Treatment of depression with transcranial direct current stimulation (tDCS): A Review

An Investigation of Parameter-Dependent Cell-Type Specific Effects of Transcranial Focused Ultrasound Stimulation Using an Awake Head-Fixed Rodent Model

Transcranial focused ultrasound (tFUS) is a promising neuromodulation technique able to target shallow and deep brain structures with high precision. Previous studies have demonstrated that tFUS stimulation responses are both cell-type specific and controllable through altering stimulation parameters. Specifically, tFUS can elicit time-locked neural activity in regular spiking units (RSUs) that is sensitive to increases in pulse repetition frequency (PRF), while time-locked responses are not seen in fast spiking units (FSUs). These findings suggest a unique capability of tFUS to alter circuit network dynamics with cell-type specificity; however, these results could be biased by the use of anesthesia, which significantly modulates neural activities. In this study, we develop an awake head-fixed rat model specifically designed for tFUS study, and address a key question if tFUS still has cell-type specificity under awake conditions. Using this novel animal model, we examined a series of PRFs and burst duty cycles (DCs) to determine their effects on neuronal subpopulations without anesthesia. We conclude that cell-type specific time-locked and delayed responses to tFUS as well as PRF and DC sensitivity are present in the awake animal model and that despite some differences in response, isoflurane anesthesia is not a major confound in studying the cell-type specificity of ultrasound neuromodulation. We further determine that, in an awake, head-fixed setting, the preferred PRF and DC for inducing time-locked excitation with our pulsed tFUS paradigm are 1500 Hz and 60%, respectively.

Spatiotemporal Distributions of Acoustic Propagation in Skull During Ultrasound Neuromodulation

There is widespread interest and concern about the evidence and hypothesis that the auditory system is involved in ultrasound neuromodulation. We have addressed this problem by performing acoustic shear wave simulations in mouse skull and behavioral experiments in deaf mice. The simulation results showed that shear waves propagating along the skull did not reach sufficient acoustic pressure in the auditory cortex to modulate neurons. Behavioral experiments were subsequently performed to awaken anesthetized mice with ultrasound targeting the motor cortex or ventral tegmental area (VTA). The experimental results showed that ultrasound stimulation (US) of the target areas significantly increased arousal scores even in deaf mice, whereas the loss of ultrasound gel abolished the effect. Immunofluorescence staining also showed that ultrasound can modulate neurons in the target area, whereas neurons in the auditory cortex required the involvement of the normal auditory system for activation. In summary, the shear waves propagating along the skull cannot reach the auditory cortex and induce neuronal activation. Ultrasound neuromodulation-induced arousal behavior needs direct action on functionally relevant stimulation targets in the absence of auditory system participation.

The Application of tDCS to Treat Pain and Psychocognitive Symptoms in Cancer Patients: A Scoping Review

Background

The use of transcranial direct current stimulation (tDCS) to modulate pain, psychological aspects, and cognitive functions has increased in recent years. The present scoping review aims to investigate the use of tDCS in cancer patients and its significant impact on psychocognitive and pain related symptoms.

Methods

From the earliest available date to June 2023, a comprehensive search was conducted in three electronic scientific databases-PubMed, Scopus, and Embase-and other supplementary sources. Ten relevant studies were identified and included, comprising single case studies, randomized controlled trials, pilot studies, and one retrospective study. PRISMA guidelines for scoping reviews were followed.

Results

These studies investigated the use of tDCS to improve pain and psychocognitive aspects in patients with various types of cancer, including breast, oral, bladder, lung, pancreatic, head and neck cancer, hepatocellular carcinoma, and meningioma. Overall, the results suggest that tDCS has shown efficacy in relieving pain, reducing anxiety and depression, and improving cognitive function in cancer patients.

Conclusion

Due to the limited number and high heterogeneity of the existing literature in this field, more investigation and the establishment of standardized protocols would be required to obtain more conclusive evidence.

Individual and group-level optimization of electric field in deep brain region during multichannel transcranial electrical stimulation

Electrode montage optimization for transcranial electric stimulation (tES) is a challenging topic for targeting a specific brain region. Targeting the deep brain region is difficult due to tissue inhomogeneity, resulting in complex current flow. In this study, a simplified protocol for montage optimization is proposed for multichannel tES (mc-tES). The purpose of this study was to reduce the computational cost for mc-tES optimization and to evaluate the mc-tES for deep brain regions. Optimization was performed using a simplified protocol for montages under safety constraints with 20 anatomical head models. The optimization procedure is simplified using the surface EF of the deep brain target region, considering its small volume and non-concentric distribution of the electrodes. Our proposal demonstrated that the computational cost was reduced by >90%. A total of six-ten electrodes were necessary for robust EF in the target region. The optimization with surface EF is comparable to or marginally better than using conventional volumetric EF for deep brain tissues. An electrode montage with a mean injection current amplitude derived from individual analysis was demonstrated to be useful for targeting the deep region at the group level. The optimized montage and injection current were derived at the group level. Our proposal at individual and group levels showed great potential for clinical application.

Ultrasound neuromodulation of cultured hippocampal neurons

Ultrasound is becoming an emerging and promising method for neuromodulation due to its advantage of noninvasiveness and its high spatial resolution. However, the underlying principles of ultrasound neuromodulation have not yet been elucidated. We have herein developed a new in vitro setup to study the ultrasonic neuromodulation, and examined various parameters of ultrasound to verify the effective conditions to evoke the neural activity. Neurons were stimulated with 0.5 MHz center frequency ultrasound, and the action potentials were recorded from rat hippocampal neural cells cultured on microelectrode arrays. As the intensity of ultrasound increased, the neuronal activity also increased. There was a notable and significant increase in both the spike rate and the number of bursts at 50% duty cycle, 1 kHz pulse repetition frequency, and the acoustic intensities of 7.6 W/cm2 and 3.8 W/cm2 in terms of spatial-peak pulse-average intensity and spatial-peak temporal-average intensity, respectively. In addition, the impact of ultrasonic neuromodulation was assessed in the presence of a gamma-aminobutyric acid A (GABAA) receptor antagonist to exclude the effect of activated inhibitory neurons. Interestingly, it is noteworthy that the predominant neuromodulatory effects of ultrasound disappeared when the GABAA blocker was introduced, suggesting the potential of ultrasonic stimulation specifically targeting inhibitory neurons. The experimental setup proposed herein could serve as a useful tool for the clarification of the mechanisms underlying the electrophysiological effects of ultrasound.

