Publication year: 2011
Source: Addictive Behaviors, Available online 12 October 2011
Shijing Liu, Scott D. Lane, Joy M. Schmitz, Charles E. Green, Kathryn A. Cunningham, …
Neuroimaging data suggest that impaired performance on response inhibition and information processing tests in cocaine-dependent subjects is related to prefrontal and frontal cortical dysfunction and that dysfunction in these brain areas may underlie some aspects of cocaine addiction. In subjects with attention-deficit hyperactivity disorder and other psychiatric disorders, the Intra-Individual Reaction Time Variability (IIRTV) has been associated with frontal cortical dysfunction. In the present study, we evaluated IIRTV parameters in cocaine-dependent subjects vs. controls using a cocaine Stroop task. Fifty control and 123 cocaine-dependent subjects compiled from three studies completed a cocaine Stroop task. Standard deviation (SD) and coefficient of variation (CV) for reaction times (RT) were calculated for both trials with neutral and trials with cocaine-related words. The parametersmu,sigma, andtauwere calculated using an ex-Gaussian analysis employed to characterize variability in RTs. The ex-Gaussian analysis divides the RTs into normal (mu,sigma) and exponential (tau) components. Using robust regression analysis, cocaine-dependent subjects showed greater SD, CV andTauon trials with cocaine-related words compared to controls (p < 0.05). However, in trials with neutral words, there was no evidence of group differences in any IIRTV parameters (p > 0.05). The Wilcoxon matched-pairs signed-rank test showed that for cocaine-dependent subjects, both SD andtauwere larger in trials with cocaine-related words than in trials with neutral words (p < 0.05). The observation that only cocaine-related words increased IIRTV in cocaine-dependent subjects suggests that cocaine-related stimuli might disrupt information processing subserved by prefrontal and frontal cortical circuits.
Highlights
► We compare reaction time variability between controls and cocaine users. ► Cocaine users show bigger variability than controls only when cocaine cues occur. ► Cocaine cues increase variability in cocaine users but not in controls. ► This suggests that cocaine cues may disrupt information processing in cocaine users.