Increased intra-individual reaction time variability in cocaine-dependent subjects: Role of cocaine-related cues

Shijing Liu, Scott D. Lane, Joy M. Schmitz, Charles E. Green, Kathryn A. Cunningham, F. Gerard Moeller

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


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 parameters mu, sigma, and tau were 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 and Tau on 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 and tau were 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.

Original languageEnglish (US)
Pages (from-to)193-197
Number of pages5
JournalAddictive Behaviors
Issue number2
StatePublished - Feb 2012
Externally publishedYes


  • Cocaine Stroop task
  • Cocaine dependence
  • Ex-Gaussian analysis
  • Intra-individual reaction time variability

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Clinical Psychology
  • Toxicology
  • Psychiatry and Mental health


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