Targeting the biased brain: non-invasive brain stimulation to ameliorate cognitive control

The effect of intermittent theta burst stimulation for cognitive dysfunction: a meta-analysis

BACKGROUND

Growing evidence suggests that cognitive dysfunction significantly impacts patients' quality of life. Intermittent theta burst stimulation (iTBS) has emerged as a potential intervention for cognitive dysfunction. However, consensus on the iTBS protocol for cognitive impairment is lacking.

METHODS

We conducted searches in the Cochrane Central Register of Controlled Trials, EMBASE, PubMed, Chinese National Knowledge Infrastructure, Wanfang Database and the Chongqing VIP Chinese Science and Technology Periodical Database from their inception to January 2024. Random-effects meta-analyzes were used to calculate standardized mean differences and 95% confidence intervals. The quality of evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluation approach.

RESULTS

Twelve studies involving 506 participants were included in the meta-analysis. The analysis showed a trend toward improvement of total cognitive function, activities of daily living and P300 latency compared to sham stimulation in patients with cognitive dysfunction. Subgroup analysis demonstrated that these effects were restricted to patients with post-stroke cognitive impairment but not Alzheimer's disease or Parkinson's disease. Furthermore, subthreshold stimulation also exhibited a significant improvement.

CONCLUSIONS

The results suggest that iTBS may improve cognitive function in patients with cognitive dysfunction, although the quality of evidence remains low. Further studies with better methodological quality should explore the effects of iTBS on cognitive function.

Targeting the left DLPFC and right VLPFC in unmarried romantic relationship breakup (love trauma syndrome) with intensified electrical stimulation: A randomized, single-blind, parallel-group, sham-controlled study

BACKGROUND

Ending a romantic relationship is one of the most painful losses an adult experience. Neuroimaging studies suggest that there is a neuropsychological link between breakup experiences and bereaved individuals, and that specific prefrontal regions are involved. The aim of this study was to determine whether enhancement of left DLPFC and right VLPFC activity with a novel intensified anodal transcranial direct current stimulation protocol reduces core symptoms of love trauma syndrome (LTS) and improves treatment-related variables.

METHODS

In this randomized, sham-controlled, single-blind parallel trial, we assessed the efficacy of an intensified anodal stimulation protocol (20 min, twice-daily sessions with 20 min intervals, 5 consecutive days) with two montages (left DLPFC vs right VLPFC) to reduce love trauma symptoms. 36 participants with love trauma syndrome were randomized in three tDCS condition (left DLPFC, right VLPFC, sham stimulation). LTS symptoms, treatment-related outcome variables (depressive state, anxiety, emotion regulation, positive and negative affect), and cognitive functions were assessed before, right after, and one month after intervention.

RESULTS

Both DLPFC and VLPFC protocols significantly reduced LTS symptoms, and improved depressive state and anxiety after the intervention, as compared to the sham group. The improving effect of the DLPFC protocol on love trauma syndrome was significantly larger than that of the VLPFC protocol. For emotion regulation and positive and negative affect, improved regulation of emotions and positive affect and reduced negative affect were revealed after intervention in the two real stimulation conditions compared to the sham. For cognitive functions, no significant difference was observed between the groups, but again a positive effect of intervention within groups in the real stimulation conditions (DLPFC and VLPFC) was found for most components of the cognitive tasks.

CONCLUSIONS

Enhancement of left DLPFC and right VLPFC activity with intensified stimulation improves LTS symptoms and treatment-related variables. For LTS symptoms, DLPFC stimulation was more efficient than VLPFC stimulation., For the other variables, no significant difference was observed between these two stimulation groups. These promising results require replication in larger trials.

Inhibitory Control in Young Healthy Adults - a tDCS Study

Inhibitory control plays a role in the behavior selection and detection of conflicts. Defects in inhibitory control are an integral part of many neuropsychiatric disorders and the possibilities of influencing it are the subject of active study. Studies have shown and confirmed the activation of the dorsolateral prefrontal cortex (DLPFC) during the Stroop task and other tests involving response inhibition. Non-invasive brain stimulation is an emerging and actively developing group of methods used in cognitive research. In the present study, we used non-invasive, painless, and delicate transcranial direct stimulation (tDCS) for the study of inhibitory control, and to explore the effect of impulsivity on response inhibition ability in young healthy participants. We conducted a cross-over study with cross-hemispheric application of 2 mA tDCS with electrodes placed on the right - cathode, and left - anode - DLPFC. Participants performed a classic Stroop test before and after stimulation. Impulsivity was measured via the personal impulsiveness questionnaire. There was no significant difference in interference score alteration between active and sham stimulations, anodal and sham tDCS both induced slight improvement in Stroop test results. Individual impulsivity in healthy participants showed no influence on their results. Our study adds to the picture and helps to deepen knowledge about the impact of different stimulation parameters on cognitive functions.

Transcranial direct current stimulation as an additional treatment to selective serotonin reuptake inhibitors in adults with major depressive disorder in Germany (DepressionDC): a triple-blind, randomised, sham-controlled, multicentre trial

BACKGROUND

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.

METHODS

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).

FINDINGS

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).

INTERPRETATION

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.

FUNDING

German Federal Ministry of Education and Research.

Combining transcranial direct current stimulation with group cognitive behavioral therapy developed to treat rumination: a clinical pilot study

Background

As part of repetitive negative thinking (RNT), rumination is a maladaptive cognitive response style to stress or negative mood which can increase the risk of depression and may prohibit complete recovery. Cognitive behavioral therapy (CBT) and transcranial direct current stimulation (tDCS) both proved to be effective in decreasing rumination. However, the combined effects of tDCS and CBT interventions on rumination have not yet been explored. The first aim of this pilot study is to investigate whether the combination of tDCS and CBT has an accumulating positive effect on modulating state rumination. The second aim is to assess the feasibility and safety profile of the proposed combined approach.

