title: Increased intra-individual reaction time variability in cocaine-dependent subjects: role of cocaine-related cues.
abstract: 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.
authors: Department of Psychiatry and Behavioral Sciences, University of Texas Health Science Center at Houston, United States. Shijing.Liu@uth.tmc.edu
authors: Shijing
authors: S
authors: Liu
authors: Scott D
authors: SD
authors: Lane
authors: Joy M
authors: JM
authors: Schmitz
authors: Charles E
authors: CE
authors: Green
authors: Kathryn A
authors: KA
authors: Cunningham
authors: F Gerard
authors: FG
authors: Moeller
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D019970:Cocaine-Related Disorders / Q000150:complications / Q000503:physiopathology* / Q000523:psychology*; D003072:Cognition Disorders / Q000139:chemically induced; D003463:Cues; D005260:Female; D006801:Humans; D008297:Male; D008606:Mental Processes / Q000187:drug effects; D008875:Middle Aged; D010865:Pilot Projects; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology*; D012660:Semantics; D057190:Stroop Test; D055815:Young Adult