Transcranial magnetic stimulation of dorsolateral prefrontal cortex reduces cocaine use: A pilot study

High frequency deep transcranial magnetic stimulation acutely increases β-endorphins in obese humans

PURPOSE

In obesity, metabolic and voluntary factors regulate appetite, and a dysregulation of the reward pathway was demonstrated in all addiction disorders. Deep transcranial magnetic stimulation (dTMS) is already used to modulate cerebral dopamine activation in neuro-psychiatric diseases. We presently assess the acute effect of high frequency (HF) and low frequency (LF) dTMS on the modulation of the main neuropeptides and neurotransmitters involved in the reward pathway in obese subjects.

METHODS

This study was designed as a double-blind, sham-controlled, randomized clinical trial. Thirty-three obese patients (9 males, 24 females, age 48.1 ± 10.6, BMI 36.4 ± 4.7) were enrolled in the study. All patients were studied during a single dTMS session and blood aliquots were drawn before and after a single dTMS session. Metabolic and neuro-endocrine parameters were evaluated before and after: (1) 18 Hz dTMS (HF, 13 patients); (2) 1 Hz dTMS (LF, 10 patients); (3) Sham treatment (Sham, 10 patients).

RESULTS

No statistically significant variations in metabolic parameters, systolic and diastolic blood pressure, and heart rate were shown acutely. HF showed a significant increase of β-endorphin compared to other groups (p = 0.048); a significant increase of ghrelin in LF (p = 0.041) was also demonstrated.

CONCLUSIONS

A single session of HF dTMS treatment determines in obese subjects an acute increase of β-endorphin level, indicating an activation of the reward pathway. The present findings constitute proof of principle for a potential application of this methodology in obesity treatment.

Repetitive transcranial magnetic stimulation: Re-wiring the alcoholic human brain

Alcohol use disorders (AUDs) are one of the leading causes of mortality and morbidity worldwide. In spite of significant advances in understanding the neural underpinnings of AUDs, therapeutic options remain limited. Recent studies have highlighted the potential of repetitive transcranial magnetic stimulation (rTMS) as an innovative, safe, and cost-effective treatment for AUDs. Here, we summarize the fundamental principles of rTMS and its putative mechanisms of action via neurocircuitries related to alcohol addiction. We will also discuss advantages and limitations of rTMS, and argue that Hebbian plasticity and connectivity changes, as well as state-dependency, play a role in shaping some of the long-term effects of rTMS. Visual imaging studies will be linked to recent clinical pilot studies describing the effect of rTMS on alcohol craving and intake, pinpointing new advances, and highlighting conceptual gaps to be filled by future controlled studies.

Addictive behaviour in experimental animals: prospects for translation

Since the introduction of intravenous drug self-administration methodology over 50 years ago, experimental investigation of addictive behaviour has delivered an enormous body of data on the neural, psychological and molecular mechanisms of drug reward and reinforcement and the neuroadaptations to chronic use. Whether or not these behavioural and molecular studies are viewed as modelling the underpinnings of addiction in humans, the discussion presented here highlights two areas-the impact of drug-associated conditioned stimuli-or drug cues-on drug seeking and relapse, and compulsive cocaine seeking. The degree to which these findings translate to the clinical state of addiction is considered in terms of the underlying neural circuitry and also the ways in which this understanding has helped develop new treatments for addiction. The psychological and neural mechanisms underlying drug memory reconsolidation and extinction established in animal experiments show particular promise in delivering new treatments for relapse prevention to the clinic.This article is part of a discussion meeting issue 'Of mice and mental health: facilitating dialogue between basic and clinical neuroscientists'.

rTMS Reduces Psychopathological Burden and Cocaine Consumption in Treatment-Seeking Subjects With Cocaine Use Disorder: An Open Label, Feasibility Study

Introduction: Cocaine use disorder (CUD) currently represents a notable public health concern, linked with significant disability, high chances of chronicity, and lack of effective pharmacological or psychological treatments. Repetitive transcranial magnetic stimulation (rTMS) is supposed to be a potential therapeutic option for addictive disorders. Aim of this study was to evaluate the feasibility of rTMS on (1) cocaine craving and consumption and (2) other comorbid psychiatric symptoms. Methods: Twenty treatment seeking CUD subjects underwent 2 weeks of intensive rTMS treatment (15Hz; 5 days/week, twice a day for a total of 20 stimulation sessions) of the left dorsolateral prefrontal cortex, followed by 2 weeks of maintenance treatment (15Hz, 1 day/week, twice a day). Sixteen patients completed the study. Patients were evaluated at baseline (T0), after 2 weeks of treatment (T1), and at the end of the study (T2; 4 weeks), with the following scales: Cocaine Selective Severity Assessment (CSSA), Zung Self-Rating Anxiety Scale, Beck Depression Inventory (BDI), Symptom Checklist-90 (SCL-90), and the Insomnia Severity Index. Results: After four weeks of rTMS treatment, 9 out of 16 subjects (56.25%) had a negative urinalysis test, with a significant conversion rate with respect to baseline (Z = -3.00; p = 0.003). Craving scores significantly improved only at T2 (p = 0.020). The overall psychopathological burden, as measured by the SCL-90 Global Severity Index (GSI), significantly decreased during the study period (Z = -2.689; p = 0.007), with a relevant improvement with regards to depressive symptoms, anhedonia, and anxiety. Subjects exhibiting lower baseline scores on the SCL-90 were more likely to be in the positive outcome group at the end of the study (Z = -3.334; p = 0.001). Discussion: Findings from this study are consistent with previous contributions on rTMS use in subjects with cocaine use disorder. We evidenced a specific action on some psychopathological areas and a consequent indirect effect in terms of relapse prevention and craving reduction. A double-blind, sham-controlled, neuro-navigated rTMS study design is needed, in order to confirm the potential benefits of this technique, opening new scenarios in substance use disorders treatment.

A Roadmap for Integrating Neuroscience Into Addiction Treatment: A Consensus of the Neuroscience Interest Group of the International Society of Addiction Medicine

Although there is general consensus that altered brain structure and function underpins addictive disorders, clinicians working in addiction treatment rarely incorporate neuroscience-informed approaches into their practice. We recently launched the Neuroscience Interest Group within the International Society of Addiction Medicine (ISAM-NIG) to promote initiatives to bridge this gap. This article summarizes the ISAM-NIG key priorities and strategies to achieve implementation of addiction neuroscience knowledge and tools for the assessment and treatment of substance use disorders. We cover two assessment areas: cognitive assessment and neuroimaging, and two interventional areas: cognitive training/remediation and neuromodulation, where we identify key challenges and proposed solutions. We reason that incorporating cognitive assessment into clinical settings requires the identification of constructs that predict meaningful clinical outcomes. Other requirements are the development of measures that are easily-administered, reliable, and ecologically-valid. Translation of neuroimaging techniques requires the development of diagnostic and prognostic biomarkers and testing the cost-effectiveness of these biomarkers in individualized prediction algorithms for relapse prevention and treatment selection. Integration of cognitive assessments with neuroimaging can provide multilevel targets including neural, cognitive, and behavioral outcomes for neuroscience-informed interventions. Application of neuroscience-informed interventions including cognitive training/remediation and neuromodulation requires clear pathways to design treatments based on multilevel targets, additional evidence from randomized trials and subsequent clinical implementation, including evaluation of cost-effectiveness. We propose to address these challenges by promoting international collaboration between researchers and clinicians, developing harmonized protocols and data management systems, and prioritizing multi-site research that focuses on improving clinical outcomes.