Method

Seventeen adults aged 32-60 years, suffering from RNT, were referred by their primary care professional to participate in an 8-week group intervention for RNT ("Drop It") comprising 8 sessions of CBT. Before each CBT session, patients underwent one double-blinded prefrontal active (2 mA for 20 min) or sham tDCS (anode over F3, cathode over the right supraorbital region) combined with an internal cognitive attention task focused on individual RNT, i.e., online tDCS priming. During each session, the Brief State Rumination Inventory was used to assess state rumination.

Results

A mixed effects model analysis revealed no significant differences between the stimulation conditions, weekly sessions, or their interaction in terms of state rumination scores.

Conclusion

Overall, the combination of online tDCS priming followed by group CBT was found to be safe and feasible. On the other hand, no significant additional effects of this combined approach on state rumination were established. Although our pilot study may have been too small to find significant clinical effects, future larger RCT studies on combined tDCS-CBT treatment protocols may reevaluate the selection of internal cognitive attention tasks and more objective neurophysiological measurements, consider the optimal timing of the combination (concurrently or sequentially), or may add additional tDCS sessions when following CBT.

Emerging therapeutic targets for anorexia nervosa

INTRODUCTION

Anorexia nervosa is a frequent eating disorder that affects predominantly young women and may take a severe and chronically worsening course of disease contributing to its high mortality rate. Although a multitude of treatment options exist, this disease still bears a high relapse rate. In light of these facts, an improvement of existing and development of new treatment targets and options is warranted.

AREAS COVERED

The present review article covers recent developments in psychotherapy associated with the respective neuropsychological and brain alterations as well as highlights current and future pharmacotherapeutic options.

EXPERT OPINION

Several encouraging developments in the field of psychotherapy such as interventions targeting neurocognitive profiles or addressing reward processing, brain stimulation as well as pharmacological modulation of hormones, namely leptin, oxytocin, ghrelin and nesfatin-1 signaling might be - most likely as part of a multimodal treatment approach - efficacious in order to improve treatment of patients with anorexia nervosa, especially those with a severe course of disease as well as comorbidities. As anorexia nervosa represents a complex and severe mental disorder, it seems most likely that a combination and integration of different evidence-based treatment approaches and settings will contribute to an improved prognosis of this eating disorder. This should be further explored in future studies.

Effects of bilateral sequential theta-burst stimulation on functional connectivity in treatment-resistant depression: First results

BACKGROUND

Previous studies suggest that transcranial magnetic stimulation exerts antidepressant effects by altering functional connectivity (FC). However, knowledge about this mechanism is still limited. Here, we aimed to investigate the effect of bilateral sequential theta-burst stimulation (TBS) on FC in treatment-resistant depression (TRD) in a sham-controlled longitudinal study.

METHODS

TRD patients (n = 20) underwent a three-week treatment of intermittent TBS of the left and continuous TBS of the right dorsolateral prefrontal cortex (DLPFC). Upon this trial's premature termination, 15 patients had received active TBS and five patients sham stimulation. Resting-state functional magnetic resonance imaging was performed at baseline and after treatment. FC (left and right DLPFC) was estimated for each participant, followed by group statistics (t-tests). Furthermore, depression scores were analyzed (linear mixed models analysis) and tested for correlation with FC.

RESULTS

Both groups exhibited reductions of depression scores, however, there was no significant main effect of group, or group and time. Anticorrelations between DLPFC and the subgenual cingulate cortex (sgACC) were observed for baseline FC, corresponding to changes in depression severity. Treatment did not significantly change DLPFC-sgACC connectivity, but significantly reduced FC between the left stimulation target and bilateral anterior insula.

CONCLUSIONS

Our data is compatible with previous reports on the relevance of anticorrelation between DLPFC and sgACC for treatment success. Furthermore, FC changes between left DLPFC and bilateral anterior insula highlight the effect of TBS on the salience network.

LIMITATIONS

Due to the limited sample size, results should be interpreted with caution and are of exploratory nature.

The use of transcutaneous Vagal Nerve Stimulation as an effective countermeasure for Simulator Adaptation Syndrome

This research focused on investigating the effectiveness of Transcutaneous Vagal Nerve Stimulation (tVNS) as compared to Galvanic Cutaneous Stimulation (GCS) at mitigating Simulator Adaptation Syndrome (SAS). Fifty drivers (mean age = 23.04 ± 17.71 years old, twenty-two men) participated in a driving simulation experiment. The total scores of the Simulator Sickness Questionnaire, head movements (body balance index), and driving performance variables were measured under five stimulation conditions: i) baseline (no stimulation delivered), ii) sham GCS, iii) sham tVNS, iv) active GCS, and v) active tNVS. The results showed that tVNS alleviated SAS and improved driving performance variables more effectively than GCS. We conclude that GCS and tVNS have similar neurological mechanisms to reduce SAS, providing possible explanations for the greater effectiveness of tVNS. We encourage the use of tVNS to decrease SAS.

A systematic review on the potential use of machine learning to classify major depressive disorder from healthy controls using resting state fMRI measures

BACKGROUND

Major Depressive Disorder (MDD) is a psychiatric disorder characterized by functional brain deficits, as documented by resting-state functional magnetic resonance imaging (rs-fMRI) studies.

AIMS

In recent years, some studies used machine learning (ML) approaches, based on rs-fMRI features, for classifying MDD from healthy controls (HC). In this context, this review aims to provide a comprehensive overview of the results of these studies.

DESIGN

The studies research was performed on 3 online databases, examining English-written articles published before August 5, 2022, that performed a two-class ML classification using rs-fMRI features. The search resulted in 20 eligible studies.

RESULTS

The reviewed studies showed good performance metrics, with better performance achieved when the dataset was restricted to a more homogeneous group in terms of disease severity. Regions within the default mode network, salience network, and central executive network were reported as the most important features in the classification algorithms.

LIMITATIONS

The small sample size together with the methodological and clinical heterogeneity limited the generalizability of the findings.

CONCLUSIONS

In conclusion, ML applied to rs-fMRI features can be a valid approach to classify MDD and HC subjects and to discover features that can be used for additional investigation of the pathophysiology of the disease.