Brain stimulation-on-a-chip: a neuromodulation platform for brain slices

Electrical stimulation of ex vivo brain tissue slices has been a method used to understand mechanisms imparted by transcranial direct current stimulation (tDCS), but there are significant direct current electric field (dcEF) dosage and electrochemical by-product concerns in conventional experimental setups that may impact translational findings. Therefore, we developed an on-chip platform with fluidic, electrochemical, and magnetically-induced spatial control. Fluidically, the chamber geometrically confines precise dcEF delivery to the enclosed brain slice and allows for tissue recovery in order to monitor post-stimulation effects. Electrochemically, conducting hydrogel electrodes mitigate stimulation-induced faradaic reactions typical of commonly-used metal electrodes. Magnetically, we applied ferromagnetic substrates beneath the tissue and used an external permanent magnet to enable in situ rotational control in relation to the dcEF. By combining the microfluidic chamber with live-cell calcium imaging and electrophysiological recordings, we showcased the potential to study the acute and lasting effects of dcEFs with the potential of providing multi-session stimulation. This on-chip bioelectronic platform presents a modernized yet simple solution to electrically stimulate explanted tissue by offering more environmental control to users, which unlocks new opportunities to conduct thorough brain stimulation mechanistic investigations.

Volumetric measurements of weak current-induced magnetic fields in the human brain at high resolution

PURPOSE

Clinical use of transcranial electrical stimulation (TES) requires accurate knowledge of the injected current distribution in the brain. MR current density imaging (MRCDI) uses measurements of the TES-induced magnetic fields to provide this information. However, sufficient sensitivity and image quality in humans in vivo has only been documented for single-slice imaging.

METHODS

A recently developed, optimally spoiled, acquisition-weighted, gradient echo-based 2D-MRCDI method has now been advanced for volume coverage with densely or sparsely distributed slices: The 3D rectilinear sampling (3D-DENSE) and simultaneous multislice acquisition (SMS-SPARSE) were optimized and verified by cable-loop experiments and tested with 1-mA TES experiments for two common electrode montages.

RESULTS

Comparisons between the volumetric methods against the 2D-MRCDI showed that relatively long acquisition times of 3D-DENSE using a single slab with six slices hindered the expected sensitivity improvement in the current-induced field measurements but improved sensitivity by 61% in the Laplacian of the field, on which some MRCDI reconstruction methods rely. Also, SMS-SPARSE acquisition of three slices, with a factor 2 CAIPIRINHA (controlled aliasing in parallel imaging results in higher acceleration) acceleration, performed best against the 2D-MRCDI with sensitivity improvements for the∆ B z , c $$ \Delta {B}_{z,c} $$ and Laplacian noise floors of 56% and 78% (baseline without current flow) as well as 43% and 55% (current injection into head). SMS-SPARSE reached a sensitivity of 67 pT for three distant slices at 2 × 2 × 3 mm3 resolution in 10 min of total scan time, and consistently improved image quality.

CONCLUSION

Volumetric MRCDI measurements with high sensitivity and image quality are well suited to characterize the TES field distribution in the human brain.

Multi-scale model of axonal and dendritic polarization by transcranial direct current stimulation in realistic head geometry

BACKGROUND

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation modality that can alter cortical excitability. However, it remains unclear how the subcellular elements of different neuron types are polarized by specific electric field (E-field) distributions.

OBJECTIVE

To quantify neuronal polarization generated by tDCS in a multi-scale computational model.

METHODS

We embedded layer-specific, morphologically-realistic cortical neuron models in a finite element model of the E-field in a human head and simulated steady-state polarization generated by conventional primary-motor-cortex-supraorbital (M1-SO) and 4 × 1 high-definition (HD) tDCS. We quantified somatic, axonal, and dendritic polarization of excitatory pyramidal cells in layers 2/3, 5, and 6, as well as inhibitory interneurons in layers 1 and 4 of the hand knob.

RESULTS

Axonal and dendritic terminals were polarized more than the soma in all neurons, with peak axonal and dendritic polarization of 0.92 mV and 0.21 mV, respectively, compared to peak somatic polarization of 0.07 mV for 1.8 mA M1-SO stimulation. Both montages generated regions of depolarization and hyperpolarization beneath the M1 anode; M1-SO produced slightly stronger, more diffuse polarization peaking in the central sulcus, while 4 × 1 HD produced higher peak polarization in the gyral crown. The E-field component normal to the cortical surface correlated strongly with pyramidal neuron somatic polarization (R2>0.9), but exhibited weaker correlations with peak pyramidal axonal and dendritic polarization (R2:0.5-0.9) and peak polarization in all subcellular regions of interneurons (R2:0.3-0.6). Simulating polarization by uniform local E-field extracted at the soma approximated the spatial distribution of tDCS polarization but produced large errors in some regions (median absolute percent error: 7.9 %).

CONCLUSIONS

Polarization of pre- and postsynaptic compartments of excitatory and inhibitory cortical neurons may play a significant role in tDCS neuromodulation. These effects cannot be predicted from the E-field distribution alone but rather require calculation of the neuronal response.

