Effects of Non-invasive Neuromodulation on Executive and Other Cognitive Functions in Addictive Disorders: A Systematic Review

Abstract

Background: In order to improve the current treatment of addictive disorders non-invasive neuromodulation over the dorsolateral prefrontal cortex (DLPFC) has gained attention. The DLPFC is crucially involved in executive functioning, functions which are related to the course of addictive disorders. Non-invasive stimulation of the DLPFC may lead to changes in executive functioning. Currently an overview of effects of neuromodulation on these functions is lacking. Therefore, this systematic review addresses the effects of non-invasive neuromodulation on executive functioning in addictive disorders.Methods: The current review is conducted and reported in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses for Protocols 2015 (PRISMA-P 2015) guidelines and has been registered in PROSPERO International Prospective Register of Systematic Reviews (https://www.crd.york.ac.uk/prospero/, registration number: CRD42018084157). Original articles were searched using the Ovid MEDLINE, Embase and PsycINFO database.Results: The systematic search resulted in 1,228 unique studies, of which sixteen were included in the current review. Some of these studies do not address the classic definition of executive functions, but another cognitive function. However, they were included in this review since the field is small and still under development and we aim to give an inclusive overview in its broadest sense. The following executive and other cognitive functioning domains were assessed: attention, cognitive flexibility, response inhibition, memory and learning, problem solving, social cognition, risk taking, cognitive bias modification and overall executive functioning. The executive function domain most positively affected was social cognition followed by memory & learning, response inhibition, cognitive flexibility and attention.Conclusions: The studies addressed in the current review used a large variability of stimulation protocols and study designs which complicates comparability of the results. Nevertheless, the results of these studies are promising in light of improvement of current treatment. Therefore, we recommend future studies that compare the effect of different types of stimulation, stimulation sides and number of stimulation sessions in larger clinical trials. This will significantly increase the comparability of the studies and thereby accelerate and clarify the conclusion on whether non-invasive neuromodulation is an effective add-on treatment for substance dependence.

Baclofen-induced Changes in the Resting Brain Modulate Smoking Cue Reactivity: A Double-blind Placebo-controlled Functional Magnetic Resonance Imaging Study in Cigarette Smokers

“…Our finding that baclofen increased dlPFC activation at rest replicates our previous findings [25] and is consistent with literature implicating the dlPFC in recovery from substance use disorders [24,[60][61][62]. The prevailing theory uniting these studies postulates that increased resting activity in the dlPFC can improve individuals' ability to mitigate conditioned responses that lead to relapse.…”

Transcranial electrical and magnetic stimulation (tES and TMS) for addiction medicine: A consensus paper on the present state of the science and the road ahead

“…In a previous meta-analysis, no laterality effect could be found for either right or left DLPFC stimulation, although there was a trend favoring right-sided DLPFC rTMS (Enokibara et al, 2016;Jansen et al, 2013). Recent reviews on the cognitive effects of tES/rTMS in addiction indicate positive effects of both right-sided and left-sided DLPFC stimulation (Naish et al, 2018;Schluter et al, 2018). Both left-and rightsided stimulation have been shown to enable positive effects on cognition and on craving in addictive disorders, these effects may be due to non-focal effects of rTMS.…”

“…Cognitive deficits associated with decreased prefrontal functioning have been related to SUDs (Kozak et al, 2017) and increased risk of relapse (Dominguez-Salas et al, 2016). Given that neuromodulation can improve cognitive control/functioning, it may (in part) diminish the risk for relapse by strengthening cognitive control (Jansen et al, 2013;Schluter et al, 2018).…”

“…tES/TMS may normalize some of these endophenotypic markers, for instance by enhancing cognitive control through DLPFC stimulation. Neuromodulation like tDCS and rTMS have been shown to reduce craving in substance related disorders (Jansen et al, 2013), and changes in cognitive functioning, mostly indicating improvement of cognitive functioning in addictive disorders following tES/TMS (Schluter et al, 2018). Currently, a very limited number of tES/TMS pilot studies in gambling disorder are present.…”

“…TMS can be used for stimulation or neurophysiological assessment. For stimulation, specifications must also be based on a predefined hypothesis, with clear definition of location; coil shape (H-coil, figure-8 coil) (Coles et al, 2018); frequency (high vs low-frequency stimulation and/or patterned stimulation, if present); number of pulses (and train of pulses in case of high-frequency); duration of the stimulation session; intensity (if defined as a percentage of the motor threshold or a percentage of the output of the machine); and number of sessions (Schluter et al, 2018). It should be clearly defined how the target location was found and whether or not neuronavigation was used.…”