Behavioral and neural mechanisms underlying habitual and compulsive drug seeking

Addiction is characterized by compulsive drug use despite negative consequences. Here we review studies that indicate that compulsive drug use, and in particular punishment resistance in animal models of addiction, is related to impaired cortical control over habitual behavior. In humans and animals, instrumental behavior is supported by goal-directed and habitual systems that rely on distinct corticostriatal networks. Chronic exposure to addictive drugs or stress has been shown to bias instrumental response strategies toward habit learning, and impair prefrontal cortical (PFC) control over responding. Moreover, recent work has implicated prelimbic PFC hypofunction in the punishment resistance that has been observed in a subset of animals with an extended history of cocaine self-administration. This may be related to a broader role for prelimbic PFC in mediating adaptive responding and behavioral flexibility, including exerting goal-directed control over behavior. We hypothesize that impaired cortical control and reduced flexibility between habitual and goal-directed systems may be critically involved in the development of maladaptive, compulsive drug use.

Transcranial direct current stimulation to prevent and treat surgery-induced opioid dependence: a systematic review

Opioid misuse leading to dependence is a major health issue. Recent studies explored valid alternatives to treat pain in postsurgical settings. This systematic review aims to discuss the role of transcranial direct current stimulation (tDCS) in preventing and treating postoperative pain and opioid dependence. PubMed and Embase databases were screened, considering studies testing tDCS effects on pain and opioid consumption in surgical settings and opioid addiction. Eight studies met our inclusion criteria. Results showed a reduction of postoperative pain, opioid consumption and cue-induced craving following cortical stimulation. Despite the limited number of studies, this review shows preliminary encouraging evidence regarding the analgesic role of tDCS. However, future studies are needed to further investigate the application of tDCS in postsurgical settings.

Food addiction: a valid concept?

Can food be addictive? What does it mean to be a food addict? Do common underlying neurobiological mechanisms contribute to drug and food addiction? These vexing questions have been the subject of considerable interest and debate in recent years, driven in large part by the major health concerns associated with dramatically increasing body weights and rates of obesity in the United States, Europe, and other regions with developed economies. No clear consensus has yet emerged on the validity of the concept of food addiction and whether some individuals who struggle to control their food intake can be considered food addicts. Some, including Fletcher, have argued that the concept of food addiction is unsupported, as many of the defining features of drug addiction are not seen in the context of feeding behaviors. Others, Kenny included, have argued that food and drug addiction share similar features that may reflect common underlying neural mechanisms. Here, Fletcher and Kenny argue the merits of these opposing positions on the concept of food addiction.

Gender-related differences in cue-elicited cravings in Internet gaming disorder: The effects of deprivation

BACKGROUND

Online gaming has become a popular leisure activity, in which males more frequently develop Internet gaming disorder (IGD) compared to females. However, gender-related neurocognitive differences have largely not been systematically investigated in IGD.

METHODS

Cue-elicited-craving tasks were performed before game playing and immediately after deprivation operationalized as a forced break from gaming when the Internet was disconnected. Ninety-nine subjects with IGD (27 males and 22 females) or recreational game use (RGU; 27 males and 23 females) provided functional MRI and subjective data. Analyses investigating effects of group (IGD and RGU) × gender (male and female) at different times (pre-gaming, post-gaming, and post-pre) on cue-elicited craving and brain responses were performed. Correlations between brain responses and subjective measures were calculated.

RESULTS

In pre-, post-, and post-pre tests, significant gender-by-group interactions (p < .001, cluster size > 15 voxels) were observed in the left dorsolateral prefrontal cortex (DLPFC). Further analyses of the DLPFC cluster showed that in post-pre comparisons, results were related to less engagement of the DLPFC in IGD, especially in females. In addition, at post-test, significant interactions were observed in the caudate, as females with IGD showed greater activation as compared to those with RGU.

DISCUSSION

The results raise the possibility that women with RGU may show better executive control than men when facing gaming cues, which may provide resiliency against developing IGD; however, once they develop IGD, their gaming may impair their executive control and enhance their cravings for gaming, which may make it more difficult to quit gaming.

What, If Anything, Is Rodent Prefrontal Cortex?

Prefrontal cortex (PFC) means different things to different people. In recent years, there has been a major increase in publications on the PFC, especially using mice. However, inconsistencies in the nomenclature and anatomical boundaries of PFC areas has made it difficult for researchers to compare data and interpret findings across species. We conducted a meta-analysis of publications on the PFC of humans and rodents and found dramatic differences in the focus of research on these species. In addition, we compared anatomical terms and criteria across several common rodent brain atlases and found inconsistencies among, and even within, leading atlases. To assess the impact of these issues on the research community, we conducted a survey of established PFC researchers on their use of anatomical terms and found little consensus. We report on the results of the survey and propose an alternative scheme for interpreting data from rodent studies, based on structural analysis of the corpus callosum and nomenclature used in research on the anterior cingulate cortex (ACC) of primates.

Cue reactivity and opioid blockade in amphetamine dependence: A randomized, controlled fMRI study

BACKGROUND

The opioid antagonist, naltrexone, has been shown to reduce the risk of relapse in amphetamine dependence, but the mechanisms behind this effect are not well understood. We aimed to investigate if naltrexone attenuates cue reactivity and craving in amphetamine dependence.

METHODS

Forty men with severe, intravenous amphetamine dependence were randomized to one dose of naltrexone (50 mg) or placebo. In a BOLD fMRI cue reactivity paradigm, they were exposed to drug-related and neutral films and gave subjective ratings of craving after each film. Twenty-nine patients left data of sufficient quality to be included in the final analysis.

RESULTS

The drug-related films elicited strong subjective craving and BOLD activations of the striatum, cingulate cortex, and occipito-temporal visual attention networks. Longer history of amphetamine use was associated with greater activations of the prefrontal cortex. Naltrexone as compared to placebo had no significant effects on brain activations or subjective ratings.

CONCLUSION

Patients with severe stimulant use disorder exhibit strong neural cue reactivity, the patterns of which are modulated by duration of drug use. In this sample, we found no evidence for any effects of naltrexone on cue reactivity.