No effect of prefrontal transcranial direct current stimulation (tDCS) on food craving, food reward and subjective appetite in females displaying mild-to-moderate binge-type behaviour

Previous work suggests there may be an effect of transcranial direct current stimulation (tDCS) on appetite control in people at risk of overconsumption, however findings are inconsistent. This study aimed to further understand the potential eating behaviour trait-dependent effect of tDCS, specifically in those with binge-type behaviour. Seventeen females (23 ± 7 years, 25.4 ± 3.8 kg m-2) with mild-to-moderate binge eating behaviour completed two sessions of double-blind, randomised and counterbalanced anodal and sham tDCS applied over the right dorsolateral prefrontal cortex at 2.0 mA for 20 min. Subjective appetite visual analogue scales (VAS), the Food Craving Questionnaire-State (FCQ-S), and Leeds Food Preference Questionnaire (LFPQ) were completed pre- and post-tDCS. Participants then consumed a fixed-energy meal, followed by the VAS, FCQ-S and LFPQ. No difference between pre- and post-tDCS scores were found across fullness (p = 0.275, BF10 = 0.040), prospective consumption (p = 0.127, BF10 = 0.063), desire to eat (p = 0.247, BF10 = 0.054) or FCQ-S measures (p = 0.918, BF10 = 0.040) when comparing active and sham protocols. Only explicit liking and wanting for high-fat sweet foods were significantly different between conditions, with increased scores following active tDCS. When controlling for baseline hunger, the significant differences were removed (p = 0.138 to 0.161, BF10 = 0.810 to 1.074). The present data does not support the eating behaviour trait dependency of tDCS in a specific cohort of female participants with mild-to-moderate binge eating scores, and results align with those from individuals with healthy trait scores. This suggests participants with sub-clinical binge eating behaviour do not respond to tDCS. Future work should further explore effects in clinical and sub-clinical populations displaying susceptibility to overconsumption and weight gain.

Multi-scale model of axonal and dendritic polarization by transcranial direct current stimulation in realistic head geometry

Background

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation modality that can alter cortical excitability. However, it remains unclear how the subcellular elements of different neuron types are polarized by specific electric field (E-field) distributions.

Objective

To quantify neuronal polarization generated by tDCS in a multi-scale computational model.

Methods

We embedded layer-specific, morphologically-realistic cortical neuron models in a finite element model of the E-field in a human head and simulated steady-state polarization generated by conventional primary-motor-cortex-supraorbital (M1-SO) and 4×1 high-definition (HD) tDCS. We quantified somatic, axonal, and dendritic polarization of excitatory pyramidal cells in layers 2/3, 5, and 6, as well as inhibitory interneurons in layers 1 and 4 of the hand knob.

Results

Axonal and dendritic terminals were polarized more than the soma in all neurons, with peak axonal and dendritic polarization of 0.92 mV and 0.21 mV, respectively, compared to peak somatic polarization of 0.07 mV for 1.8 mA M1-SO stimulation. Both montages generated regions of depolarization and hyperpolarization beneath the M1 anode; M1-SO produced slightly stronger, more diffuse polarization peaking in the central sulcus, while 4×1 HD produced higher peak polarization in the gyral crown. Simulating polarization by uniform local E-field approximated the spatial distribution of tDCS polarization but produced large errors in some regions.

Conclusions

Polarization of pre- and postsynaptic compartments of excitatory and inhibitory cortical neurons may play a significant role in tDCS neuromodulation. These effects cannot be predicted from the E-field distribution alone but rather require calculation of the neuronal response.

Noninvasive Neuromodulation in Parkinson's Disease: Insights from Animal Models

The mainstay treatments for Parkinson's Disease (PD) have been limited to pharmacotherapy and deep brain stimulation. While these interventions are helpful, a new wave of research is investigating noninvasive neuromodulation methods as potential treatments. Some promising avenues have included transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), electroconvulsive therapy (ECT), and focused ultrasound (FUS). While these methods are being tested in PD patients, investigations in animal models of PD have sought to elucidate their therapeutic mechanisms. In this rapid review, we assess the available animal literature on these noninvasive techniques and discuss the possible mechanisms mediating their therapeutic effects based on these findings.

Dual-hemisphere anodal transcranial direct current stimulation improves bilateral motor synergies

Transcranial direct current stimulation (tDCS) is one of the non-invasive brain stimulation techniques that can improve motor functions. As bimanual motor actions require high motor cortical activations between hemispheres, applying bilateral anodal stimulation on left and right sides of primary motor cortex (M1) can improve for improvements in bimanual motor tasks. This study investigated which bilateral tDCS protocol effectively improves bimanual hand-grip force control capabilities in healthy young adults. We used three different bilateral tDCS protocols: (a) dual-anodal stimulation on the M1 of bilateral hemispheres (Bi-AA), (b) anodal-cathodal stimulation on the M1 of dominant and nondominant hemispheres (Bi-AC), and (c) sham stimulation (Sham). The results indicated that applying the Bi-AA significantly improved bilateral motor synergies estimated by uncontrolled manifold analysis relative to Sham. However, these differences were not observed in the comparison between Bi-AA and Bi-AC as well as between Bi-AC and Sham. These findings suggest that facilitating motor cortical activations between both hemispheres may be an additional option for advancing interlimb motor coordination patterns.

Non-pharmacological treatment-related changes of molecular biomarkers in major depressive disorder: A systematic review and meta-analysis

Background

Major depressive disorder (MDD) is a serious mood disorder and leading cause of disability. Despite treatment advances, approximately 30% of individuals with MDD do not achieve adequate clinical response. Better understanding the biological mechanism(s) underlying clinical response to specific psychopharmacological interventions may help fine tune treatments in order to further modulate their underlying mechanisms of action. However, little is known regarding the effect of non-pharmacological treatments (NPTs) on candidate molecular biomarker levels in MDD. This review aims to identify molecular biomarkers that may elucidate NPT response for MDD.

Methods

We performed a systematic review and a multilevel linear mixed-effects meta-analyses, and a meta-regression. Searches were performed in PubMed, Scopus, and PsycINFO in October 2020 and July 2021.

Results

From 1387 retrieved articles, 17 and six studies were included in the systematic review and meta-analyses, respectively. Although there was little consensus associating molecular biomarker levels with symptomology and/or treatment response, brain metabolites accessed via molecular biomarker-focused neuroimaging techniques may provide promising information on whether an individual with MDD would respond positively to NPTs. Furthermore, non-invasive brain stimulation interventions significantly increased the expression of neurotrophic factors (NTFs) compared to sham/placebo, regardless of add-on pharmacological treatment.

Conclusions

NTFs are candidate biomarkers to fine-tune NIBS for MDD treatment.

