishment prediction errors and greater activity following negative punishment prediction errors in the superior frontal gyrus compared to controls.

Using a computational approach, we show that individuals with gambling disorder and cocaine use disorder differed in their perseverative tendencies and in how they tracked value neurally, which has implications for psychiatric classification.

Almost all definitions of impulsivity include the notion of distorted time perception such as impaired awareness of the future or premature responses. Preclinical evidence suggests that stimulant drugs speed up the internal clock, making time pass faster than it actually is. However, stimulant-addicted humans, who are drug-abstinent seem to over-estimate long time intervals.

The present study aims to investigate time processing in actively using patients with cocaine use disorder (CUD). We hypothesise that active cocaine use will be associated with an under-estimation of long time intervals.

We recruited 48 men with a chronic history of cocaine use, meeting the DSM-5 criteria for CUD, and 42 healthy men without a history of substance use disorders. All participants completed a time reproduction task in which they were presented four times with six different time durations and were subsequently asked to reproduce them by pressing the space bar for the same time duration of the target interval they had just seen. Participants also completed the Barratt Impulsiveness Scale (BIS-11).

Overall precision in time reproduction was significantly reduced in CUD patients (F6,81=3.97,p=0.002), which was particularly evident for longer time delays. CUD patients’ estimated-to-target-duration ratios were marginally shorter for the 11000ms (F1,86=3.1,p=0.084) and significantly shorter for the 18000ms and 24000ms time intervals (both p<0.05). Time reproduction performance correlated with self-reported attentional impulsivity on the BIS-11 in both CUD patients and healthy controls (all p<0.05).

Consistent with preclinical work, the inner clock of humans with regular cocaine use seems to be accelerated.

No significant relationships.