Neuromodulation for substance addiction in human subjects: A review

Substance abuse is one of the most prevalent and costly health problems in the world today. Standard medical therapy is often not curative, and relapse is common. Research over the past several decades on the neural underpinnings of addiction has implicated a network of structures within the brain shown to be altered in patients with substance abuse. The field of neuromodulation aims to utilize this knowledge to treat dysfunctional circuits by targeting and modulating specific brain circuits. While invasive neuromodulation such as DBS and VNS have proven to be effective in treating movement disorders, OCD and epilepsy, there is increasing interest and data with regards to its potential application for the treatment of severe, intractable addiction. Several neuromodulatory techniques and brain targets are currently under investigation in patients with various substance abuse disorders. This review aims to summarize the current state of evidence for neurosurgical neuromodulation as a therapy for substance abuse and addiction, and to provide additional expert opinions as to the obstacles and future directions of this endeavor.

Synaptic and intrinsic plasticity in the ventral tegmental area after chronic cocaine

Cocaine exposure induces persistent changes in synaptic transmission and intrinsic properties of ventral tegmental area (VTA) dopamine neurons. Despite significant progress in understanding cocaine-induced plasticity, an effective treatment of cocaine addiction is lacking. Chronic cocaine potentiates excitatory and alters inhibitory transmission to dopamine neurons, induces dopamine neuron hyperexcitability, and reduces dopamine release in projection areas. Understanding how intrinsic and synaptic plasticity interact to control dopamine neuron firing and dopamine release could prove useful in the development of new therapeutics. In this review, we examine recent literature discussing cocaine-induced plasticity in the VTA and highlight potential therapeutic interventions.

Prefrontal Cortex Represents Long-Term Memory of Object Values for Months

As a central hub for cognitive control, prefrontal cortex (PFC) is thought to utilize memories. However, unlike working or short-term memory, the neuronal representation of long-term memory in PFC has not been systematically investigated. Using single-unit recordings in macaques, we show that PFC neurons rapidly update and maintain responses to objects based on short-term reward history. Interestingly, after repeated object-reward association, PFC neurons continue to show value-biased responses to objects even in the absence of reward. This value-biased response is retained for several months after training and is resistant to extinction and to interference from new object-reward learning for many complex objects (>90). Accordingly, the monkeys remember the values of the learned objects for several months in separate testing. These findings reveal that in addition to flexible short-term and low-capacity memories, primate PFC represents stable long-term and high-capacity memories, which could prioritize valuable objects far into the future.

Low-frequency repetitive transcranial magnetic stimulation inhibits the development of methamphetamine-induced conditioned place preference

The abuse of amphetamine-type stimulants (ATS) has become a global public health issue in recent years, these new-type drugs can cause addiction and serious cognitive impairment. However, there are no effective methods for the prevention and treatment of ATS addiction at present. Repetitive transcranial magnetic stimulation (rTMS) is a painless and non-invasive new therapeutic approach that has been used for the treatment of depression and other neuropsychiatric disorders, but whether it can be used to treat drug addiction is unclear. In the present study, we investigated the possible effects of rTMS on methamphetamine(METH)-induced conditioned place preference (CPP). High-frequency (10 Hz) and low-frequency stimulation patterns (1 Hz) were applied to test the effect of rTMS on METH-induced CPP. The results showed that low-frequency but not high-frequency rTMS could block METH-CPP, accompanied with a downregulation of gamma-aminobutyric acid type B receptor subunit 1 (GABA_BR1) expression in rat dorsolateral striatum. These results suggested that low-frequency rTMS could effectively inhibit the development of METH addiction and shed light on the rTMS as a potential approach for the prevention of drug addiction.

Modulating Neural Circuits with Transcranial Magnetic Stimulation: Implications for Addiction Treatment Development

Although the last 50 years of clinical and preclinical research have demonstrated that addiction is a brain disease, we still have no neural circuit-based treatments for substance dependence or cue reactivity at large. Now, for the first time, it appears that a noninvasive brain stimulation technique known as transcranial magnetic stimulation (TMS), which is Food and Drug Administration approved to treat depression, may be the first tool available to fill this critical void in addiction treatment development. The goals of this review are to 1) introduce TMS as a tool to induce causal change in behavior, cortical excitability, and frontal-striatal activity; 2) describe repetitive TMS (rTMS) as an interventional tool; 3) provide an overview of the studies that have evaluated rTMS as a therapeutic tool for alcohol and drug use disorders; and 4) outline a conceptual framework for target selection when designing future rTMS clinical trials in substance use disorders. The manuscript concludes with some suggestions for methodological innovation, specifically with regard to combining rTMS with pharmacotherapy as well as cognitive behavioral training paradigms. We have attempted to create a comprehensive manuscript that provides the reader with a basic set of knowledge and an introduction to the primary experimental questions that will likely drive the field of TMS treatment development forward for the next several years.

Impact of Sleep and Circadian Rhythms on Addiction Vulnerability in Adolescents

Sleep homeostasis and circadian function are important maintaining factors for optimal health and well-being. Conversely, sleep and circadian disruptions are implicated in a variety of adverse health outcomes, including substance use disorders. These risks are particularly salient during adolescence. Adolescents require 8 to 10 hours of sleep per night, although few consistently achieve these durations. A mismatch between developmental changes and social/environmental demands contributes to inadequate sleep. Homeostatic sleep drive takes longer to build, circadian rhythms naturally become delayed, and sensitivity to the phase-shifting effects of light increases, all of which lead to an evening preference (i.e., chronotype) during adolescence. In addition, school start times are often earlier in adolescence and the use of electronic devices at night increases, leading to disrupted sleep and circadian misalignment (i.e., social jet lag). Social factors (e.g., peer influence) and school demands further impact sleep and circadian rhythms. To cope with sleepiness, many teens regularly consume highly caffeinated energy drinks and other stimulants, creating further disruptions in sleep. Chronic sleep loss and circadian misalignment enhance developmental tendencies toward increased reward sensitivity and impulsivity, increasing the likelihood of engaging in risky behaviors and exacerbating the vulnerability to substance use and substance use disorders. We review the neurobiology of brain reward systems and the impact of sleep and circadian rhythms changes on addiction vulnerability in adolescence and suggest areas that warrant additional research.

Transcranial magnetic stimulation for the treatment of cocaine addiction: evidence to date

There is a common consensus in considering substance-use disorders (SUDs) a devastating chronic illness with social and psychological impact. Despite significant progress in understanding the neurobiology of SUDs, therapeutic advances have proceeded at a slower pace, in particular for cocaine-use disorder (CUD). Transcranial magnetic stimulation (TMS) is gaining support as a safe and cost-effective tool in the treatment of SUDs. In this review, we consider human studies that have investigated the efficacy of TMS in achieving therapeutic benefits in treating CUD. All studies conducted to date that have evaluated the therapeutic effect of TMS in CUD are included. We focus on the protocol of stimulation applied, emphasizing the neurophysiological effects of coils employed related to outcomes. Moreover, we examine the subjective and objective measurements used to assess the therapeutic effects along the timeline considered. The revision of scientific literatures underscores the therapeutic potential of TMS in treating CUD. However, the variability in stimulation protocols applied and the lack of methodological control do not allow us to draw firm conclusions, and further studies are warranted to examine the interaction between TMS patterns of stimulation relative to clinical outcomes in depth.