Effect of citicoline and transcranial direct current stimulation on depressive-like behaviors in mice & quot

Recent investigations revealed the positive role of transcranial direct current stimulation (tDCS) in the treatment of depressive-like behavior & quot. Citicoline is a dietary supplement. It acts as a neuroprotective factor for the treatment of neurological disorders. The aim of this research was to evaluate a possible interaction between tDCS and citicoline on the modulation of depressive-like behavior s & quot in male mice. For tDCS, an electrode was surgically implanted in the left prefrontal of the brain of male mice & quot. Acute restraint stress was induced by movement restraint for 4h. Locomotor activity and depressive-like behaviors & quot were examined by open field test (OFT), forced swimming test (FST), and tail suspension test (TST). The results indicated that the intraperitoneal (i.p.) administration of citicoline, left prefrontal anodal tDCS, and co-treatment of citicoline and tDCS had no significant effect on locomotor activity. I.p. injection of citicoline (30mg/kg) decreased immobility time in the FST and TST, showing an antidepressant-like effect & quot. Moreover, the application of left prefrontal anodal tDCS (0.2mA) for 20min induced antidepressant-like effect & quot by reducing immobility time in the FST and TST. Co-administration of citicoline (7 and 15mg/kg) along with tDCS (0.1mA) decreased immobility time in the FST and TST, indicating an antidepressant-like effect & quot. Therefore, it can be concluded that administration of citicoline in combination with tDCS enhanced the efficacy of tDCS for remedy of depressive-like behaviors & quot.

Exploring the Potential of Transcranial Direct Current Stimulation for Relieving Central Post-Stroke Pain: A Randomized Controlled Pilot Study

The potential of transcranial direct current stimulation (tDCS) as a non-invasive brain stimulation technique for treating pain has been studied. However, its effectiveness in patients with central post-stroke pain (CPSP) and the impact of lesion location remain unclear. This study investigated tDCS's pain reduction effects in patients with CPSP. Twenty-two patients with CPSP were randomized into the tDCS or sham groups. The tDCS group received stimulation of the primary motor cortex (M1) for 20 min, five times weekly, for two weeks, and underwent evaluations at baseline, immediately after the intervention, and one week after the intervention. The tDCS group had no significant improvement compared to the sham group in pain, depression, and quality of life. Nevertheless, significant changes were identified within the tDCS group, and the pain trends appeared to be influenced by the lesion location. These findings provide important insights into the use of tDCS in patients with CPSP, which could inform further research and development of pain treatment options.

Electrochemical and electrophysiological considerations for clinical high channel count neural interfaces

Electrophysiological recording and stimulation are the gold standard for functional mapping during surgical and therapeutic interventions as well as capturing cellular activity in the intact human brain. A critical component probing human brain activity is the interface material at the electrode contact that electrochemically transduces brain signals to and from free charge carriers in the measurement system. Here, we summarize state-of-the-art electrode array systems in the context of translation for use in recording and stimulating human brain activity. We leverage parametric studies with multiple electrode materials to shed light on the varied levels of suitability to enable high signal-to-noise electrophysiological recordings as well as safe electrophysiological stimulation delivery. We discuss the effects of electrode scaling for recording and stimulation in pursuit of high spatial resolution, channel count electrode interfaces, delineating the electrode-tissue circuit components that dictate the electrode performance. Finally, we summarize recent efforts in the connectorization and packaging for high channel count electrode arrays and provide a brief account of efforts toward wireless neuronal monitoring systems.

Repetitive transcranial magnetic stimulation (rTMS) triggers dose-dependent homeostatic rewiring in recurrent neuronal networks

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation technique used to induce neuronal plasticity in healthy individuals and patients. Designing effective and reproducible rTMS protocols poses a major challenge in the field as the underlying biomechanisms remain elusive. Current clinical protocol designs are often based on studies reporting rTMS-induced long-term potentiation or depression of synaptic transmission. Herein, we employed computational modeling to explore the effects of rTMS on long-term structural plasticity and changes in network connectivity. We simulated a recurrent neuronal network with homeostatic structural plasticity between excitatory neurons, and demonstrated that this mechanism was sensitive to specific parameters of the stimulation protocol (i.e., frequency, intensity, and duration of stimulation). The feedback-inhibition initiated by network stimulation influenced the net stimulation outcome and hindered the rTMS-induced homeostatic structural plasticity, highlighting the role of inhibitory networks. These findings suggest a novel mechanism for the lasting effects of rTMS, i.e., rTMS-induced homeostatic structural plasticity, and highlight the importance of network inhibition in careful protocol design, standardization, and optimization of stimulation.

Reviving the Dynamics of Attacked Reservoir Computers

Physically implemented neural networks are subject to external perturbations and internal variations. Existing works focus on the adversarial attacks but seldom consider attack on the network structure and the corresponding recovery method. Inspired by the biological neural compensation mechanism and the neuromodulation technique in clinical practice, we propose a novel framework of reviving attacked reservoir computers, consisting of several strategies direct at different types of attacks on structure by adjusting only a minor fraction of edges in the reservoir. Numerical experiments demonstrate the efficacy and broad applicability of the framework and reveal inspiring insights into the mechanisms. This work provides a vehicle to improve the robustness of reservoir computers and can be generalized to broader types of neural networks.

Electroceutical and Bioelectric Therapy: Its Advantages and Limitations

Given the long history, the field of electroceutical and bioelectric therapy has grown impressively, recognized as the main modality of mental health treatments along with psychotherapy and pharmacotherapy. Electroceutical and bioelectric therapy comprises electroconvulsive therapy (ECT), vagus nerve stimulation (VNS), repetitive transcranial magnetic stimulation (rTMS), deep brain stimulation (DBS), transcranial electrical stimulation (tES), and other brain stimulation techniques. Much empirical research has been published regarding the application guidelines, mechanism of action, and efficacy of respective brain stimulation techniques, but no comparative study that delineates the advantages and limitations of each therapy exists for a comprehensive understanding of each technique. This review provides a comparison of existing electroceutical and bioelectric techniques, primarily focusing on the therapeutic advantages and limitations of each therapy in the current electroceutical and bioelectric field.

Neuromodulatory effects of transcranial electrical stimulation on emotion regulation in internalizing psychopathologies

OBJECTIVE

We hypothesize offset theta-tACS (transcranial alternating current stimulation) improves emotion regulation (ER) and psychopathology more than transcranial direct current stimulation (tDCS) in participants with internalizing psychopathologies (IPs).