Gamification improves antidepressant effects of cognitive control training-A pilot trial

OBJECTIVE

Computerised cognitive trainings have been put forward to improve control over negatively biased information processing and associated depressive symptomatology. Yet, disease-related impairments of motivation and endurance, as well as insufficient accessibility hinder use of this promising therapeutic opportunity. Here, we developed an app (de:)press^© ) that utilizes a cognitive control training (paced auditory serial addition task) enriched with gamification and information elements. We compared a six-week training with de:)press^© to a non-gamified version (active control group).

METHODS

Thirty-two depressed participants were included. Each received either de:)press^© or the non-gamified version and was instructed to train three times per week for two weeks. Afterwards (four weeks) they were free to train at their own discretion. Depression severity was assessed during training and two follow-up sessions. Primary endpoint was defined as difference between groups [change of Montgomery-Åsberg Depression Rating Scale (MADRS)] four weeks after end of training.

RESULTS

Depression severity decreased in both groups. At primary endpoint, MADRS scores were significantly lower in the de:)press^© -group compared to the control group. No differences were observed at three months' follow-up. Intervention usability was consistently rated positively. Participants who had trained with de:)press^© maintained the recommended training frequency without further prompting. Besides transient fatigue or frustration, no adverse effects were observed.

CONCLUSION

This pilot demonstrates that gamification and information elements can substantially increase cognitive control training efficacy in alleviating depressive symptoms. Moreover, it provides first evidence for the feasibility and efficacy of de:)press^© as an add-on intervention to treat depression.

CLINICAL TRIAL REGISTRATION

The study is registered under ClinicalTrials.gov, identifier: NCT04400162.

Non-invasive brain stimulation for osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease, the prevalence of OA is increasing, and the elderly are the most common in patients with OA. OA has a severe impact on the daily life of patients, this increases the demand for treatment of OA. In recent years, the application of non-invasive brain stimulation (NIBS) has attracted extensive attention. It has been confirmed that NIBS plays an important role in regulating cortical excitability and oscillatory rhythm in specific brain regions. In this review, we summarized the therapeutic effects and mechanisms of different NIBS techniques in OA, clarified the potential of NIBS as a treatment choice for OA, and provided prospects for further research in the future.

Quantitative description of the relationship between the enhancement of distraction-suppression and brain local state alteration after transcranial direct current stimulation

Anodal transcranial direct current stimulation (tDCS) over the left dorsal lateral prefrontal cortex (lDLPFC) can improve distraction suppression ability, possibly by distantly regulating the connection properties of several large-scale brain networks and local brain state changes. However, little is known about the local state alteration that tDCS can induce in distant but task-related regions and the relationship between performance enhancement and local state alteration in potentially related regions, resulting in inefficient and uncertain tDCS regulation. We aimed to examine the alteration of brain local state before and after tDCS and its relationship with performance enhancement. With the within-subject design, the participants received anodal (1.5 mA) and sham tDCS at F3 (lDLPFC) for 20 min. The visual search task and resting-state functional magnetic resonance imaging (rsfMRI) were performed before and after stimulation. Anodal tDCS significantly enhanced distraction suppression. The amplitude of low-frequency fluctuation (ALFF) in the left parietal region significantly decreased, the decrement significantly positively correlated with performance enhancement after anodal tDCS. As well, the regional homogeneity (ReHo) in the left precuneus significantly increased, and the increasement significantly positively correlated with performance enhancement. Anodal tDCS over the lDLPFC can distantly modulate the local state of the brain and improve the distraction suppression ability. These two aspects are closely related and provide a direct and efficient approach to enhancing performance.

Correlation between cognitive deficits and dorsolateral prefrontal cortex functional connectivity in first-episode depression

INTRODUCTION

Although depression is commonly accompanied by cognitive deficits, the underlying mechanism remains unclear. One possibility is that such deficits are related to abnormal brain network connections. The purpose of this study was thus to investigate changes in brain functional connectivity (FC) in depression and its relationship with cognitive deficits.

METHODS

We enrolled 37 first-episode MDD patients and 53 matched healthy controls (HC). All participants completed clinical and neurocognitive assessments and underwent resting-state functional MRI. Seed-based analysis was used to define the dorsolateral prefrontal cortex (DLPFC) and FC analysis was then performed. We used bias correlation to analyze the correlation between FC and clinical and neurocognitive scores.

RESULTS

MDD patients showed increased FC of the right DLPFC with the left inferior temporal gyrus, left cuneus, right inferior frontal gyrus, right anterior cingulate cortex, left BA39, right angular gyrus, right precuneus, left middle frontal gyrus, and right precentral gyrus. MDD patients also showed stronger FC in the left thalamus and reduced FC between the left superior occipital gyrus and left DLPFC seed region. Interestingly, increased FC was related to disease severity (with the right precentral gyrus) and social cognitive dysfunction (with the right angular gyrus) in MDD patients.

LIMITATIONS

The sample size was relatively small and it is unclear how age may influence FC changes in patients with depression.

CONCLUSIONS

These findings support changes in FC of the DLPFC in early MDD patients related to cognitive function. FC is a potential biomarker for the diagnosis of MDD.

Ethics in psychosurgery

Ethical problems of psychosurgery are debated since 1970s. The issues of informed consent, political and commercial abuses, lacking evidence and needed regulation are overviewed. New surgical techniques provoke new discussions on goals and limits of psychosurgery.

Ameliorating cognitive control in patients with binge eating disorder by electrical brain stimulation: study protocol of the randomized controlled ACCElect pilot trial

BACKGROUND

The current first-line treatment for binge eating disorder (BED), which is psychotherapy, is moderately effective in terms of abstinence from binge-eating. Neurobiological evidence suggests that people affected by BED show difficulties along the spectrum of impulsivity, including inhibitory control impairments and highlights the potential of novel treatment approaches directly targeting inhibitory control, including cognitive training approaches and non-invasive brain stimulation.

