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The management of patients with severe brain injuries and prolonged disorders of consciousness raises important issues particularly with respect to their therapeutic options. The scarcity of treatment options is challenged by new clinical and neuroimaging data indicating that some patients with prolonged disorders of consciousness might benefit from therapeutic interventions, even years after the injury. Most studies of interventions aimed at improving patients' level of consciousness and functional recovery were behavioural and brain imaging open-label trials and case reports, but several randomised controlled trials have been done, particularly focused on the effects of drugs or use of non-invasive brain stimulation. However, only two studies on amantadine and transcranial direct current stimulation provided class II evidence. Although new therapeutic approaches seem to be valuable for patients with prolonged disorders of consciousness, optimised stimulation parameters, alternative drugs, or rehabilitation strategies still need to be tested and validated to improve rehabilitation and the quality of life of these patients.

While pharmacological, behavioral and psychosocial treatments are available for substance use disorders (SUDs), they are not always effective or well-tolerated. Neuromodulation (NM) methods, including repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS) and deep brain stimulation (DBS) may address SUDs by targeting addiction neurocircuitry. We evaluated the efficacy of NM to improve behavioral outcomes in SUDs. A systematic literature search was performed on MEDLINE, PsychINFO, and PubMed databases and a list of search terms for four key concepts (SUD, rTMS, tDCS, DBS) was applied. Ninety-four studies were identified that examined the effects of rTMS, tDCS, and DBS on substance use outcomes (e.g., craving, consumption, and relapse) amongst individuals with SUDs including alcohol, tobacco, cannabis, stimulants, and opioids. Meta-analyses were performed for alcohol and tobacco studies using rTMS and tDCS. We found that rTMS reduced substance use and craving, as indicated by medium to large effect sizes (Hedge’s g  > 0.5). Results were most encouraging when multiple stimulation sessions were applied, and the left dorsolateral prefrontal cortex (DLPFC) was targeted. tDCS also produced medium effect sizes for drug use and craving, though they were highly variable and less robust than rTMS; right anodal DLPFC stimulation appeared to be most efficacious. DBS studies were typically small, uncontrolled studies, but showed promise in reducing misuse of multiple substances. NM may be promising for the treatment of SUDs. Future studies should determine underlying neural mechanisms of NM, and further evaluate extended treatment durations, accelerated administration protocols and long-term outcomes with biochemical verification of substance use.

Noninvasive brain stimulation techniques are used in experimental and clinical fields for their potential effects on brain network dynamics and behavior. Transcranial electrical stimulation (TES), including transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), has gained popularity because of its convenience and potential as a chronic therapy. However, a mechanistic understanding of TES has lagged behind its widespread adoption. Here, we review data and modelling on the immediate neurophysiological effects of TES in vitro as well as in vivo in both humans and other animals. While it remains unclear how typical TES protocols affect neural activity, we propose that validated models of current flow should inform study design and artifacts should be carefully excluded during signal recording and analysis. Potential indirect effects of TES (e.g., peripheral stimulation) should be investigated in more detail and further explored in experimental designs. We also consider how novel technologies may stimulate the next generation of TES experiments and devices, thus enhancing validity, specificity, and reproducibility. Transcranial electrical stimulation techniques, such as tDCS and tACS, are popular tools for neuroscience and clinical therapy, but how low-intensity current might modulate brain activity remains unclear. In this review, the authors review the evidence on mechanisms of transcranial electrical stimulation.