METHODS

This pilot study utilized a double-blind, pseudo-counterbalanced, sham-controlled design with participants with IPs. Participants were assigned to receive tDCS or tACS, underwent four stimulation sessions (two sham), and completed an emotion regulation task (ERT) during or after stimulation. Participants completed the Beck Depression Inventory before/after the study, the Spielberger State and Trait Anxiety Index after each ERT, and rated their arousal, valence, and perceived reappraisal ability during the ERT.

RESULTS

Participants receiving either stimulation type showed a reduction in anxiety, depression, and valence and arousal ratings. We additionally discovered an effect demonstrating those who received sham stimulation first displayed little-to-no change in any score across the study, but tACS participants who received verum stimulation first showed significant improvements in each metric.

CONCLUSIONS

Improving ER capabilities via theta tACS has the potential to yield beneficial clinical effects.

SIGNIFICANCE

This study adds validity to the use of non-invasive neuromodulatory methods, especially tACS, to alleviate IPs. Additional research is needed to better understand the effects of sham stimulation. Careful consideration of sham incorporation should be made in future studies.

Treatment efficacy of tDCS and predictors of treatment response in patients with post-traumatic stress disorder

BACKGROUND

Although transcranial direct stimulation (tDCS) has been proposed as an alternative treatment option for various psychiatric disorders, there is inconsistent information regarding the treatment effects of tDCS for patients with post-traumatic stress disorder (PTSD). This study aimed to investigate the tDCS efficacy and identify predictors of treatment response to tDCS in patients with PTSD.

METHOD

Fifty-one patients received 10 sessions of tDCS involving the position of the anode over the F3 area and cathode over the F4 as a condition of 2.0 mA and 20 min duration. Digit span test and 10 questionnaires (Clinician-Administered PTSD Scale (CAPS), Cognitive Emotion Regulation Questionnaire (CERQ), Multidimensional Experiential Avoidance Questionnaire (MEAQ), etc.) were used to measure tDCS effects on PTSD symptoms and identify predictors of response to tDCS.

RESULTS

1) 50.9 % of patients had a significant reduction in the frequency and severity of PTSD symptoms, 2) PTSD-related symptoms such as depression, anxiety, rumination, and quality of life were significantly improved, 3) baseline scores on rumination and digit span test significantly predicted treatment response to tDCS.

LIMITATIONS

This study was open design without a sham control group. Also, the patients' medications were not controlled.

CONCLUSION

This study highlighted the efficacy of frontal tDCS for the treatment of patients with PTSD and identified rumination and digit span as favorable predictive factors for the outcomes of tDCS.

L1-norm vs. L2-norm fitting in optimizing focal multi-channel tES stimulation: linear and semidefinite programming vs. weighted least squares

BACKGROUND AND OBJECTIVE

This study focuses on Multi-Channel Transcranial Electrical Stimulation, a non-invasive brain method for stimulating neuronal activity under the influence of low-intensity currents. We introduce a mathematical formulation for finding a current pattern that optimizes an L1-norm fit between a given focal target distribution and volumetric current density inside the brain. L1-norm is well-known to favor well-localized or sparse distributions compared to L2-norm (least-squares) fitted estimates.

METHODS

We present a linear programming approach that performs L1-norm fitting and penalization of the current pattern (L1L1) to control the number of non-zero currents. The optimizer filters a large set of candidate solutions using a two-stage metaheuristic search from a pre-filtered set of candidates.

RESULTS

The numerical simulation results obtained with both 8- and 20-channel electrode montages suggest that our hypothesis on the benefits of L1-norm data fitting is valid. Compared to an L1-norm regularized L2-norm fitting (L1L2) via semidefinite programming and weighted Tikhonov least-squares method (TLS), the L1L1 results were overall preferable for maximizing the focused current density at the target position, and the ratio between focused and nuisance current magnitudes.

CONCLUSIONS

We propose the metaheuristic L1L1 optimization approach as a potential technique to obtain a well-localized stimulus with a controllable magnitude at a given target position. L1L1 finds a current pattern with a steep contrast between the anodal and cathodal electrodes while suppressing the nuisance currents in the brain, hence, providing a potential alternative to modulate the effects of the stimulation, e.g., the sensation experienced by the subject.

Combination effects of mesenchymal stem cells transplantation and anodal transcranial direct current stimulation on a cuprizone-induced mouse model of multiple sclerosis

Multiple sclerosis (MS) has no absolute treatment, and researchers are still exploring to introduce promising therapy for MS. Transcranial direct current stimulation (tDCS), is a safe, non-invasive procedure for brain stimulating which can enhance working memory, cognitive neurohabitation and motor recovery. Here, we evaluated the effects of tDCS treatment and Mesenchymal stem cells (MSCs) transplantation on remyelination ability of a Cuprizone (CPZ)-induced demyelination mouse model. tDCS significantly increased the motor coordination and balance abilities in CPZ + tDCS and CPZ + tDCS + MSCs mice in comparison to the CPZ mice. Luxol fast blue (LFB) staining showed that tDCS and MSCs transplantation could increase remyelination capacity in CPZ + tDCS and CPZ + MSCs mice compared to the CPZ mice. But, the effect of tDCS with MSCs transplantation on remyelination process was larger than each of treatment alone. Immunofluorescence technique indicated that the numbers of Olig2⁺ cells were increased by tDCS and MSCs transplantation in CPZ + tDCS and CPZ + MSCs mice compared to the CPZ mice. Interestingly, the combination effect of tDCS and MSCs was larger than each of treatment alone on Oligodendrocytes population. MSCs transplantation significantly decreased the TUNEL⁺ cells in CPZ + MSCs and CPZ + tDCS + MSCs mice in comparison to the CPZ mice. Also, the combination effects of tDCS and MSCs transplantation was much larger than each of treatment alone on increasing the mRNA expression of BDNF and Sox2, while decreasing P53 as compared to CPZ mice. It can be concluded that the combination usage of tDCS and MSCs transplantation enhance remyelination process in CPZ-treated mice by increasing transplanted stem cell homing, oligodendrocyte generation and decreasing apoptosis.