METHODS

ACCElect is a prospective, randomized controlled pilot trial investigating a novel, food-related inhibitory control training combined with transcranial direct current stimulation (tDCS). 40 patients with BED will be randomly assigned to receive the training either combined with verum or with sham stimulation (control condition). The inhibitory control training is based on principles of the antisaccade paradigm and comprises six training sessions over two weeks. Core aims are the investigation of feasibility and clinically relevant effects of a tDCS-enhanced inhibitory control training in BED patients and the establishment of a data basis for a larger efficacy trial. The primary clinical endpoint is binge-eating (BE) frequency in terms of changes in BE episodes four weeks after treatment termination as compared to baseline. Key secondary outcomes comprise ED pathology and general psychopathology, inhibitory control capacities, quality of life as well as acceptability and satisfaction with the intervention.

DISCUSSION

The results of the present trial will contribute to the development of novel neurobiologically informed treatment approaches for patients suffering from BED. Trial registration The ACCElect trial was prospectively registered on October 1, 2020, under the registration number NCT04572087 at ClinicalTrials.gov ( https://clinicaltrials.gov/ct2/show/NCT04572087 ).

[Non-Invasive Brain Stimulation in Psychiatric Disorders]

Based on neurophysiological findings, non-invasive brain stimulation methods offer an integrative treatment approach for mental disorders. Some of the stimulation methods have already been extensively studied for specific psychiatric indications and have become established as reasonable treatment option. For example, transcranial magnetic stimulation (TMS) for the treatment of refractory depression received approval from the Food and Drug Administration (FDA) in the United States in 2008. However, in Europe and especially in Germany, TMS is not widely offered even in a university setting. The following article describes the available technologies and their biological mechanisms of action, outlines the clinical indication and application of TMS, and summarizes the clinical evidence. The article is based on recently published guidelines for the therapeutic use of non-invasive brain stimulation 1 2 3.

Baseline-dependent effect of dopamine's precursor L-tyrosine on working memory gating but not updating

Adaptive goal-directed behavior requires a dynamic balance between maintenance and updating within working memory (WM). This balance is controlled by an input-gating mechanism implemented by dopamine in the basal ganglia. Given that dopaminergic manipulations can modulate performance on WM-related tasks, it is important to gain mechanistic insight into whether such manipulations differentially affect updating (i.e., encoding and removal) and the closely-related gate opening/closing processes that respectively enable/prevent updating. To clarify this issue, 2.0 g of dopamine’s precursor L-tyrosine was administered to healthy young adults (N = 45) in a double-blind, placebo-controlled, within-subjects study. WM processes were empirically distinguished using the reference-back paradigm, which isolates performance related to updating, gate opening, and gate closing. L-tyrosine had a selective, baseline-dependent effect only on gate opening, which was evidenced by markedly reduced variance across subjects in gate opening performance in the L-tyrosine compared with the placebo condition, whereas the whole-sample average performance did not differ between conditions. This indicates a pattern of results whereby low-performing subjects improved, whereas high-performing subjects were impaired on L-tyrosine. Importantly, this inverted U-shaped pattern was not explained by regression to the mean. These results are consistent with an inverted-U relationship between dopamine and WM, and they indicate that updating and gating are differentially affected by a dopaminergic manipulation. This highlights the importance of distinguishing these processes when studying WM, for example, in the context of WM deficits in disorders with a dopaminergic pathophysiology.

Cognitive outcomes of the bipolar depression electrical treatment trial (BETTER): a randomized, double-blind, sham-controlled study

Bipolar depression is associated with marked cognitive deficits. Pharmacological treatments for this condition are limited and may aggravate depressive and cognitive symptoms. Therefore, therapeutic interventions that preserve adequate cognitive functioning are necessary. Our previous results demonstrated significant clinical efficacy of transcranial direct current stimulation (tDCS) in the Bipolar Depression Electrical Treatment Trial (BETTER). Here, cognitive outcomes of this study are reported. We randomized 59 patients with bipolar disorder I or II in an acute depressive episode to receive active (12 2 mA, 30-min, anodal-left, cathodal-right prefrontal cortex tDCS sessions) or sham tDCS. Patients were on stable pharmacological regimen for at least 2 weeks. A battery of 12 neuropsychological assessments in five cognitive domains (attention and processing speed, memory, language, inhibitory control, and working memory and executive function) was performed at baseline, after two weeks and at endpoint (week 6). No significant differences between groups over 6 weeks of treatment were observed for any cognitive outcomes. Moreover, no decrease in cognitive performance was observed. Our findings warrant further replication in larger studies. Trial Registration: clinicaltrials.gov Identifier: NCT02152878.

Treatment of major depressive disorder with bilateral theta burst stimulation: study protocol for a randomized, double-blind, placebo-controlled multicenter trial (TBS-D)

Repetitive transcranial magnetic stimulation (rTMS) of the dorsolateral prefrontal cortex (dlPFC) is currently evolving as an effective and safe therapeutic tool in the treatment of major depressive disorder (MDD). However, already established rTMS treatment paradigms are rather time-consuming. With theta burst stimulation (TBS), a patterned form of rTMS, treatment time can be substantially reduced. Pilot studies and a randomized controlled trial (RCT) demonstrate non-inferiority of TBS to 10 Hz rTMS and support a wider use in MDD. Still, data from placebo-controlled multicenter RCTs are lacking. In this placebo-controlled multicenter study, 236 patients with MDD will be randomized to either intermittent TBS (iTBS) to the left and continuous TBS (cTBS) to the right dlPFC or bilateral sham stimulation (1:1 ratio). The treatment will be performed with 80% resting motor threshold intensity over six consecutive weeks (30 sessions). The primary outcome is the treatment response rate (Montgomery-Asberg Depression Rating Scale reduction ≥ 50%). The aim of the study is to confirm the superiority of active bilateral TBS compared to placebo treatment. In two satellite studies, we intend to identify possible MRI-based and (epi-)genetic predictors of responsiveness to TBS therapy. Positive results will support the clinical use of bilateral TBS as an advantageous, efficient, and well-tolerated treatment and pave the way for further individualization of MDD therapy.Trial registration: ClinicalTrials.gov (NCT04392947).