The ventromedial and dorsolateral prefrontal cortex are two major prefrontal regions that usually interact in serving different cognitive functions. On the other hand, these regions are also involved in cognitive processing of emotions but their contribution to emotional processing is not well-studied. In the present study, we investigated the role of these regions in three dimensions (valence, arousal and dominance) of emotional processing of stimuli via ratings of visual stimuli performed by the study participants on these dimensions. Twenty- two healthy adult participants (mean age 25.21 ± 3.84 years) were recruited and received anodal and sham transcranial direct current stimulation (tDCS) (1.5 mA, 15 min) over the dorsolateral prefrontal cortex (dlPFC) and and ventromedial prefrontal cortex (vmPFC) in three separate sessions with an at least 72-h interval. During stimulation, participants underwent an emotional task in each stimulation condition. The task included 100 visual stimuli and participants were asked to rate them with respect to valence, arousal, and dominance. Results show a significant effect of stimulation condition on different aspects of emotional processing. Specifically, anodal tDCS over the dlPFC significantly reduced valence attribution for positive pictures. In contrast, anodal tDCS over the vmPFC significantly reduced arousal ratings. Dominance ratings were not affected by the intervention. Our results suggest that the dlPFC is involved in control and regulation of valence of emotional experiences, while the vmPFC might be involved in the extinction of arousal caused by emotional stimuli. Our findings implicate dimension-specific processing of emotions by different prefrontal areas which has implications for disorders characterized by emotional disturbances such as anxiety or mood disorders.

Transcranial direct current stimulation (tDCS) is a popular brain stimulation method that is used to modulate cortical excitability, producing facilitatory or inhibitory effects upon a variety of behaviors. There is, however, a current lack of consensus between studies, with many results suggesting that polarity-specific effects are difficult to obtain. This article explores some of these differences and highlights the experimental parameters that may underlie their occurrence. We provide a general, practical snapshot of tDCS methodology, including what it is used for, how to use it, and considerations for designing an effective and safe experiment. Our aim is to equip researchers who are new to tDCS with the essential knowledge so that they can make informed and well-rounded decisions when designing and running successful experiments. By summarizing the varied approaches, stimulation parameters, and outcomes, this article should help inform future tDCS research in a variety of fields.

Transcranial direct current stimulation (tDCS) has been proposed as a new treatment in major depressive disorder (MDD). This is a fully remote, multisite, double-blind, placebo-controlled, randomized superiority trial of 10-week home-based tDCS in MDD. Participants were 18 years or older, with MDD in current depressive episode of at least moderate severity as measured using the Hamilton Depression Rating Scale (mean = 19.07 ± 2.73). A total of 174 participants (120 women, 54 men) were randomized to active ( n  = 87, mean age = 37.09 ± 11.14 years) or sham ( n  = 87, mean age = 38.32 ± 10.92 years) treatment. tDCS consisted of five sessions per week for 3 weeks then three sessions per week for 7 weeks in a 10-week trial, followed by a 10-week open-label phase. Each session lasted 30 min; the anode was placed over the left dorsolateral prefrontal cortex and the cathode over the right dorsolateral prefrontal cortex (active tDCS 2 mA and sham tDCS 0 mA, with brief ramp up and down to mimic active stimulation). As the primary outcome, depressive symptoms showed significant improvement when measured using the Hamilton Depression Rating Scale: active 9.41 ± 6.25 point improvement (10-week mean = 9.58 ± 6.02) and sham 7.14 ± 6.10 point improvement (10-week mean = 11.66 ± 5.96) (95% confidence interval = 0.51–4.01, P  = 0.012). There were no differences in discontinuation rates. In summary, a 10-week home-based tDCS treatment with remote supervision in MDD showed high efficacy, acceptability and safety. ClinicalTrials.gov registration: NCT05202119 A randomized, sham-controlled, superiority trial of a 10-week course of home-based transcranial direct current stimulation found greater improvements in depressive symptoms with active compared to sham stimulation in major depressive disorder.