Transdiagnostic Effects of Ventromedial Prefrontal Cortex Transcranial Magnetic Stimulation on Cue Reactivity

BACKGROUND

Elevated frontal and striatal reactivity to drug cues is a transdiagnostic hallmark of substance use disorders. The goal of these experiments was to determine if it is possible to decrease frontal and striatal reactivity to drug cues in both cocaine users and heavy alcohol users through continuous theta burst stimulation (cTBS) to the left ventromedial prefrontal cortex (VMPFC).

METHODS

Two single-blinded, within-subject, active sham-controlled experiments were performed wherein neural reactivity to drug/alcohol cues versus neutral cues was evaluated immediately before and after receiving real or sham cTBS (110% resting motor threshold, 3600 pulses, Fp1 location; N = 49: 25 cocaine users [experiment 1], 24 alcohol users [experiment 2]; 196 total functional magnetic resonance imaging scans). Generalized psychophysiological interaction and three-way repeated-measures analysis of variance were used to evaluate cTBS-induced changes in drug cue-associated functional connectivity between the left VMPFC and eight regions of interest: ventral striatum, left and right caudate, left and right putamen, left and right insula, and anterior cingulate cortex.

RESULTS

In both experiments, there was a significant interaction between treatment (real/sham) and time (pre/post). In both experiments, cue-related functional connectivity was significantly attenuated following real cTBS versus sham cTBS. There was no significant interaction with region of interest for either experiment.

CONCLUSIONS

This is the first sham-controlled investigation to demonstrate, in two populations, that VMPFC cTBS can attenuate neural reactivity to drug and alcohol cues in frontostriatal circuits. These results provide an empirical foundation for future clinical trials that may evaluate the efficacy, durability, and clinical implications of VMPFC cTBS to treat addictions.

Double-blind evaluation of homeopathy on cocaine craving: a randomized controlled pilot study

BACKGROUND

Brazil is among the nations with the greatest rates of annual cocaine usage. Pharmacological treatment of cocaine addiction is still limited, opening space for nonconventional interventions. Homeopathic Q-potencies of opium and Erythroxylum coca have been tested in the integrative treatment of cocaine craving among homeless addicts, but this setting had not proven feasible, due to insufficient recruitment.

OBJECTIVE

This study investigates the effectiveness and tolerability of homeopathic Q-potencies of opium and E. coca in the integrative treatment of cocaine craving in a community-based psychosocial rehabilitation setting.

DESIGN, SETTING, PARTICIPANTS, AND INTERVENTIONS

A randomized, double-blind, placebo-controlled, parallel-group, eight-week pilot trial was performed at the Psychosocial Attention Center for Alcohol and Other Drugs (CAPS-AD), Sao Carlos/SP, Brazil. Eligible subjects included CAPS-AD patients between 18 and 65 years of age, with an International Classification of Diseases-10 diagnosis of cocaine dependence (F14.2). The patients were randomly assigned to two treatment groups: psychosocial rehabilitation plus homeopathic Q-potencies of opium and E. coca (homeopathy group), and psychosocial rehabilitation plus indistinguishable placebo (placebo group).

MAIN OUTCOME MEASURES

The main outcome measure was the percentage of cocaine-using days. Secondary measures were the Minnesota Cocaine Craving Scale and 12-Item Short-Form Health Survey scores. Adverse events were reported in both groups.

RESULTS

The study population comprised 54 patients who attended at least one post-baseline assessment, out of the 104 subjects initially enrolled. The mean percentage of cocaine-using days in the homeopathy group was 18.1% (standard deviation (SD): 22.3%), compared to 29.8% (SD: 30.6%) in the placebo group (P < 0.01). Analysis of the Minnesota Cocaine Craving Scale scores showed no between-group differences in the intensity of cravings, but results significantly favored homeopathy over placebo in the proportion of weeks without craving episodes and the patients' appraisal of treatment efficacy for reduction of cravings. Analysis of 12-Item Short-Form Health Survey scores found no significant differences. Few adverse events were reported: 0.57 adverse events/patient in the homeopathy group compared to 0.69 adverse events/patient in the placebo group (P = 0.41).

CONCLUSIONS

A psychosocial rehabilitation setting improved recruitment but was not sufficient to decrease dropout frequency among Brazilian cocaine treatment seekers. Psychosocial rehabilitation plus homeopathic Q-potencies of opium and E. coca were more effective than psychosocial rehabilitation alone in reducing cocaine cravings. Due to high dropout rate and risk of bias, further research is required to confirm our findings, with specific focus on strategies to increase patient retention.

TRIAL REGISTRATION

RBR-2xzcwz (http://www.ensaiosclinicos.gov.br).

Effects of repetitive transcranial magnetic stimulation and trans-spinal direct current stimulation associated with treadmill exercise in spinal cord and cortical excitability of healthy subjects: A triple-blind, randomized and sham-controlled study

Repetitive transcranial magnetic stimulation (rTMS) over motor cortex and trans-spinal direct current stimulation (tsDCS) modulate corticospinal circuits in healthy and injured subjects. However, their associated effects with physical exercise is still not defined. This study aimed to investigate the effect of three different settings of rTMS and tsDCS combined with treadmill exercise on spinal cord and cortical excitability of healthy subjects. We performed a triple blind, randomized, sham-controlled crossover study with 12 healthy volunteers who underwent single sessions of rTMS (1Hz, 20Hz and Sham) and tsDCS (anodal, cathodal and Sham) associated with 20 minutes of treadmill walking. Cortical excitability was assessed by motor evoked potential (MEP) and spinal cord excitability by the Hoffmann reflex (Hr), nociceptive flexion reflex (NFR) and homosynaptic depression (HD). All measures were assessed before, immediately, 30 and 60 minutes after the experimental procedures. Our results demonstrated that anodal tsDCS/treadmill exercise reduced MEP's amplitude and NFR's area compared to sham condition, conversely, cathodal tsDCS/treadmill exercise increased NFR's area. High-frequency rTMS increased MEP's amplitude and NFR's area compared to sham condition. Anodal tsDCS/treadmill exercise and 20Hz rTMS/treadmill exercise reduced Hr amplitude up to 30 minutes after stimulation offset and no changes were observed in HD measures. We demonstrated that tsDCS and rTMS combined with treadmill exercise modulated cortical and spinal cord excitability through different mechanisms. tsDCS modulated spinal reflexes in a polarity-dependent way acting at local spinal circuits while rTMS probably promoted changes in the presynaptic inhibition of spinal motoneurons. In addition, the association of two neuromodulatory techniques induced long-lasting changes.