Task and Non-task Brain Activation Differences for Assessment of Depression and Anxiety by fNIRS

Diagnosis and treatment of the patients with major depression (MD) or the combined anxiety and depression (A&D) depend on the questionnaire, sometimes accompanied by tasks such as verbal fluency task (VFT). Functional near infrared spectroscopy (fNIRS) is emerging as an auxiliary diagnostic tool to evaluate brain function, providing an objective criterion to judge psychoses. At present, the conclusions derived from VFT or rest (non-task) studies are controversial. The purpose of this study is to evaluate if task performs better than non-task in separating healthy people from psychiatric patients. In this study, healthy controls (HCs) as well as the patients with MD or A&D were recruited (n = 10 for each group) to participate in the non-task and VFT tasks, respectively, and the brain oxygenation was longitudinally evaluated by using fNIRS. An approach of spectral analysis is used to analyze cerebral hemoglobin parameters (i.e., Oxy and Deoxy), characterizing the physiological fluctuations in the non-task and task states with magnitude spectrum and average power. Moreover, the standard deviation of oxygenation responses during the non-task was compared with the peak amplitude during the task, with the aim to explore the sensitivity of the VFT task to brain activation. The results show that there is no significant difference (p > 0.05) among the three groups in average power during non-task. The VFT task greatly enhanced the magnitude spectrum, leading to significant difference (p < 0.05) in average power between any of two groups (HC, MD, and A&D). Moreover, 40% patients with A&D have an intermediate peak (around 0.05 Hz) in the magnitude spectrum when performing the VFT task, indicating its advantage in characterizing A&D. We defined a rate of the non-task standard variation to the task peak amplitude (namely, SD-to-peak rate) and found that this rate is larger than 20% in 90% of the MD subjects. By contrast, only 40% HC subjects have an SD-to-peak rate larger than 20%. These results indicate that the non-task may not be sufficient to separate MD or A&D from HC. The VFT task could enhance the characteristics of the magnitude spectrum, but its intensity needs to be elevated so as to properly explore brain functions related to psychoses.

The influence of tDCS intensity on decision-making training and transfer outcomes

Transcranial direct current stimulation (tDCS) has been shown to improve single- and dual-task performance in healthy participants and enhance transferable training gains following multiple sessions of combined stimulation and task practice. However, it has yet to be determined what the optimal stimulation dose is for facilitating such outcomes. We aimed to test the effects of different tDCS intensities, with a commonly used electrode montage, on performance outcomes in a multisession single/dual-task training and transfer protocol. In a preregistered study, 123 participants, who were pseudorandomized across four groups, each completed six sessions (pre- and posttraining sessions and four combined tDCS and training sessions) and received 20 min of prefrontal anodal tDCS at 0.7, 1.0, or 2.0 mA or 15-s sham stimulation. Response time and accuracy were assessed in trained and untrained tasks. The 1.0-mA group showed substantial improvements in single-task reaction time and dual-task accuracy, with additional evidence for improvements in dual-task reaction times, relative to sham performance. This group also showed near transfer to the single-task component of an untrained multitasking paradigm. The 0.7- and 2.0-mA intensities varied in which performance measures they improved on the trained task, but in sum, the effects were less robust than for the 1.0-mA group, and there was no evidence for the transfer of performance. Our study highlights that training performance gains are augmented by tDCS, but their magnitude and nature are not uniform across stimulation intensity.NEW & NOTEWORTHY Using techniques such as transcranial direct current stimulation to modulate cognitive performance is an alluring endeavor. However, the optimal parameters to augment performance are unknown. Here, in a preregistered study with a large sample (123 subjects), three different stimulation dosages (0.7, 1.0, and 2.0 mA) were applied during multitasking training. Different cognitive training performance outcomes occurred across the dosage conditions, with only one of the doses (1.0 mA) leading to training transfer.

Please, don't do it! Fifteen years of progress of non-invasive brain stimulation in action inhibition

The ability to inhibit prepotent responses is critical for survival. Action inhibition can be investigated using a stop-signal task (SST), designed to provide a reliable measure of the time taken by the brain to suppress motor responses. Here we review the major research advances using the combination of this paradigm with the use of non-invasive brain stimulation techniques in the last fifteen years. We highlight new methodological approaches to understanding and exploiting several processes underlying action control, which is critically impaired in several psychiatric disorders. In this review we present and discuss existing literature demonstrating i) the importance of the use of non-invasive brain stimulation in studying human action inhibition, unveiling the neural network involved ii) the critical role of prefrontal areas, including the pre-supplementary motor area (pre-SMA) and the inferior frontal gyrus (IFG), in inhibitory control iii) the neural and behavioral evidence of proactive and reactive action inhibition. As the main result of this review, the specific literature demonstrated the crucial role of pre-SMA and IFG as evidenced from the field of noninvasive brain stimulation studies. Finally, we discuss the critical questions that remain unanswered about how such non-invasive brain stimulation protocols can be translated to therapeutic treatments.

Effects of 1 mA and 2 mA transcranial direct current stimulation on working memory performance in healthy participants

Anodal transcranial current stimulation (tDCS) to the left dorsolateral prefrontal cortex (DLPFC) has been shown to enhance working memory (WM) in neuropsychiatric patients. In healthy populations, however, tDCS obtains inconclusive results, mostly due to heterogeneous study and stimulation protocols. Here, we approached these issues by investigating effects of tDCS intensity on simultaneous WM performance with three cognitive loads by directly comparing findings of two double-blind, cross-over, sham-controlled experiments. TDCS was administrated to the left DLPFC at intensity of 1 mA (Experiment 1) or 2 mA (Experiment 2), while participants completed a verbal n-back paradigm (1-, 2-, 3-back). Analysis showed no overall effects of tDCS on WM, but a significant interaction with cognitive load. The present study suggests that cognitive load rather than tDCS intensity could be a decisive factor for effects on WM. Moreover, it emphasizes the need of thorough investigation on study parameters to develop more efficient stimulation protocols.

