Transcranial direct current stimulation (tDCS) has been shown to modulate subjective craving ratings in drug dependents by modification of cortical excitability in dorsolateral prefrontal cortex (DLPFC). Given the mechanism of craving in methamphetamine (meth) users, we aimed to test whether tDCS of DLPFC could also alter self-reported craving in abstinent meth users while being exposed to meth cues. In this double-blinded, crossover, sham-controlled study, thirty two right-handed abstinent male meth users were recruited. We applied 20 min 'anodal' tDCS (2 mA) or 'sham' tDCS over right DLPFC in a random sequence while subjects performed a computerized cue-induced craving task (CICT) starting after 10 min of stimulation. Immediate craving was assessed before the stimulation, after 10 min of tDCS, and after tDCS termination by visual analog scale (VAS) of 0 to 100. Anodal tDCS of rDLPFC altered craving ratings significantly. We found a significant reduction of craving at rest in real tDCS relative to the sham condition (p = 0.016) after 10 min of stimulation. On the other hand, cue-induced VAS craving was rated significantly higher in the real condition in comparison with sham stimulation (p = 0.012). Our findings showed a state dependent effect of tDCS: while active prefrontal tDCS acutely reduced craving at rest in the abstinent meth users, it increased craving during meth-related cue exposure. These findings reflect the important role of the prefrontal cortex in both cue saliency evaluation and urge to meth consumption.
Introduction:Methamphetamine is a powerful psychostimulant that causes significant neurological impairments with long-lasting effects and has provoked serious international concerns about public health. Denial of drug abuse and drug craving are two important factors that make the diagnosis and treatment extremely challenging. Here, we present a novel and rapid noninvasive method with potential application for differentiation and monitoring methamphetamine abuse.Methods:Visual stimuli comprised a series of images with neutral and methamphetamine-related content. A total of 10 methamphetamine abusers and 10 age-gender matched controls participated in the experiments. Event-related potentials (ERPs) were recorded and compared using a time window analysis method. The ERPs were divided into 19 time windows of 100 ms with 50 ms overlaps. The area of positive sections below each window was calculated to measure the differences between the two groups.Results:Significant differences between two groups were observed from 250 to 500 ms (P300) in response to methamphetamine-related visual stimuli and 600 to 800 ms in response to neutral stimuli.Conclusion:This study presented a novel and noninvasive method based on neural correlates to discriminate healthy individuals from methamphetamine drug abusers. This method can be employed in treatment and monitoring of the methamphetamine abuse.
Background: Increasing evidence indicates that opiate users and methadone maintenance patients (MMPs) are impaired in executive control tasks and response inhibition behavior compared to healthy individuals; however, the cognitive functional difference between opiate addicts and MMPs has not been clarified. Objectives: This study employed Go/No-Go tasks to evaluate the response inhibition behavior in three groups: active opiate users, stable MMPs and healthy control subjects with negative urine analysis. Patients and Methods: In this study, 45 opiate-dependents (including opium and heroin), 50 successful methadone maintenance patients (MMPs) and 50 normal controls were recruited. These three groups were matched in terms of age, gender and education level. Each subject conducted the six variants of Go/No-Go tasks in a sequential order, after being given the instructions to respond to stimulus displayed on the screen by pressing the space bar as quickly as possible (Go stimuli) and withholding responses to other stimuli (No-Go stimuli). We used Mann-Whitney nonparametric analysis to compare the performances of opiate users, MMPs and healthy controls on Go/No-Go task scores. Results: In Go trials, opiate dependents and MMPs showed better performance than controls with lower omission errors, while in No-Go trials, opiate users and MMPs committed more errors and revealed poorer performance than the controls. No significant difference was found between opiate users and MMPs performance on Go or No-Go trials, and these groups were significantly faster than controls in response to targets on Go trials or non-targets on No-Go trials. Conclusions: Opiate users and MMPs showed significant deficits on measures of response inhibition when compared to the normal participants, while MMPs did not differ from opiate users in their ability to inhibit their response to non-targets.
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