Current and emerging neuromodulation therapies for addiction: insight from pre-clinical studies

Neuromodulation therapies such as deep brain stimulation or transcranial magnetic stimulation have shown promise in reducing symptoms of addiction when applied to the prefontal cortex, nucleus accumbens or subthalamic nucleus. Pre-clinical investigations implicate modulation of the cortico-basal ganglia network in these therapeutic effects, and this mechanistic understanding is necessary to optimize stimulation paradigms. Recently, the principle that neuromodulation can reverse drug-evoked synaptic plasticity and reduce behavioral symptoms of addiction has inspired novel stimulation paradigms that have long-term effects in animal models. Pre-clinical studies have also raised the possibility that tailoring neuromodulation protocols can modulate distinct symptoms of addiction. Combining mechanistic knowledge of circuit dysfunction with emerging technologies for non-invasive neuromodulation holds promise for developing therapies for addiction and related disorders.

A review of brain stimulation methods to treat substance use disorders

BACKGROUND

Substance use disorders (SUDs) are a leading cause of disability worldwide. While several pharmacological and behavioral treatments for SUDs are available, these may not be effective for all patients. Recent studies using non-invasive neuromodulation techniques including Repetitive Transcranial Magnetic Stimulation (rTMS), Transcranial Direct Current Stimulation (tDCS), and Deep Brain Stimulation (DBS) have shown promise for SUD treatment.

OBJECTIVE

Multiple studies were evaluated investigating the therapeutic potential of non-invasive brain stimulation techniques in treatment of SUDs.

METHOD

Through literature searches (eg, PubMed, Google Scholar), 60 studies (2000-2017) were identified examining the effect of rTMS, tDCS, or DBS on cravings and consumption of SUDs, including tobacco, alcohol, cannabis, opioids, and stimulants.

RESULTS

rTMS and tDCS demonstrated decreases in drug craving and consumption, while early studies with DBS suggest similar results. Results are most encouraging when stimulation is targeted to the Dorsolateral Prefrontal Cortex (DLPFC).

CONCLUSIONS

Short-term treatment with rTMS and tDCS may have beneficial effects on drug craving and consumption. Future studies should focus on extending therapeutic benefits by increasing stimulation frequency and duration of treatment.

SCIENTIFIC SIGNIFICANCE

The utility of these methods in SUD treatment and prevention are unclear, and warrants further study using randomized, controlled designs. (Am J Addict 2018;27:71-91).

Temporal-prefrontal cortical network for discrimination of valuable objects in long-term memory

Remembering and discriminating objects based on their previously learned values are essential for goal-directed behaviors. While the cerebral cortex is known to contribute to object recognition, surprisingly little is known about its role in retaining long-term object-value associations. To address this question, we trained macaques to arbitrarily associate small or large rewards with many random fractal objects (>100) and then used fMRI to study the long-term retention of value-based response selectivity across the brain. We found a pronounced long-term value memory in core subregions of temporal and prefrontal cortex where, several months after training, fractals previously associated with high reward ("good" stimuli) elicited elevated fMRI responses compared with those associated with low reward ("bad" stimuli). Similar long-term value-based modulation was also observed in subregions of the striatum, amygdala, and claustrum, but not in the hippocampus. The value-modulated temporal-prefrontal subregions showed strong resting-state functional connectivity to each other. Moreover, for areas outside this core, the magnitude of long-term value responses was predicted by the strength of resting-state functional connectivity to the core subregions. In separate testing, free-viewing gaze behavior indicated that the monkeys retained stable long-term memory of object value. These results suggest an implicit and high-capacity memory mechanism in the temporal-prefrontal circuitry and its associated subcortical regions for long-term retention of object-value memories that can guide value-oriented behavior.

Neurostimulation techniques in the treatment of cocaine dependence: A review of the literature

OBJECTIVE

Cocaine use disorder is a very common condition that represents a substantial public health problem, and no effective pharmacological or psychological therapies have been identified to date. Urgent therapeutic alternatives are therefore needed such as neurostimulation techniques. The purpose of this review is to describe and discuss studies that have evaluated the safety and efficacy of these techniques for the treatment of cocaine dependence.

METHODS

The electronic literature on repetitive transcranial magnetic stimulation, theta-burst stimulation, deep transcranial magnetic stimulation, transcranial direct current stimulation, magnetic seizure therapy, electroconvulsive therapy, cranial electro-stimulation, and deep brain stimulation in the treatment of cocaine addiction were reviewed.

RESULTS

Most of these studies which are few in numbers and with limited sample sizes found that some of these neurostimulation techniques, particularly transcranial magnetic stimulation, and transcranial direct current stimulation are safe and potentially effective in the reduction of craving to cocaine. Although deep brain stimulation showed some good results in one patient, no conclusion can be drawn so far concerning the efficacy and safety of this approach.

CONCLUSION

Given the somewhat promising results of some of the studies, future controlled studies with larger samples, and optimal stimulus parameters should be designed to confirm the short- and long-term safety and efficacy of neurostimulation techniques to treat cocaine addiction.

Transcranial Magnetic Stimulation of Medial Prefrontal and Cingulate Cortices Reduces Cocaine Self-Administration: A Pilot Study

BACKGROUND

Previous studies have shown that repetitive transcranial magnetic stimulation (rTMS) to the dorsolateral prefrontal cortex may serve as a potential treatment for cocaine use disorder (CUD), which remains a public health problem that is refractory to treatment. The goal of this pilot study was to investigate the effect of rTMS on cocaine self-administration in the laboratory. In the self-administration sessions, CUD participants chose between cocaine and an alternative reinforcer (money) in order to directly measure cocaine-seeking behavior. The rTMS was delivered with the H7 coil, which provides stimulation to the medial prefrontal cortex (mPFC) and anterior cingulate cortex (ACC). These brain regions were targeted based on previous imaging studies demonstrating alterations in their activation and connectivity in CUD.

METHODS

Volunteers with CUD were admitted to an inpatient unit for the entire study and assigned to one of three rTMS groups: high frequency (10 Hz), low frequency (1 Hz), and sham. Six participants were included in each group and the rTMS was delivered on weekdays for 3 weeks. The cocaine self-administration sessions were performed at three time points: at baseline (pre-TMS, session 1), after 4 days of rTMS (session 2), and after 13 days of rTMS (session 3). During each self-administration session, the outcome measure was the number of choices for cocaine.

RESULTS

The results showed a significant group by time effect (p = 0.02), where the choices for cocaine decreased between sessions 2 and 3 in the high frequency group. There was no effect of rTMS on cocaine self-administration in the low frequency or sham groups.

CONCLUSION

Taken in the context of the existing literature, these results contribute to the data showing that high frequency rTMS to the prefrontal cortex may serve as a potential treatment for CUD.