Systematic review of combined functional near-infrared spectroscopy and transcranial direct-current stimulation studies

Significance: Combining transcranial direct-current stimulation (tDCS) with functional near-infrared spectroscopy (fNIRS) is a recent approach to exploring brain activation evoked by neurostimulation. Aim: To critically evaluate studies combining tDCS and fNIRS and provide a consolidated overview of cortical hemodynamic responses to neurostimulation. Approach: Key terms were searched in three databases (MEDLINE, EMBASE, and PsycINFO) with cross-referencing and works from Google Scholar also evaluated. All studies reporting on fNIRS-derived hemoglobin changes evoked by tDCS were included. Results: Literature searches revealed 474 articles, of which 28 were included for final review (22 in healthy individuals: 9 involving rest and 13 with tasks; 6 in the clinical setting). At rest, an overall increase in cortical activation was observed in fNIRS responses at the site of stimulation, with evidence suggesting nonstimulated brain regions are also similarly affected. Conversely, during tasks, reduced cortical activation was observed during online stimulation. Offline and poststimulation effects were less consistent, as is the impact on clinical populations and their symptom correlation. Conclusion: This review explores the methodological frameworks for fNIRS-tDCS evaluations and summarizes hemodynamic responses associated with tDCS in all populations. Our findings provide further evidence of the impact of tDCS on neuronal activation within functionally connected networks.

The Effect of Cerebellar tDCS on Sequential Motor Response Selection

Transcranial direct current stimulation (tDCS) transiently alters cortical excitability and synaptic plasticity. So far, few studies have investigated the behavioral effects of applying tDCS to the cerebellum. Given the cerebellum's inhibitory effects on cortical motor areas as well as its role in fine motor control and motor coordination, we investigated whether cerebellar tDCS can modulate response selection processes and motor sequence learning. Seventy-two participants received either cerebellar anodal (excitatory), cathodal (inhibitory), or sham (placebo) tDCS while performing a serial reaction time task (SRTT). To compare acute and long-term effects of stimulation on behavioral performance, participants came back for follow-up testing at 24 h after stimulation. Results indicated no group differences in performance prior to tDCS. During stimulation, tDCS did not affect sequence-specific learning, but anodal as compared to cathodal and sham stimulations did modulate response selection processes. Specifically, anodal tDCS increased response latencies independent of whether a trained or transfer sequence was being performed, although this effect became smaller throughout training. At the 24-h follow-up, the group that previously received anodal tDCS again demonstrated increased response latencies, but only when the previously trained sequence and a transfer sequence had to be performed in the same experimental block. This increased behavioral interference tentatively points to a detrimental effect of anodal cerebellar tDCS on sequence consolidation/retention. These results are consistent with the notion that the cerebellum exerts an inhibitory effect on cortical motor areas, which can impair sequential response selection when this inhibition is strengthened by tDCS.

Clinical review: The therapeutic use of theta-burst stimulation in mental disorders and tinnitus

Repetitive Transcranial Magnetic Stimulation (rTMS) is a neuromodulatory treatment intervention, which can be used to alleviate symptoms of mental disorders. Theta-burst stimulation (TBS), an advanced, patterned form of TMS, features several advantages regarding applicability, treatment duration and neuroplastic effects. This clinical review summarizes TBS studies in mental disorders and tinnitus and discusses effectivity and future directions of clinical TBS research. Following the PRISMA guidelines, the authors included 47 studies published until July 2018. Particularly in depression, evidence for the effectiveness of TBS and non-inferiority to conventional rTMS exists. Evidence for therapeutic efficacy of TBS in other mental disorders remains weak due to a large heterogeneity between studies. Rigorous reporting standards and adequately powered controlled trials are indispensable to foster validity and translation into clinical use. Nevertheless, TBS remains a promising instrument to target maladaptive brain networks and to ameliorate psychiatric symptoms.

Improvement of cognitive control and stabilization of affect by prefrontal transcranial direct current stimulation (tDCS)

Cognitive control of information processing is an essential prerequisite of human behavior. Particularly, focusing attention in the face of failure poses a common challenge. Previous work has demonstrated that transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex (dlPFC) can improve cognitive control in a challenging and repeatedly frustrating task. In a randomized, sham-controlled, crossover design 22 healthy, male participants performed an adaptive 2-back version of the Paced Auditory Serial Addition Task (PASAT), parallel to anodal or sham tDCS over the left dlPFC and the return electrode on the right upper arm. Before and after the 2-back PASAT, the affective state was assessed by means of the Positive and Negative Affective Schedule (PANAS). We observed an interaction between stimulation condition and task performance driven by an increase in performance with anodal tDCS and no improvement with sham stimulation. In addition, after the 2-back PASAT we found a higher positive and a trend towards lower negative affect with anodal as compared to sham tDCS. Our data support and extend previous results showing improved processing speed under anodal stimulation associated with a reduced task-induced negative affect indicating an improvement of cognitive control. Further studies will investigate long-term effects and clinical applicability.

Effects of music therapy on major depressive disorder: A study of prefrontal hemodynamic functions using fNIRS

Major depressive disorder (MDD) is a recurrent, chronic mental illness. While music therapy has been established as an effective treatment for MDD patients, the effects of this therapy on brain function remain unclear. This research employed near-infrared spectroscopy (NIRS) to explore the effects of music therapy on brain activity in mild or moderate MDD patients and to illustrate the potential mechanism of music therapy. Methods: Fifteen MDD patients and fifteen healthy controls (HC) underwent neuropsychological evaluations and NIRS measurements. All participants were treated with continuous music therapy for 10 days. Subsequently, all individuals were evaluated with neuropsychological assessments and NIRS measurements again. Results: The verbal fluency task (VFT) performances of the participants yielded significantly higher scores after music therapy in terms of vegetables, four-footed animals and fruit blocks. After the music treatment, the NIRS data showed that the mean active oxy-Hb values of channels 21, 23, 19, and 41 were significantly increased in both the MDD and HC groups. The MDD group showed significant activation in the dorsolateral prefrontal cortex (DLPFC), orbitofrontal cortex (OFC) and ventromedial prefrontal cortex (VMPFC) after music therapy. The results indicate that music therapy could improve the brain function of MDD patients.