Non-invasive neuromodulation of dorsolateral prefrontal cortex to reduce craving in alcohol use disorder: A meta-analysis

Introduction

While several pharmacological and behavioral treatments are available for alcohol use disorder (AUD), they may not be effective for all patients. The aim of this systematic review and meta-analysis was to evaluate the efficacy and safety of rTMS and tDCS for craving in AUD.

Methods

EMBASE, Cochrane Library, PsycINFO, and PubMed databases were searched for original, peer-reviewed research articles in the English language published between January 2000 and January 2022. Randomized controlled trials (RCTs) reporting changes in alcohol craving among patients with AUD were selected. Random-effects meta-analysis was employed to pool data.

Results

Changes in alcohol craving were extracted from 15 RCTs. Six studies assessed the efficacy of rTMS while nine studies examined tDCS. Results demonstrated that in comparison to sham stimulation, active rTMS to the DLPFC yields small but significant reductions in alcohol craving (standardized mean difference [SMD] = -0.27, p = .03). However, DLPFC stimulation via tDCS was not superior to sham stimulation in producing changes in alcohol craving (SMD = -0.08, p = .59).

Conclusions

Our meta-analysis suggests that rTMS may be superior to tDCS in reducing alcohol craving in patients with AUD. However, additional research is needed to identify optimal stimulation parameters for both non-invasive neuromodulatory techniques in AUD.

Efficacy of Augmentation of Cognitive Behavioral Therapy With Transcranial Direct Current Stimulation for Depression: A Randomized Clinical Trial

IMPORTANCE

Major depressive disorder (MDD) affects approximately 10% of the population globally. Approximately 20% to 30% of patients with MDD do not sufficiently respond to standard treatment. Therefore, there is a need to develop more effective treatment strategies.

OBJECTIVE

To investigate whether the efficacy of cognitive behavioral therapy (CBT) for the treatment of MDD can be enhanced by concurrent transcranial direct current stimulation (tDCS).

DESIGN, SETTING, AND PARTICIPANTS

The double-blind, placebo-controlled randomized clinical trial PsychotherapyPlus was conducted at 6 university hospitals across Germany. Enrollment took place between June 2, 2016, and March 10, 2020; follow-up was completed August 27, 2020. Adults aged 20 to 65 years with a single or recurrent depressive episode were eligible. They were either not receiving medication or were receiving a stable regimen of antidepressant medication (selective serotonin reuptake inhibitor and/or mirtazapine). A total of 148 women and men underwent randomization: 53 individuals were assigned to CBT alone (group 0), 48 to CBT plus tDCS (group 1), and 47 to CBT plus sham-tDCS (group 2).

INTERVENTIONS

Participants attended a 6-week group intervention comprising 12 sessions of CBT. If assigned, tDCS was applied simultaneously. Active tDCS included stimulation with an intensity of 2 mA for 30 minutes (anode over F3, cathode over F4).

MAIN OUTCOMES AND MEASURES

The primary outcome was the change in Montgomery-Åsberg Depression Rating Scale (MADRS) score from baseline to posttreatment in the intention-to-treat sample. Scores of 0 to 6 indicate no depression; 7 to 19, mild depression; 20 to 34, moderate depression; and 34 and higher, severe depression.

RESULTS

A total of 148 patients (89 women, 59 men; mean [SD] age, 41.1 [13.7] years; MADRS score at baseline, 23.0 [6.4]) were randomized. Of these, 126 patients (mean [SD] age, 41.5 [14.0] years; MADRS score at baseline, 23.0 [6.3]) completed the study. In each of the intervention groups, intervention was able to reduce MADRS scores by a mean of 6.5 points (95% CI, 3.82-9.14 points). The Cohen d value was -0.90 (95% CI, -1.43 to -0.50), indicating a significant effect over time. However, there was no significant effect of group and no significant interaction of group × time, indicating the estimated additive effects were not statistically significant. There were no severe adverse events throughout the whole trial, and there were no significant differences of self-reported adverse effects during and after stimulation between groups 1 and 2.

CONCLUSIONS AND RELEVANCE

Based on MADRS score changes, this trial did not indicate superior efficacy of tDCS-enhanced CBT compared with 2 CBT control conditions. The study confirmed that concurrent group CBT and tDCS is safe and feasible. However, additional research on mechanisms of neuromodulation to complement CBT and other behavioral interventions is needed.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02633449.

Using dual polarities of transcranial direct current stimulation in global cerebral ischemia and its following reperfusion period attenuates neuronal injury

Multiple neuronal injury pathways are activated during cerebral ischemia and reperfusion (I/R). This study was designed to decrease potential neuronal injuries by using both transcranial direct current stimulation (tDCS) polarities in cerebral ischemia and its following reperfusion period. Ninety rats were randomly divided into six groups. In the sham group, rats were intact. In the I/R group, global cerebral I/R was only induced. In the I/R + c-tDCS and I/R + a-tDCS groups, cathodal and anodal currents were applied, respectively. In the I/R + c/a-tDCS, cathodal current was used in the cerebral ischemia and anodal in the reperfusion. In the I/R + a/c-tDCS group, cathodal and anodal currents were applied in the I/R, respectively. Hippocampal tissue was used to determine the levels of IL-1β, TNF-α, NOS, SOD, MDA, and NMDAR. Hot plate and open field tests evaluated sensory and locomotor performances. The cerebral edema was also measured. Histological assessment was assessed by H/E and Nissl staining of the hippocampal CA1 region. All tDCS modes significantly decreased IL-1β and TNF-α levels, especially in the c/a-tDCS. All tDCS caused a significant decrease in MDA and NOS levels while increasing SOD activity compared to the I/R group, especially in the c/a-tDCS mode. In the c-tDCS and a/c-tDCS groups, the NMDAR level was significantly decreased. The c/a-tDCS group improved sensory and locomotor performances more than other groups receiving tDCS. Furthermore, the least neuronal death was observed in the c/a-tDCS mode. Using two different polarities of tDCS could induce more neuroprotective versus pathophysiological pathways in cerebral I/R, especially in c/a-tDCS mode. HIGHLIGHTS: Multiple pathways of neuronal injury are activated in cerebral ischemia and reperfusion (I/R). Using tDCS could modulate neuroinflammation and oxidative stress pathways in global cerebral I/R. Using c/a-tDCS mode during cerebral I/R causes more neuroprotective effects against neuronal injuries of cerebral I/R.