Machine Learning Based Classification of Deep Brain Stimulation Outcomes in a Rat Model of Binge Eating Using Ventral Striatal Oscillations

Neuromodulation-based interventions continue to be evaluated across an array of appetitive disorders but broader implementation of these approaches remains limited due to variable treatment outcomes. We hypothesize that individual variation in treatment outcomes may be linked to differences in the networks underlying these disorders. Here, Sprague-Dawley rats received deep brain stimulation separately within each nucleus accumbens (NAc) sub-region (core and shell) using a within-animal crossover design in a rat model of binge eating. Significant reductions in binge size were observed with stimulation of either target but with significant variation in effectiveness across individuals. When features of local field potentials (LFPs) recorded from the NAc were used to classify the pre-defined stimulation outcomes (response or non-response) from each rat using a machine-learning approach (lasso), stimulation outcomes could be classified with greater accuracy than expected by chance (effect sizes: core = 1.13, shell = 1.05). Further, these LFP features could be used to identify the best stimulation target for each animal (core vs. shell) with an effect size = 0.96. These data suggest that individual differences in underlying network activity may relate to the variable outcomes of circuit based interventions, and measures of network activity could have the potential to individually guide the selection of an optimal stimulation target to improve overall treatment response rates.

21st century neurobehavioral theories of decision making in addiction: Review and evaluation

This review critically examines neurobehavioral theoretical developments in decision making in addiction in the 21st century. We specifically compare each theory reviewed to seven benchmarks of theoretical robustness, based on their ability to address: why some commodities are addictive; developmental trends in addiction; addiction-related anhedonia; self-defeating patterns of behavior in addiction; why addiction co-occurs with other unhealthy behaviors; and, finally, means for the repair of addiction. We have included only self-contained theories or hypotheses which have been developed or extended in the 21st century to address decision making in addiction. We thus review seven distinct theories of decision making in addiction: learning theories, incentive-sensitization theory, dopamine imbalance and systems models, opponent process theory, strength models of self-control failure, the competing neurobehavioral decision systems theory, and the triadic systems theory of addiction. Finally, we have directly compared the performance of each of these theories based on the aforementioned benchmarks, and highlighted key points at which several theories have coalesced.

Reduced interhemispheric executive control network coupling in men during early cocaine abstinence: A pilot study

BACKGROUND

Individuals who use cocaine have fewer cognitive resources needed to maintain abstinence. This is evidenced by blunted brain function during cognitive control tasks and reduced communication between brain regions associated with cognitive function. For instance, relapse vulnerability is heightened in individuals with less communication between the right and left frontoparietal executive control network (ECN). Given that recent cocaine use enhances such communication, it is plausible that recency of cocaine use influences interhemispheric ECN communication. However, it is unclear whether ECN communication weakens over the course of early cocaine abstinence, which may then enhance relapse risk.

METHODS

In ten men with cocaine use disorder, we conducted a preliminary assessment of the relationship between the number of days since last cocaine use (1-3days) and interhemispheric ECN coupling using resting state functional magnetic resonance imaging (fMRI).

RESULTS

Reduced interhemispheric ECN coupling was associated with increasing days since last cocaine use; weaker coupling was also associated with lower urine cocaine metabolite concentrations. This association was more prominent in prefrontal than parietal ECN-subregions.

CONCLUSIONS

Preliminary results indicate that resting state interhemispheric ECN coupling weakens within the first few days following last cocaine use. Because of the known link between reduced ECN interhemispheric coupling and relapse vulnerability, these results suggest that relapse risk may increase the longer an individual abstains during an early quit attempt. Treatments focused on reversing this coupling deficit may facilitate abstinence.

Developing Repetitive Transcranial Magnetic Stimulation (rTMS) as a Treatment Tool for Cocaine Use Disorder: a Series of Six Translational Studies

PURPOSE OF THE REVIEW

Cocaine dependence is a chronic and relapsing disorder which is particularly resistant to behavioral or pharmacologic treatment, and likely involves multiple dysfunctional frontal-striatal circuits. Through advances in preclinical research in the last decade, we now have an unprecedented understanding of the neural control of drug-taking behavior. In both rodent models and human clinical neuroimaging studies, it is apparent that medial frontal-striatal limbic circuits regulate drug cue-triggered behavior. While non-human preclinical studies can use invasive stimulation techniques to inhibit drug cue-evoked behavior, in human clinical neuroscience, we are pursuing non-invasive theta burst stimulation (TBS) as a novel therapeutic tool to inhibit drug cue-associated behavior.

RECENT FINDINGS

Our laboratory and others have spent the last 7 years systematically and empirically developing a non-invasive, neural circuit-based intervention for cocaine use disorder. Utilizing a multimodal approach of functional brain imaging and brain stimulation, we have attempted to design and optimize a repetitive transcranial magnetic stimulation treatment protocol for cocaine use disorder. This manuscript will briefly review the data largely from our own lab that motivated our selection of candidate neural circuits, and then summarize the results of six studies, culminating in the first double-blinded, sham-controlled clinical trial of TMS as a treatment adjuvant for treatment-engaged cocaine users (10 sessions, medial prefrontal cortex, 110% resting motor threshold, continuous theta burst stimulation, 3600 pulses/session).

SUMMARY

The intent of this review is to highlight one example of a systematic path for TMS treatment development in patients. This path is not necessarily optimal, exclusive, or appropriate for every neurologic or psychiatric disease. Rather, it is one example of a reasoned, empirically derived pathway which we hope will serve as scaffolding for future investigators seeking to develop TMS treatment protocols.

Either at left or right, both high and low frequency rTMS of dorsolateral prefrontal cortex decreases cue induced craving for methamphetamine

BACKGROUND AND OBJECTIVES

The study is to investigate if left or right dorsolateral prefrontal cortex is important in modulating the craving to drug related cues.

METHODS

The present investigation examined different combinations between left/right and high/low frequency rTMS on cue induced craving to methamphetamine, with active sham rTMS on P3 region on a total of 50 subjects.

RESULTS

The results showed that either at left or right side, both high and low frequency rTMS are effective in decreasing the cue induced craving to methamphetamine.

DISCUSSION AND CONCLUSIONS

In conclusion, bilateral frontal hemispheres are effective in modulating the cue induced craving to methamphetamine with rTMS.

SCIENTIFIC SIGNIFICANCE

TMS targeting prefrontal cortex is effective for craving modulation; however the mechanism is more than potentiation or depression of single brain region. (Am J Addict 2017;26:776-779).

Updated Review on the Clinical Use of Repetitive Transcranial Magnetic Stimulation in Psychiatric Disorders

With the ability to modulate cortical activity, repetitive transcranial magnetic stimulation (rTMS) is becoming increasingly important in clinical applications for psychiatric disorders. Previous studies have demonstrated its promising efficacy in depression and schizophrenia, and emerging evidence has also been found in patients with anxiety disorder, obsessive-compulsive disorder, and substance or food craving. However, the overall literature features some conflicting results, varied quality of studies, and a lack of consensus on optimal rTMS parameters. Besides, the efficacy of rTMS in patients with medication-resistant symptoms has drawn most attention from clinicians. Here we review multi-site studies and double-blind randomized controlled trials (RCTs) in single sites, as well as meta-analyses of RCTs in the last three years, in order to update evidence on efficacy and the optimal protocol of rTMS in psychiatric disorders, especially for medication-resistant symptoms.

