Successful deep brain stimulation of the nucleus accumbens in severe alcohol dependence is associated with changed performance monitoring

Ethical implications of research on craving

Cravings, intense desires to experience the effects of a drug, are widely regarded as significant impediments to overcoming addiction, although their role in relapse may be overstated. Scientists and clinicians wish to better understand the neurobiological and cognitive basis of craving so that they may develop psychotherapeutic, pharmacological and other medical methods to reduce craving and thereby drug use. The conduct of such research raises significant ethical issues. When recruiting individuals and conducting this research, scientists need to ensure that substance dependent participants have the capacity to provide free and uncoerced consent. This is especially the case in studies in which dependent participants are given their drug of addiction or provided with other inducements to participate (e.g. financial incentives) that may undermine their ability to fully consider the risks of participation. Treatments for addiction that seek to reduce cravings may also carry risks. This includes psychotherapeutic approaches, as well as pharmacological and medical treatments. Clinicians need to consider the risks and benefits of treatment and carefully communicate these to patients. The desire to reduce urges to use drugs should not be employed to justify potentially harmful and ineffective treatments. The safety and effectiveness of emerging treatments should be assessed by well conducted randomized controlled clinical trials.

Involvement of human internal globus pallidus in the early modulation of cortical error-related activity

The detection and assessment of errors are a prerequisite to adapt behavior and improve future performance. Error monitoring is afforded by the interplay between cortical and subcortical neural systems. Ample evidence has pointed to a specific cortical error-related evoked potential, the error-related negativity (ERN), during the detection and evaluation of response errors. Recent models of reinforcement learning implicate the basal ganglia (BG) in early error detection following the learning of stimulus-response associations and in the modulation of the cortical ERN. To investigate the influence of the human BG motor output activity on the cortical ERN during response errors, we recorded local field potentials from the sensorimotor area of the internal globus pallidus and scalp electroencephalogram representing activity from the posterior medial frontal cortex in patients with idiopathic dystonia (hands not affected) during a flanker task. In error trials, a specific pallidal error-related potential arose 60 ms prior to the cortical ERN. The error-related changes in pallidal activity-characterized by theta oscillations-were predictive of the cortical error-related activity as assessed by Granger causality analysis. Our findings show an early modulation of error-related activity in the human pallidum, suggesting that pallidal output influences the cortex at an early stage of error detection.

Wege aus der Abhängigkeit

Hintergrund: Alkohol-assoziierte Reize lösen bei alkoholabhängigen Patienten konditionierte Reaktionen aus, die zu einer erhöhten Motivation der Alkoholeinnahme führen können. Klassische Konditionierungsprozesse scheinen demnach sowohl zur Aufrechterhaltung der Abhängigkeit als auch zum Rückfallgeschehen nach Entzug beizutragen. Bildgebende Studien weisen darauf hin, dass das dopaminerge Neurotransmittersystem an assoziativen Lernvorgängen beteiligt ist und Veränderungen innerhalb dieses Systems bei entgifteten alkoholabhängigen Patienten zum Rückfall beitragen könnten. Die genauen Mechanismen in diesem Zusammenhang sind bisher jedoch ungeklärt. Zielsetzung: Ziel dieser Arbeit ist die Darstellung von motivationalen Veränderungen und deren (neuroadaptiven) Grundlagen bei Alkoholabhängigkeit. Ein genaueres Verständnis davon, welche neuronalen und motivationalen Prozesse im Rahmen des Rückfallgeschehens eine Rolle spielen, könnte sowohl pharmakologische als auch therapeutische Implikationen für die Behandlung der Alkoholabhängigkeit liefern. Methodik: Diese Arbeit umfasst eine Literaturanalyse über neuroadaptive Veränderungen bei Alkoholabhängigkeit mit besonderem Fokus auf Lernprozesse und deren Rolle beim Rückfallgeschehen. Die Literaturrecherche basiert auf Recherchen der Forschergruppe 1617 der Deutschen Forschungsgesellschaft (DFG; Learning and Habitization in Alcohol Dependence, LeAD). Schlussfolgerung: Bisher existieren keine Untersuchungen, in denen neuroadaptive Veränderungen der Alkoholabhängigkeit mit spezifischen Lerndefiziten in Zusammenhang gebracht werden. Die DFG Forschergruppe LeAD untersucht neuronale Korrelate von lernbezogenen Rückfallprädiktoren. Ein Ziel dieser Untersuchung ist es herauszufinden, warum alkoholabhängige Patienten nach ihrer Entgiftung oft nicht lernen, Alkohol durch alternative belohnende Reize und Situation zu ersetzen und welche neuronalen Grundlagen diesem Defizit zu Grunde liegen.

Deep brain stimulation of the nucleus accumbens for the treatment of addiction

Despite novel medications and other therapeutic strategies, addiction to psychotropic substances remains one of the most serious public health problems worldwide. In this review, beginning with an introduction of deep brain stimulation (DBS), we highlight the importance of the nucleus accumbens (NAc) in the context of the reward circuitry and addictive behavior. We will provide a short historic overview of other neurosurgical approaches to treat addiction and describe the experimental and preclinical data on DBS in addiction. Finally, we call attention to key ethical issues related to using DBS to treat addiction that are important for future research and the design of clinical trials.

Brain stimulation methods to treat tobacco addiction

BACKGROUND

Tobacco smoking is the leading cause of preventable deaths worldwide, but many smokers are simply unable to quit. Psychosocial and pharmaceutical treatments have shown modest results on smoking cessation rates, but there is an urgent need to develop treatments with greater efficacy. Brain stimulation methods are gaining increasing interest as possible addiction therapeutics.

OBJECTIVES

The purpose of this paper is to review the studies that have evaluated brain stimulation techniques on tobacco addiction, and discuss future directions for research in this novel area of addiction interventions.

METHODS

Electronic and manual literature searches identified fifteen studies that administered repetitive transcranial magnetic stimulation (rTMS), cranial electrostimulation (CES), transcranial direct current stimulation (tDCS) or deep brain stimulation (DBS).

RESULTS

rTMS was found to be the most well studied method with respect to tobacco addiction. Results indicate that rTMS and tDCS targeted to the dorsolateral prefrontal cortex (DLPFC) were the most efficacious in reducing tobacco cravings, an effect that may be mediated through the brain reward system involved in tobacco addiction. While rTMS was shown to reduce consumption of cigarettes, as yet no brain stimulation technique has been shown to significantly increase abstinence rates. It is possible that the therapeutic effects of rTMS and tDCS may be improved by optimization of stimulation parameters and increasing the duration of treatment.

CONCLUSION

Although further studies are needed to confirm the ability of brain stimulation methods to treat tobacco addiction, this review indicates that rTMS and tDCS both represent potentially novel treatment modalities.