Improving working memory in schizophrenia: Effects of 1 mA and 2 mA transcranial direct current stimulation to the left DLPFC

Deficits in various cognitive processes, such as working memory, are characteristic for schizophrenia, lowering patients' functioning and quality of life. Recent research suggests that transcranial direct stimulation (tDCS) applied to the dorsolateral prefrontal cortex (DLPFC) may be a potential therapeutic intervention for cognitive deficits in schizophrenia. Here, we examined the effects of online tDCS to the DLPFC on working memory (WM) performance in 40 schizophrenia patients in two separate experiments with a double blind, sham-controlled, cross-over design. Patients underwent single sessions of active and sham tDCS in a randomized order. Stimulation parameters were anode F3, cathode right deltoid muscle, 21 min tDCS duration, 1 mA tDCS in Experiment 1 (N = 20) and 2 mA tDCS in Experiment 2 (N = 20). Primary outcome was the change in WM performance as measured by a verbal n-back paradigm (1- to 3-back). Irrespective of the stimulation intensity, data analysis showed a significant higher WM accuracy during active tDCS than during sham tDCS (p = 0.019), but no main effect of stimulation intensity (p = 0.392). Subsequent separate analyses revealed a significantly improved WM performance only during 1 mA (p = 0.048). TDCS facilitated WM functioning in schizophrenia, with an advantage of 1 mA over 2 mA. Our results support the notion that tDCS may be a potential treatment for cognitive deficits in schizophrenia and emphasize the need for future research on the specific stimulation parameters.

Transcutaneous Vagus Nerve Stimulation (tVNS) Enhances Response Selection During Sequential Action

Transcutaneous vagus nerve stimulation (tVNS) is a non-invasive and safe technique that transiently enhances brain GABA and noradrenaline levels. Although tVNS has been used mainly to treat clinical disorders such as epilepsy, recent studies indicate it is also an effective tool to investigate and potentially enhance the neuromodulation of action control. Given the key roles of GABA and noradrenaline in neural plasticity and cortical excitability, we investigated whether tVNS, through a presumed increase in level of these neurotransmitters, modulates sequential behavior in terms of response selection and sequence learning components. To this end we assessed the effect of single-session tVNS in healthy young adults (N = 40) on performance on a serial reaction time task, using a single-blind, sham-controlled between-subject design. Active as compared to sham tVNS did not differ in terms of acquisition of an embedded response sequence and in terms of performance under randomized response schedules. However, active tVNS did enhance response selection processes. Specifically, the group receiving active tVNS did not exhibit inhibition of return during response reversals (i.e., when trial N requires the same response as trial N-2, e.g., 1-2-1) on trials with an embedded response sequence. This finding indicates that tVNS enhances response selection processes when selection demands are particularly high. More generally, these results add to converging evidence that tVNS enhances action control performance.

Effects of transcranial direct current stimulation for treating depression: A modeling study

BACKGROUND

Transcranial direct current stimulation (tDCS) above the left dorsolateral prefrontal cortex (lDLPFC) has been widely used to improve symptoms of major depressive disorder (MDD). However, the effects of different stimulation protocols in the entire frontal lobe have not been investigated in a large sample including patient data.

METHODS

We used 38 head models created from structural magnetic resonance imaging data of 19 healthy adults and 19 MDD patients and applied computational modeling to simulate the spatial distribution of tDCS-induced electric fields (EFs) in 20 frontal regions. We evaluated effects of seven bipolar and two multi-electrode 4 × 1 tDCS protocols.

RESULTS

For bipolar montages, EFs were of comparable strength in the lDLPFC and in the medial prefrontal cortex (MPFC). Depending on stimulation parameters, EF cortical maps varied to a considerable degree, but were found to be similar in controls and patients. 4 × 1 montages produced more localized, albeit weaker effects.

LIMITATIONS

White matter anisotropy was not modeled. The relationship between EF strength and clinical response to tDCS could not be evaluated.

CONCLUSIONS

In addition to lDLPFC stimulation, excitability changes in the MPFC should also be considered as a potential mechanism underlying clinical efficacy of bipolar montages. MDD-associated anatomical variations are not likely to substantially influence current flow. Individual modeling of tDCS protocols can substantially improve cortical targeting. We make recommendations for future research to explicitly test the contribution of lDLPFC vs. MPFC stimulation to therapeutic outcomes of tDCS in this disorder.

Individual Differences in Uncertainty Tolerance Are not Associated With Cognitive Control Functions in the Flanker Task

Abstract. Cognitive control refers to the ability to make correct decisions concurrent to distracting information, and to adapt to conflicting stimulus configurations, eventually promoting goal-directed behavior. Previous research has linked individual differences in cognitive control to psychopathological conditions such as anxiety. However, a link with uncertainty tolerance (UT) has not been tested so far, although both constructs describe cognitive and behavioral performance in ambiguous situations, thus they share some similarities. We probed cognitive control in web-based experimentation (jsPsych) with a simple flanker task (N = 111) and a version without confounds in episodic memory (N = 116). Both experiments revealed two well-established behavioral indices: congruency effects (CEs) and congruency-sequence effects (CSEs). Only small-to-zero correlations emerged between CEs, UT, and need for cognitive closure (NCC), a personality trait inversely related to UT. A subtle correlation (r = .18) was noted in Experiment 2 between NCC and CSE. Throughout, Bayesian analyses provided anecdotal-to-moderate evidence for the null-hypotheses.