Transcranial direct current stimulation (tDCS) is a promising method for altering the function of neural systems, cognition, and behavior. Evidence is emerging that it can also influence psychiatric symptomatology, including major depression and schizophrenia. However, there are many open questions regarding how the method might have such an effect, and uncertainties surrounding its influence on neural activity, and human cognition and functioning. In the present critical review, we identify key priorities for future research into major depression and schizophrenia, including studies of the mechanism(s) of action of tDCS at the neuronal and systems levels, the establishment of the cognitive impact of tDCS, as well as investigations of the potential clinical efficacy of tDCS. We highlight areas of progress in each of these domains, including data that appear to favor an effect of tDCS on neural oscillations rather than spiking, and findings that tDCS administration to the prefrontal cortex during task training may be an effective way to enhance behavioral performance. Finally, we provide suggestions for further empirical study that will elucidate the impact of tDCS on brain and behavior, and may pave the way for efficacious clinical treatments for psychiatric disorders.

AbstractObjectiveTo compare the effectiveness of interventions for the management of long covid (post-covid condition).DesignLiving systematic review.Data sourcesMedline, Embase, CINAHL, PsycInfo, Allied and Complementary Medicine Database, and Cochrane Central Register of Controlled Trials from inception to December 2023.Eligibility criteriaTrials that randomised adults (≥18 years) with long covid to drug or non-drug interventions, placebo or sham, or usual care.Results24 trials with 3695 patients were eligible. Four trials (n=708 patients) investigated drug interventions, eight (n=985) physical activity or rehabilitation, three (n=314) behavioural, four (n=794) dietary, four (n=309) medical devices and technologies, and one (n=585) a combination of physical exercise and mental health rehabilitation. Moderate certainty evidence suggested that, compared with usual care, an online programme of cognitive behavioural therapy (CBT) probably reduces fatigue (mean difference −8.4, 95% confidence interval (CI) −13.11 to −3.69; Checklist for Individual Strength fatigue subscale; range 8-56, higher scores indicate greater impairment) and probably improves concentration (mean difference −5.2, −7.97 to −2.43; Checklist for Individual Strength concentration problems subscale; range 4-28; higher scores indicate greater impairment). Moderate certainty evidence suggested that, compared with usual care, an online, supervised, combined physical and mental health rehabilitation programme probably leads to improvement in overall health, with an estimated 161 more patients per 1000 (95% CI 61 more to 292 more) experiencing meaningful improvement or recovery, probably reduces symptoms of depression (mean difference −1.50, −2.41 to −0.59; Hospital Anxiety and Depression Scale depression subscale; range 0-21; higher scores indicate greater impairment), and probably improves quality of life (0.04, 95% CI 0.00 to 0.08; Patient-Reported Outcomes Measurement Information System 29+2 Profile; range −0.022-1; higher scores indicate less impairment). Moderate certainty evidence suggested that intermittent aerobic exercise 3-5 times weekly for 4-6 weeks probably improves physical function compared with continuous exercise (mean difference 3.8, 1.12 to 6.48; SF-36 physical component summary score; range 0-100; higher scores indicate less impairment). No compelling evidence was found to support the effectiveness of other interventions, including, among others, vortioxetine, leronlimab, combined probiotics-prebiotics, coenzyme Q10, amygdala and insula retraining, combined L-arginine and vitamin C, inspiratory muscle training, transcranial direct current stimulation, hyperbaric oxygen, a mobile application providing education on long covid.ConclusionModerate certainty evidence suggests that CBT and physical and mental health rehabilitation probably improve symptoms of long covid.Systematic review registrationOpen Science Framework https://osf.io/9h7zm/.Readers’ noteThis article is a living systematic review that will be updated to reflect emerging evidence. Updates may occur for up to two years from the date of original publication.