A prospective study of the motivational and health dynamics of Internet Gaming Disorder

The American Psychiatric Association has identified Internet Gaming Disorder (IGD) as a potential psychiatric condition and called for research to investigate its etiology, stability, and impacts on health and behavior. The present study recruited 5,777 American adults and applied self-determination theory to examine how motivational factors influence, and are influenced by, IGD and health across a six month period. Following a preregistered analysis plan, results confirmed our hypotheses that IGD criteria are moderately stable and that they and basic psychological need satisfaction have a reciprocal relationship over time. Results also showed need satisfaction promoted health and served as a protective factor against IGD. Contrary to what was hypothesized, results provided no evidence directly linking IGD to health over time. Exploratory analyses suggested that IGD may have indirect effects on health by way of its impact on basic needs. Implications are discussed in terms of existing gaming addiction and motivational frameworks.

Rehabilitating the addicted brain with transcranial magnetic stimulation

Substance use disorders (SUDs) are one of the leading causes of morbidity and mortality worldwide. In spite of considerable advances in understanding the neural underpinnings of SUDs, therapeutic options remain limited. Recent studies have highlighted the potential of transcranial magnetic stimulation (TMS) as an innovative, safe and cost-effective treatment for some SUDs. Repetitive TMS (rTMS) influences neural activity in the short and long term by mechanisms involving neuroplasticity both locally, under the stimulating coil, and at the network level, throughout the brain. The long-term neurophysiological changes induced by rTMS have the potential to affect behaviours relating to drug craving, intake and relapse. Here, we review TMS mechanisms and evidence that rTMS is opening new avenues in addiction treatments.

Anaesthesia, not number of sessions, influences the magnitude and duration of an aHF-rTMS in dogs

BACKGROUND

Currently, the rat has been a useful animal model in brain stimulation research. Nevertheless, extrapolating results from rodent repetitive Transcranial Magnetic Stimulation (rTMS) research to humans contains several hurdles. This suggests the desperate need for a large animal model in translational rTMS research. The dog would be a valid choice, not only due to the fact that humans and dogs share a neurophysiological background, but a similar neuropathological background as well.

HYPOTHESIS

In order to evaluate the feasibility of the canine rTMS animal model, this study aimed to evaluate the neurophysiological response in dogs on a, clinically used, accelerated high frequency (aHF) rTMS protocol. This aHF-rTMS (20 Hz) protocol was performed under anaesthesia or sedation and either 20 sessions or 5 sessions were given to each dog.

METHODS

21 healthy dogs were randomly subjected to one of the four aHF-rTMS protocols (1 sham and 3 active protocols). For each dog, the perfusion indices (PI), of a [99mTc]HMPAO scan at 4 time points, for the left frontal cortex (stimulation target) were calculated for each protocol.

RESULTS

Concerning sham stimulation, the average PI remained at the baseline level. The main result was the presence of a direct transitory increase in rCBF at the stimulation site, both under anaesthesia and sedation. Nevertheless the measured increase in rCBF was higher but shorter duration under sedation. The magnitude of this increase was not influenced by number of sessions. No changes in rCBF were found in remote brain regions.

CONCLUSION

This study shows that, despite the influence of anaesthesia and sedation, comparable and clinically relevant effects on the rCBF can be obtained in dogs. Since less methodological hurdles have to be overcome and comparable results can be obtained, it would be acceptable to put the dog forward as an alternative translational rTMS animal model.

Affective Processing in Non-invasive Brain Stimulation Over Prefrontal Cortex

The prefrontal cortex (PFC) is the most frequently targeted brain region by non-invasive brain stimulation (NBS) studies. Non-invasively stimulating the PFC has been shown to both modulate affective processing and improve the clinical symptoms of several psychiatric disorders, such as depression and schizophrenia. The magnitude of the modulation depends on several factors, including the stimulation frequency, the number of stimulation sessions, and the specific sub-region of the PFC that is stimulated. Although some of the potential underlying mechanisms have been identified, the exact mechanisms that underlie these cognitive and affective changes remain unclear. The present review aims to summarize recent advances in the study of affective processing using NBS over the PFC. We will provide a theoretical framework for better understanding how affective processing changes are induced by NBS, with the goal of providing testable hypotheses for future studies.

Transcranial Direct Current Stimulation in Substance Use Disorders: A Systematic Review of Scientific Literature

INTRODUCTION

New treatment options such as noninvasive brain stimulation have been recently explored in the field of substance use disorders (SUDs), including transcranial direct current stimulation (tDCS).

OBJECTIVES

In light of this, we have performed a review of the scientific literature to assess efficacy and technical and methodological issues resulting from applying tDCS to the field of SUDs.

METHODS

Our analysis highlighted the following selection criteria: clinical studies on tDCS and SUDs (alcohol, caffeine, cannabis, cocaine, heroin, methamphetamine, and nicotine). Study selection, data analysis, and reporting were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Exclusion criteria were as follows: clinical studies about tDCS among behavioral addiction; review and didactic articles; physiopathological studies; and case reports.

RESULTS

Eighteen scientific papers were selected out of 48 articles. Among these, 16 studied the efficacy of tDCS applied to the dorsolateral prefrontal cortex, and 8 suggested the efficacy of tDCS in reducing substance craving.

CONCLUSIONS

In light of these data, it is premature to conclude that tDCS over the dorsolateral prefrontal cortex is a very efficient technique in reducing craving. Small sample size, different stimulation protocols, and study duration were the main limitations. However, the efficacy of tDCS in treating SUDs requires further investigation.

Repetitive transcranial magnetic stimulation (rTMS) administration to heavy cannabis users

BACKGROUND

Cannabis use disorder (CUD) is a common condition with few treatments. Several studies in other substance use disorders have found that applying repetitive transcranial magnetic stimulation (rTMS) to the dorsolateral prefrontal cortex (DLPFC) decreases cue-elicited craving and possibly decreases use. To date, there have been no studies attempting to use rTMS in CUD.

OBJECTIVES

This study was conducted to determine if rTMS could be feasibly delivered to a group of non-treatment seeking CUD participants. Secondarily, the study aimed to estimate the effect of rTMS on craving.

METHODS

In a double-blind, sham-controlled, crossover design, a single session of active or sham rTMS (Left DLPFC, 10 Hz, 110% rMT, 4000 pulses) was delivered during a validated cannabis cue paradigm. Participants crossed over to complete the other condition one week later. The feasibility and tolerability were measured by the rate of retention, and the percentage of participants able to tolerate full dose rTMS, respectively. Craving was measured using the Marijuana Craving Questionnaire (MCQ).

RESULTS

Eighteen non-treatment seeking CUD participants were recruited from the community; 16 (three women) completed the trial (89% retained for the three study visits). All of the treatment completers tolerated rTMS at full dose without adverse effects. There was not a significant reduction in the total MCQ when participants received active rTMS as compared to sham rTMS.

CONCLUSION

rTMS can be safely and feasibly delivered to CUD participants, and treatment is well tolerated. A single session of rTMS applied to the DLPFC may not reduce cue-elicited craving in heavy cannabis users.