Things you wanted to know (but might have been afraid to ask) about how and why to explore and modulate brain plasticity with non-invasive neurostimulation technologies

Brain plasticity can be defined as the ability of local and extended neural systems to organize either the structure and/or the function of their connectivity patterns to better adapt to changes of our inner/outer environment and optimally respond to new challenging behavioral demands. Plasticity has been traditionally conceived as a spontaneous phenomenon naturally occurring during pre and postnatal development, tied to learning and memory processes, or enabled following neural damage and their rehabilitation. Such effects can be easily observed and measured but remain hard to harness or to tame 'at will'. Non-invasive brain stimulation (NIBS) technologies offer the possibility to engage plastic phenomena, and use this ability to characterize the relationship between brain regions, networks and their functional connectivity patterns with cognitive process or disease symptoms, to estimate cortical malleability, and ultimately contribute to neuropsychiatric therapy and rehabilitation. NIBS technologies are unique tools in the field of fundamental and clinical research in humans. Nonetheless, their abilities (and also limitations) remain rather unknown and in the hands of a small community of experts, compared to widely established methods such as functional neuroimaging (fMRI) or electrophysiology (EEG, MEG). In the current review, we first introduce the features, mechanisms of action and operational principles of the two most widely used NIBS methods, Transcranial Magnetic Stimulation (TMS) and Transcranial Current Stimulation (tCS), for exploratory or therapeutic purposes, emphasizing their bearings on neural plasticity mechanisms. In a second step, we walk the reader through two examples of recent domains explored by our team to further emphasize the potential and limitations of NIBS to either explore or improve brain function in healthy individuals and neuropsychiatric populations. A final outlook will identify a series of future topics of interest that can foster progress in the field and achieve more effective manipulation of brain plasticity and interventions to explore and improve cognition and treat the symptoms of neuropsychiatric diseases.

Stimulation Montage Achieves Balanced Focality and Intensity

Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technique to treat brain disorders by using a constant, low current to stimulate targeted cortex regions. Compared to the conventional tDCS that uses two large pad electrodes, multiple electrode tDCS has recently received more attention. It is able to achieve better stimulation performance in terms of stimulation intensity and focality. In this paper, we first establish a computational model of tDCS, and then propose a novel optimization algorithm using a regularization matrix λ to explore the balance between stimulation intensity and focality. The simulation study is designed such that the performance of state-of-the-art algorithms and the proposed algorithm can be compared via quantitative evaluation. The results show that the proposed algorithm not only achieves desired intensity, but also smaller target error and better focality. Robustness analysis indicates that the results are stable within the ranges of scalp and cerebrospinal fluid (CSF) conductivities, while the skull conductivity is most sensitive and should be carefully considered in real clinical applications.

Non-invasive Brain Stimulation for Central Neuropathic Pain

The research and clinical application of the noninvasive brain stimulation (NIBS) technique in the treatment of neuropathic pain (NP) are increasing. In this review article, we outline the effectiveness and limitations of the NIBS approach in treating common central neuropathic pain (CNP). This article summarizes the research progress of NIBS in the treatment of different CNPs and describes the effects and mechanisms of these methods on different CNPs. Repetitive transcranial magnetic stimulation (rTMS) analgesic research has been relatively mature and applied to a variety of CNP treatments. But the optimal stimulation targets, stimulation intensity, and stimulation time of transcranial direct current stimulation (tDCS) for each type of CNP are still difficult to identify. The analgesic mechanism of rTMS is similar to that of tDCS, both of which change cortical excitability and synaptic plasticity, regulate the release of related neurotransmitters and affect the structural and functional connections of brain regions associated with pain processing and regulation. Some deficiencies are found in current NIBS relevant studies, such as small sample size, difficulty to avoid placebo effect, and insufficient research on analgesia mechanism. Future research should gradually carry out large-scale, multicenter studies to test the stability and reliability of the analgesic effects of NIBS.

Omnidirectional Galvanic Vestibular Stimulation in Virtual Reality

In this paper we propose omnidirectional galvanic vestibular stimulation (GVS) to mitigate cybersickness in virtual reality applications. One of the most accepted theories indicates that Cybersickness is caused by the visually induced impression of ego motion while physically remaining at rest. As a result of this sensory mismatch, people associate negative symptoms with VR and sometimes avoid the technology altogether. To reconcile the two contradicting sensory perceptions, we investigate GVS to stimulate the vestibular canals behind our ears with low-current electrical signals that are specifically attuned to the visually displayed camera motion. We describe how to calibrate and generate the appropriate GVS signals in real-time for pre-recorded omnidirectional videos exhibiting ego-motion in all three spatial directions. For validation, we conduct an experiment presenting real-world 360° videos shot from a moving first-person perspective in a VR head-mounted display. Our findings indicate that GVS is able to significantly reduce discomfort for cybersickness-susceptible VR users, creating a deeper and more enjoyable immersive experience for many people.

Efficacy and Safety of Transcranial Direct Current Stimulation on Post-Stroke Dysphagia: A Systematic Review and Meta-Analysis

Dysphagia is one of the most common symptoms in patients after stroke onset, which has multiple unfavorable effects on quality of life and functional recovery. Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation that is widely used to improve deglutition function. Recently, some studies have confirmed that tDCS enhances deglutition function after stroke. However, the number of evaluation indexes used in those studies was small, and the number of trials included was limited. Most importantly, the optimal stimulation protocol is still uncertain and the safety of tDCS has not been reviewed. Therefore, we conducted a systematic review and meta-analysis to address these shortcomings.

METHODS

Seven databases were searched entirely, including Pubmed, Cochrane Library, Web of Science, China National Knowledge Infrastructure (CNKI), Chinese Biomedical Literature Service System (SinoMed), Wan-fang database, and the Chinese Scientific Journals Database (VIP) from inception to 31 December 2021. Two reviewers independently evaluated the eligibility of retrieved data according to the selection criteria and assessed the methodological quality of the studies using the Cochrane risk of bias tool. Outcomes, measures, and indicators used in this study included the dysphagia outcome and severity scale (DOSS), modified Mann assessment of swallowing ability (MMASA), functional oral intake scale (FOIS), functional dysphagia scale (FDS), and Kubota's water-drinking test (KWDT). Sensitivity and subgroup analyses were performed to evaluate the intervention effect more specifically.