Anatomically realistic volume conductor models of the human head are important for accurate forward modeling of the electric field during transcranial brain stimulation (TBS), electro- (EEG) and magnetoencephalography (MEG). In particular, the skull compartment exerts a strong influence on the field distribution due to its low conductivity, suggesting the need to represent its geometry accurately. However, automatic skull reconstruction from structural magnetic resonance (MR) images is difficult, as compact bone has a very low signal in magnetic resonance imaging (MRI). Here, we evaluate three methods for skull segmentation, namely FSL BET2, the unified segmentation routine of SPM12 with extended spatial tissue priors, and the skullfinder tool of BrainSuite. To our knowledge, this study is the first to rigorously assess the accuracy of these state-of-the-art tools by comparison with CT-based skull segmentations on a group of ten subjects. We demonstrate several key factors that improve the segmentation quality, including the use of multi-contrast MRI data, the optimization of the MR sequences and the adaptation of the parameters of the segmentation methods. We conclude that FSL and SPM12 achieve better skull segmentations than BrainSuite. The former methods obtain reasonable results for the upper part of the skull when a combination of T1- and T2-weighted images is used as input. The SPM12-based results can be improved slightly further by means of simple morphological operations to fix local defects. In contrast to FSL BET2, the SPM12-based segmentation with extended spatial tissue priors and the BrainSuite-based segmentation provide coarse reconstructions of the vertebrae, enabling the construction of volume conductor models that include the neck. We exemplarily demonstrate that the extended models enable a more accurate estimation of the electric field distribution during transcranial direct current stimulation (tDCS) for montages that involve extraencephalic electrodes. The methods provided by FSL and SPM12 are integrated into pipelines for the automatic generation of realistic head models based on tetrahedral meshes, which are distributed as part of the open-source software package SimNIBS for field calculations for transcranial brain stimulation. •Assessment of three methods for the automatic skull segmentation from MR images.•Rigorous test of their accuracy by comparison against CT data of the same subjects.•FSL and SPM12 can achieve reasonable accuracy for the upper part of the head.•A combination of T1- and T2-weighted images, rather than a single T1, is suggested.•Accuracy strongly benefits from optimization of the MRI sequence parameters.

Transcranial direct current stimulation (tDCS) has been proposed as a feasible treatment for major depressive disorder (MDD). However, meta-analytic evidence is heterogenous and data from multicentre trials are scarce. We aimed to assess the efficacy of tDCS versus sham stimulation as an additional treatment to a stable dose of selective serotonin reuptake inhibitors (SSRIs) in adults with MDD. The DepressionDC trial was triple-blind, randomised, and sham-controlled and conducted at eight hospitals in Germany. Patients being treated at a participating hospital aged 18–65 years were eligible if they had a diagnosis of MDD, a score of at least 15 on the Hamilton Depression Rating Scale (21-item version), no response to at least one antidepressant trial in their current depressive episode, and treatment with an SSRI at a stable dose for at least 4 weeks before inclusion; the SSRI was continued at the same dose during stimulation. Patients were allocated (1:1) by fixed-blocked randomisation to receive either 30 min of 2 mA bifrontal tDCS every weekday for 4 weeks, then two tDCS sessions per week for 2 weeks, or sham stimulation at the same intervals. Randomisation was stratified by site and baseline Montgomery-Åsberg Depression Rating Scale (MADRS) score (ie, <31 or ≥31). Participants, raters, and operators were masked to treatment assignment. The primary outcome was change on the MADRS at week 6, analysed in the intention-to-treat population. Safety was assessed in all patients who received at least one treatment session. The trial was registered with ClinicalTrials.gov (NCT02530164). Between Jan 19, 2016, and June 15, 2020, 3601 individuals were assessed for eligibility. 160 patients were included and randomly assigned to receive either active tDCS (n=83) or sham tDCS (n=77). Six patients withdrew consent and four patients were found to have been wrongly included, so data from 150 patients were analysed (89 [59%] were female and 61 [41%] were male). No intergroup difference was found in mean improvement on the MADRS at week 6 between the active tDCS group (n=77; –8·2, SD 7·2) and the sham tDCS group (n=73; –8·0, 9·3; difference 0·3 [95% CI –2·4 to 2·9]). Significantly more participants had one or more mild adverse events in the active tDCS group (50 [60%] of 83) than in the sham tDCS group (33 [43%] of 77; p=0·028). Active tDCS was not superior to sham stimulation during a 6-week period. Our trial does not support the efficacy of tDCS as an additional treatment to SSRIs in adults with MDD. German Federal Ministry of Education and Research.