Abstract
Methamphetamine (MA) dependence is associated with cognitive deficits. Methylphenidate (MPH) has been shown to improve inhibitory control in healthy and cocaine-dependent subjects. This study aimed to understand the neurophysiological effects before and after acute MPH administration in active MA-dependent and control subjects. Fifteen MA-dependent and 18 control subjects aged 18–46 years were scanned using functional magnetic resonance imaging before and after either a single oral dose of MPH (18 mg) or placebo while performing a color-word Stroop task. Baseline accuracy was lower (p = 0.026) and response time (RT) was longer (p < 0.0001) for the incongruent compared to congruent condition, demonstrating the task probed cognitive control. Increased activation of the dorsolateral prefrontal cortex (DLPFC) and parietal cortex during the incongruent and Stroop effect conditions, respectively was observed in MA-dependent compared to control subjects (p < 0.05), suggesting the need to recruit neural resources within these regions for conflict resolution. Post- compared to pre-MPH treatment, increased RT and DLPFC activation for the Stroop effect were observed in MA-dependent subjects (p < 0.05). In comparison to MPH-treated controls and placebo-treated MA-dependent subjects, MPH-treated MA-dependent subjects showed decreased activation of parietal and occipital regions during the incongruent and Stroop effect conditions (p < 0.05). These findings suggest that in MA-dependent subjects, MPH facilitated increased recruitment of the DLPFC for Stroop conflict resolution, and a decreased need for recruitment of neural resources in parietal and occipital regions compared to the other groups, while maintaining a comparable level of task performance to that achieved pre-drug administration. Due to the small sample size, the results from this study are preliminary; however, they inform us about the effects of MPH on the neural correlates of cognitive control in active MA-dependent subjects.
Highlights
Methamphetamine (MA) dependence is a global public health problem, with a consumer market of between 15 and 16 million people in 2007 [1]
In comparison to “control MPH” and “MA placebo” subjects,“MA MPH” subjects exhibited decreases in Functional magnetic resonance imaging (fMRI) activation of parietal and occipital regions, which were thought to be necessary for Stroop conflict resolution prior to drug treatment
To the best of our knowledge, this is the first fMRI study to investigate the effect of MPH on cognitive control in active MAdependent subjects in comparison to control subjects
Summary
Methamphetamine (MA) dependence is a global public health problem, with a consumer market of between 15 and 16 million people in 2007 [1]. Impairment of cognitive control, or top-down processing, is thought to be essential in the transition from casual and voluntary drug use to drug dependence in humans [5, 23,24,25]. While separable, are integrally related and include: task switching, reward-based learning, performance monitoring, and conflict resolution [22]. The latter includes response inhibition, and the ability to inhibit a prepotent automated response in favor of a less familiar task-relevant response [22, 26]. A common measure of this type of response inhibition is the color-word Stroop task [26], which is the focus of the current study
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