Machine Learning of Functional Magnetic Resonance Imaging Network Connectivity Predicts Substance Abuse Treatment Completion

BACKGROUND

Successfully treating illicit drug use has become paramount, yet elusive. Devising specialized treatment interventions could increase positive outcomes, but it is necessary to identify risk factors of poor long-term outcomes to develop specialized, efficacious treatments. We investigated whether functional network connectivity (FNC) measures were predictive of substance abuse treatment completion using machine learning pattern classification of functional magnetic resonance imaging data.

METHODS

Treatment-seeking stimulant- or heroin-dependent incarcerated participants (n = 139; 89 women) volunteered for a 12-week substance abuse treatment program. Participants performed a response inhibition Go/NoGo functional magnetic resonance imaging task prior to onset of the substance abuse treatment. We tested whether FNC related to the anterior cingulate cortex would be predictive of those who would or would not complete a 12-week substance abuse treatment program.

RESULTS

Machine learning pattern classification models using FNC between networks incorporating the anterior cingulate cortex, striatum, and insula predicted which individuals would (sensitivity: 81.31%) or would not (specificity: 78.13%) complete substance abuse treatment. FNC analyses predicted treatment completion above and beyond other clinical assessment measures, including age, sex, IQ, years of substance use, psychopathy, anxiety and depressive symptomatology, and motivation for change.

CONCLUSIONS

Aberrant neural network connections predicted substance abuse treatment outcomes, which could illuminate new targets for developing interventions designed to reduce or eliminate substance use while facilitating long-term outcomes. This work represents the first application of machine-learning models of FNC analyses of functional magnetic resonance imaging data to predict which substance abusers would or would not complete treatment.

Emerging areas of transcranial magnetic stimulation use in psychiatry

Transcranial magnetic stimulation (TMS) is most widely known clinically as a treatment for medication-refractory major depressive disorder, but it holds promise in a number of other areas. In addition to emerging neurologic areas of investigation such as in mild cognitive impairment, dementia, Parkinson's disease and stroke rehab, novel approaches to psychiatric conditions are also being explored. This review provides a critical condensation of the available data assessing the efficacy of TMS in the treatment of other psychiatric conditions, namely bipolar disorder, substance use, post-traumatic stress disorder and other anxiety disorders. Each section details the field's current accumulation of evidence of the respective condition's pathophysiology in the context of a discussion of the relevant therapeutic target(s) of TMS. Each section then reviews both positive and negative studies evaluating TMS in clinical practice. Given the relative tolerability and proven efficacy of TMS in treatment-resistant depression (TRD), further study to determine its therapeutic effect in other psychiatric entities is warranted.

Gene Network Dysregulation in Dorsolateral Prefrontal Cortex Neurons of Humans with Cocaine Use Disorder

Metabolic and functional alterations of neurons in the dorsolateral prefrontal cortex (dlPFC) are thought to contribute to impulsivity, which is a hallmark of addictive behaviors that underlie compulsive drug seeking and taking in humans. To determine if there is a transcriptional signature in dlPFC neurons of humans with cocaine use disorder, we performed total RNA-sequencing on neuronal nuclei isolated from post-mortem dlPFC of cocaine addicts and healthy controls. Our results point toward a transcriptional mechanism whereby cocaine alters specific gene networks in dlPFC neurons. In particular, we identified an AP-1 regulated transcriptional network in dlPFC neurons associated with cocaine use disorder that contains several differentially expressed hub genes. Several of these hub genes are GWAS hits for traits that might involve dysfunction of brain reward circuitry (Body-Mass Index, Obesity) or dlPFC (Bipolar disorder, Schizophrenia). Further study is warranted to determine their potential pathophysiological role in cocaine addiction.

Prefrontal Cortex to Accumbens Projections in Sleep Regulation of Reward

Sleep profoundly affects the emotional and motivational state. In humans and animals, loss of sleep often results in enhanced motivation for reward, which has direct implications for health risks as well as potential benefits. Current study aims at understanding the mechanisms underlying sleep deprivation (SDe)-induced enhancement of reward seeking. We found that after acute SDe, mice had an increase in sucrose seeking and consumption but not food intake, suggesting a selective enhancement of motivation for reward. In the nucleus accumbens (NAc), a key brain region regulating emotional and motivational responses, we observed a decrease in the ratio of the overall excitatory over inhibitory synaptic inputs onto NAc principle neurons after SDe. The shift was partly mediated by reduced glutamatergic transmission of presynaptic origin. Further analysis revealed that there was selective reduction of the glutamate release probability at the medial prefrontal cortex (mPFC)-to-NAc synapses, but not those from the hippocampus, thalamus, or the basal lateral amygdala. To reverse this SDe-induced synaptic alteration, we expressed the stabilized step function opsin (SSFO) in the mPFC; optogenetic stimulation of SSFO at mPFC-to-NAc projection terminals persistently enhanced the action potential-dependent glutamate release. Intra-NAc optogenetic stimulation of SSFO selectively at mPFC-to-NAc terminals restored normal sucrose seeking in mice after SDe without affecting food intake. These results highlight the mPFC-to-NAc projection as a key circuit-based target for sleep to regulate reward-motivated behaviors.

SIGNIFICANCE STATEMENT

Sleep loss, a costly challenge of modern society, has profound physiological and psychological consequences, including altered reward processing of the brain. The current study aims at understanding the mechanisms underlying sleep deprivation-induced enhancement of reward seeking. We identify that the medial prefrontal cortex (mPFC)-to-nucleus accumbens (NAc) glutamatergic transmission is selectively weakened following acute sleep deprivation, whose restoration normalizes reward seeking in sleep-deprived mice. These results suggest a possibility of normalizing sleep deprivation-induced abnormal reward seeking by targeting specific neural projections, and they demonstrate the mPFC-to-NAc glutamatergic projection as a key circuit-based target for sleep to regulate reward-motivated behaviors.

Reward Circuitry in Addiction

Understanding the brain circuitry that underlies reward is critical to improve treatment for many common health issues, including obesity, depression, and addiction. Here we focus on insights into the organization and function of reward circuitry and its synaptic and structural adaptations in response to cocaine exposure. While the importance of certain circuits, such as the mesocorticolimbic dopamine pathway, are well established in drug reward, recent studies using genetics-based tools have revealed functional changes throughout the reward circuitry that contribute to different facets of addiction, such as relapse and craving. The ability to observe and manipulate neuronal activity within specific cell types and circuits has led to new insight into not only the basic connections between brain regions, but also the molecular changes within these specific microcircuits, such as neurotrophic factor and GTPase signaling or α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor function, that underlie synaptic and structural plasticity evoked by drugs of abuse. Excitingly, these insights from preclinical rodent work are now being translated into the clinic, where transcranial magnetic simulation and deep brain stimulation therapies are being piloted in human cocaine dependence. Thus, this review seeks to summarize current understanding of the major brain regions implicated in drug-related behaviors and the molecular mechanisms that contribute to altered connectivity between these regions, with the postulation that increased knowledge of the plasticity within the drug reward circuit will lead to new and improved treatments for addiction.