Prefrontal transcranial direct current stimulation (tDCS) as treatment for major depression: study design and methodology of a multicenter triple blind randomized placebo controlled trial (DepressionDC)

Transcranial direct current stimulation (tDCS) has been proposed as novel treatment for major depressive disorder (MDD) based on clinical pilot studies as well as randomized controlled monocentric trials. The DepressionDC trial is a triple-blind (blinding of rater, operator and patient), randomized, placebo controlled multicenter trial investigating the efficacy and safety of prefrontal tDCS used as additive treatment in MDD patients who have not responded to selective serotonin reuptake inhibitors (SSRI). At 5 study sites, 152 patients with MDD receive a 6-weeks treatment with active tDCS (anode F3 and cathode F4, 2 mA intensity, 30 min/day) or sham tDCS add-on to a stable antidepressant medication with an SSRI. Follow-up visits are at 3 and 6 months after the last tDCS session. The primary outcome measure is the change of the Montgomery-Asberg Depression Rating Scale (MADRS) scores at week 6 post-randomisation compared to baseline. Secondary endpoints also cover other psychopathological domains, and a comprehensive safety assessment includes measures of cognition. Patients undergo optional investigations comprising genetic testing and functional magnetic resonance imaging (fMRI) of structural and functional connectivity. The study uses also an advanced tDCS technology including standard electrode positioning and recording of technical parameters (current, impedance, voltage) in every tDCS session. Aside reporting the study protocol here, we present a novel approach for monitoring technical parameters of tDCS which will allow quality control of stimulation and further analysis of the interaction between technical parameters and clinical outcome. The DepressionDC trial will hopefully answer the important clinical question whether prefrontal tDCS is a safe and effective antidepressant intervention in patients who have not sufficiently responded to SSRIs.

TRIAL REGISTRY

ClinicalTrials.gov Identifier NCT0253016.

Single-session transcranial direct current stimulation induces enduring enhancement of visual processing speed in patients with major depression

Attentional deficits are considered key cognitive symptoms in major depressive disorder (MDD) arising from abnormal activation patterns within dorsolateral prefrontal cortex (dlPFC) alertness networks. Altering these activity patterns with transcranial direct current stimulation (tDCS) might thus ameliorate alertness-dependent cognitive deficits in MDD patients. In a double-blind, randomized, sham-controlled study, we investigated the effect of a single session of anodal tDCS (2 mA) applied to the left dlPFC on different parameters of visual attention based on Bundesen's theory of visual attention (Psychol Rev 97(4):523-547, 1990) in a group of 20 patients with MDD and a control group of 20 healthy participants. The parametric attention assessment took place before, immediately after and 24 h after tDCS intervention. It revealed a selective impairment in visual processing speed as a primary functional deficit in MDD at baseline assessment. Furthermore, a significant stimulation condition × time point interaction showed that verum tDCS over the left dlPFC resulted in a processing speed enhancement 24 h post-stimulation in MDD patients. In healthy control participants, we did not find similar tDCS-induced effects. Our results suggest that even a single session of tDCS over the dlPFC can induce enduring neurocognitive benefits that indicate an amelioration of cortical under-arousal in MDD patients in a time frame beyond that of immediate, excitability increases that are directly induced by the current.

Augmentation of working memory training by transcranial direct current stimulation (tDCS)

Transcranial direct current stimulation (tDCS) to the dorsolateral prefrontal cortex (dlPFC) can modulate working memory (WM) performance. However, evidence regarding the enhancement of WM training, its sustainability and transferability is ambiguous. Since WM functioning appears to be lateralized in respect to stimulus characteristics, this study examined the difference between task-congruent (spatial-right, verbal-left), task-incongruent (spatial-left, verbal-right) and sham tDCS in regards to the efficacy of WM training. In a randomized, sham-controlled experiment, 71 healthy adults trained on a spatial or verbal adaptive n-back task. After a baseline session, anodal or sham tDCS (1 mA) to the right or left dlPFC was applied during the next three training sessions. Sustainability of training gains and near-transfer (verbal or spatial 3-back task) were tested in a fourth training and a follow-up session. Compared to sham stimulation, we found a steeper learning curve when WM training was combined with task-congruent tDCS. This advantage was also present compared to task-incongruent tDCS. Moreover, these effects lasted for up to nine months and transferred to the respective untrained task. These long-lasting, transferable, task-specific effects demonstrate a behaviorally relevant and sustainable facilitation of neuroplastic processes by tDCS that could be harnessed for the treatment of disorders associated with deficient WM.

[The German research network for mental disorders]

Mental disorders are among the greatest medical and social challenges facing us. They can occur at all stages of life and are among the most important commonly occurring diseases. In Germany 28 % of the population suffer from a mental disorder every year, while the lifetime risk of suffering from a mental disorder is almost 50 %. Mental disorders cause great suffering for those affected and their social network. Quantitatively speaking, they can be considered to be among those diseases creating the greatest burden for society due to reduced productivity, absence from work and premature retirement. The Federal Ministry of Education and Research is funding a new research network from 2015 to 2019 with up to 35 million euros to investigate mental disorders in order to devise and develop better therapeutic measures and strategies for this population by means of basic and translational clinical research. This is the result of a competitive call for research proposals entitled research network for mental diseases. It is a nationwide network of nine consortia with up to ten psychiatric and clinical psychology partner institutions from largely university-based research facilities for adults and/or children and adolescents. Furthermore, three cross-consortia platform projects will seek to identify shared causes of diseases and new diagnostic modalities for anxiety disorders, attention deficit hyperactivity disorders (ADHS), autism, bipolar disorders, depression, schizophrenia and psychotic disorders as well as substance-related and addictive disorders. The spectrum of therapeutic approaches to be examined ranges from innovative pharmacological and psychotherapeutic treatment to novel brain stimulation procedures. In light of the enormous burden such diseases represent for society as a whole, a sustainable improvement in the financial support for those researching mental disorders seems essential. This network aims to become a nucleus for long overdue and sustained support for a German center for mental disorders.