Modulation of risk-taking in marijuana users by transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex (DLPFC)
Cognitive deficits that are reported in heavy marijuana users (attention, memory, affect perception, decision-making) appear to be completely reversible after a prolonged abstinence period of about 28 days. However, it remains unclear whether the reversibility of these cognitive deficits indicates that (1) chronic marijuana use is not associated with long-lasting changes in cortical networks or (2) that such changes occur but the brain adapts to and compensates for the drug-induced changes. Therefore, we examined whether chronic marijuana smokers would demonstrate a differential pattern of response in comparison to healthy volunteers on a decision-making paradigm (Risk Task) while undergoing sham or active transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex (DLPFC). Twenty-five chronic marijuana users who were abstinent for at least 24h were randomly assigned to receive left anodal/right cathodal tDCS of DLPFC (n=8), right anodal/left cathodal tDCS of DLPFC (n=9), or sham stimulation (n=8); results on Risk Task during sham/active tDCS were compared to healthy volunteers from a previously published dataset. Chronic marijuana users demonstrated more conservative (i.e. less risky) decision-making during sham stimulation. While right anodal stimulation of the DLPFC enhanced conservative decision-making in healthy volunteers, both right anodal and left anodal DLPFC stimulation increased the propensity for risk-taking in marijuana users. These findings reveal alterations in the decision-making neural networks among chronic marijuana users. Finally, we also assessed the effects of tDCS on marijuana craving and observed that right anodal/left cathodal tDCS of DLPFC is significantly associated with a diminished craving for marijuana.
[Show abstract] [Hide abstract] ABSTRACT: transcranial Direct Current Stimulation (tDCS) over the dorsolateral prefrontal cortex (dlPFC) has been shown to be clinically useful in the treatment of drug addiction. We conducted a double-blind randomized clinical trial aiming to assess the effects of bilateral dlPFC tDCS (left cathodal/right anodal) on crack-cocaine addiction. We defined craving as the primary outcome, and other clinical measurements, including depressive and anxiety symtoms, and quality of life, as secondary outcomes. 17 male crack-cocaine users (mean age 30.4 ± 9.8 SD) were randomized to receive five sessions of active tDCS (2 mA, 35 cm(2), for 20 minutes), every other day, and 19 males (mean age 30.3 ± 8.4 SD) to receive sham-tDCS (placebo), as control group. Craving scores were significantly reduced in the tDCS group after treatment when compared to sham-tDCS (p = 0.028) and to baseline values (p = 0.003), and decreased linearly over four weeks (before, during and after treatment) in the tDCS group only (p = 0.047). Changes of anxiety scores towards increase in the sham-tDCS and decrease in the tDCS group (p = 0.03), and of the overall perception of quality of life (p = 0.031) and of health (p = 0.048) towards decrease in the sham-tDCS group and increase in the tDCS group, differed significantly between groups. Repetitive bilateral tDCS over the dlPFC reduced craving to crack-cocaine use, decreased anxiety and improved quality of life. We hypothesize that tDCS effects may be associated with increased pre-frontal processing and regulation of craving behavior. © The Author 2015. Published by Oxford University Press on behalf of CINP.
- "Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that induces polarity-dependent alterations of cortical excitability (Nitsche and Paulus, 2000; Nitsche et al., 2003 Nitsche et al., , 2007 Nitsche et al., , 2008). Modulation of dlPFC functions with tDCS has been shown to reduce craving for smoking (Fregni et al., 2008a), marijuana (Boggio et al., 2010), and food in healthy subjects (Fregni et al., 2008b). We thus hypothesized that tDCS over the dlPFC might be a promising therapeutic approach to treat drug dependence. "
[Show abstract] [Hide abstract] ABSTRACT: Addiction is a chronic relapsing brain disease with significant economical and medical burden on the societies but with limited effectiveness in the available treatment options. Better understanding of the chemical, neuronal, regional, and network alterations of the brain due to drug abuse can ultimately lead to tailoring individualized and more effective interventions. To this end, employing new assessment and intervention procedures seems crucial. Noninvasive brain stimulation (NIBS) techniques including transcranial electrical and magnetic stimulations (tES and TMS) have provided promising opportunities for the addiction medicine in two main domains: (1) providing new insights into neurochemical and neural circuit changes in the human brain cortex and (2) understanding the role of different brain regions by using NIBS and modulating cognitive functions, such as drug craving, risky decision making, inhibitory control and executive functions to obtain specific treatment outcomes. In spite of preliminary positive results, there are several open questions, which need to be addressed before routine clinical utilization of NIBS techniques in addiction to medicine, such as how to account for interindividual differences, define optimal cognitive and neural targets, optimize stimulation protocols, and integrate NIBS with other therapeutic methods. Therefore, in this chapter we revise the available literature on the use of NIBS (TMS and tES) in the diagnostic, prognostic, and therapeutic aspects of the addiction medicine.
- "6. Defining objectively the monitoring measures: As it can be seen in Tables 2 and 3, drug craving is the most common cognitive target and assessment measure in addiction and NIBS studies. However, there is an increasing trend for targeting other components including risk-taking behavior (Boggio et al., 2010;Fecteau et al., 2014;Gorini et al., 2014), relapse (daSilva et al., 2013;Klauss et al., 2014), drug consumption (Boggio et al., 2009;Fecteau et al., 2014;Meng et al., 2014), and attentional bias (Meng et al., 2014). Self-report questionnaires are subjective, and therefore prone to risk of assessment bias. "
[Show abstract] [Hide abstract] ABSTRACT: To test the intra-individual reliability in response to anodal transcranial direct current stimulation (AtDCS). 45 healthy subjects received AtDCS (1mA, 13min) in two separate sessions, 6-12months apart. Motor evoked potentials were collected at baseline and then at 5-min intervals after AtDCS for 1h. Short intracortical inhibition (SICI) was assessed at minutes 6 and 46 after AtDCS. AtDCS increased cortical excitability over minutes 0-30 post-stimulation in both sessions, with fair intra-individual reliability. 60% and 64% of subjects responded with the expected increase in cortical excitability in each session, respectively. 69% of the subjects maintained their response pattern between sessions during this timeframe. However, there were no significant effects on cortical excitability over the full hour post AtDCS in either session. SICI showed fair intra-individual reliability 6min after AtDCS. A change in cortical excitability in the first half-hour post-AtDCS may be a good predictor of the response in a subsequent session. Furthermore, minute 15 post-stimulation showed the maximum increase in cortical excitability in both sessions. We show for the first time that intra-individual variability is lower than inter-individual variability, and with fair intra-individual inter-sessional reliability for 30min after AtDCS-subjects are likely to maintain their response patterns to tDCS between sessions, with implications for experimental and therapeutic applications of tDCS. Copyright © 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.
- "Several studies have shown that tDCS can improve motor performance and motor learning in healthy subjects, both during (Galea et al., 2011) and after stimulation (Boggio et al., 2006 ). In addition, tDCS holds promise as a therapeutic tool in neurologic diseases such as stroke (Hummel and Cohen, 2006; Zimerman et al., 2012) or epilepsy (Fregni et al., 2006); psychiatric diseases such as depression (Boggio et al., 2008) or drug addiction (Boggio et al., 2010); and in chronic pain (Lefaucheur et al., 2008). However, a source of increasing concern has been that despite initially promising results, a number of studies attempting to replicate findings of prior tDCS studies have not found the same effects (Meesen et al., 2014; O'Connell et al., 2014; Polanowska et al., 2013; Wrigley et al., 2013). "