RESULTS

Fifteen trials with a total of 787 participants (394 subjects in the tDCS groups were treated with true tDCS, and 393 subjects in the control groups were wait-listed or treated with sham tDCS) involving tDCS for dysphagia after stroke and were included in the meta-analysis. Results of this meta-analysis confirmed that tDCS had a positive effect on post-stroke dysphagia. Subgroup analyses revealed that bilateral and high-intensity stimulation with tDCS had a more significant impact on post-stroke dysphagia. Furthermore, no adverse events occurred during the application of tDCS for post-stroke dysphagia.

CONCLUSION

tDCS can promote the recovery of deglutition function in patients with dysphagia after stroke. In addition, bilateral stimulation and high-intensity stimulation may have better effects. However, the safety evidence for tDCS and post-stroke dysphagia is insufficient.

Synergistic effect of combined transcranial direct current stimulation and Matrix ‎Model on the reduction of methamphetamine craving and improvement of cognitive ‎functioning: a randomized sham-controlled study

BACKGROUND

Addiction is associated with decreased activity of the prefrontal networks, especially dorsolateral prefrontal cortex (DLPFC).

OBJECTIVE

This study examined the effectiveness of transcranial direct current stimulation (tDCS) over DLPFC in combination with Matrix Model psychotherapy in the alleviation of craving and cognitive improvement of participants with methamphetamine use disorder.

METHODS

In a randomized and sham-controlled trial, 60 male participants were assigned to Matrix psychotherapy only, sham tDCS plus Matrix, or active tDCS plus Matrix. Sixteen sessions of 20-min anodal (2 mA over F3 for targeting the left DLPFC) or sham tDCS along were administered in the outpatient setting. Pre- and post-intervention craving, executive functioning, and working memory were assessed using the Obsessive-Compulsive Drug Use Scale, Wisconsin Card Sorting Test, and Wechsler Memory Scale, respectively. One month following the interventions relapse was investigated by urine drug screen or interview.

RESULTS

In comparison with sham tDCS (n = 12) and Matrix psychotherapy only group (n = 13), the active tDCS group (n = 15) showed more reduction in craving (p<.05, η² = .21). Auditory and visual memory (Wechsler) and true answers and false answers (WCST) significantly improved in the active tDCS group (η2 = .18, η2 = 12, η2 = 03, η2 = .02, respectively) but not in the other groups. Relapse rates did not significantly differ between groups (p = .17). A significant correlation was found between craving reduction and cognitive functioning in the active tDCS group.

CONCLUSION

The combination of Matrix Model psychotherapy and tDCS may an effective therapy for cognitive improvement and craving in participants with methamphetamine use disorder.

CLINICAL TRIALS REGISTRY

This study was registered at the Iranian Registry of Clinical Trials (IRCT20161026030510N3).

Dissociating the role of dACC and dlPFC for emotion appraisal and mood regulation using cathodal tDCS

Several neuroimaging studies have shown that a distributed network of brain regions is involved in our ability to appraise the emotions we experience in daily life. In particular, scholars suggested that the dorsal anterior cingulate cortex (dACC) may play a role in the appraisal of emotional stimuli together with subcortical regions, especially when stimuli are negatively valenced, and the dorsolateral prefrontal cortex (dlPFC) may play a role in regulating emotions. However, proofs of the causal role of these regions are lacking. In the present study, we aim at testing this model by stimulating both the dACC and the left dlPFC via cathodal tDCS. Twenty-four participants were asked to attend and rate the arousal and valence of negative and neutral emotional stimuli (pictures and words) in three different experimental sessions: cathodal stimulation of dACC, left dlPFC, or sham. In addition to the experimental task, the baseline affective state was measured before and after the stimulation to further assess the effect of stimulation over the baseline affective state after the experimental session. Results showed that cathodal stimulation of dACC, but not the left dlPFC, was associated with reduced arousal ratings of emotional stimuli, both compared with the sham condition. Moreover, cathodal stimulation of left dlPFC decreased participant's positive affective state after the session. These findings suggest for the first time, a dissociation between the dACC and dlPFC, with the former more involved in emotion appraisal, and the latter more involved in mood modulation.

Low Intensity Focused Ultrasound for Non-invasive and Reversible Deep Brain Neuromodulation-A Paradigm Shift in Psychiatric Research

This article describes an emerging non-invasive neuromodulatory technology, called low intensity focused ultrasound (LIFU). This technology is potentially paradigm shifting as it can deliver non-invasive and reversible deep brain neuromodulation through acoustic sonication, at millimeter precision. Low intensity focused ultrasound's spatial precision, yet non-invasive nature sets it apart from current technologies, such as transcranial magnetic or electrical stimulation and deep brain stimulation. Additionally, its reversible effects allow for the causal study of deep brain regions implicated in psychiatric illness. Studies to date have demonstrated that LIFU can safely modulate human brain activity at cortical and subcortical levels. Due to its novelty, most researchers and clinicians are not aware of the potential applications and promise of this technique, underscoring the need for foundational papers to introduce the community to LIFU. This mini-review and synthesis of recent advances examines several key papers on LIFU administered to humans, describes the population under study, parameters used, and relevant findings that may guide future research. We conclude with a concise overview of some of the more pressing questions to date, considerations when interpreting new data from an emerging field, and highlight the opportunities and challenges in this exciting new area of study.

Efficacy and safety of daily home-based transcranial direct current stimulation as adjunct treatment for bipolar depressive episodes: Double-blind sham-controlled randomized clinical trial

BACKGROUND

Although transcranial direct current stimulation (tDCS) is known to be a promising therapeutic modality for unipolar depression, the efficacy and safety of tDCS for bipolar depressive episodes (BD) are still unknown and clinical trials of home-based tDCS treatment are scarce. As a result, we set out to investigate the efficacy and safety of home-based tDCS for the treatment BD.

METHODS

Participants (n = 64), diagnosed as bipolar disorder as per the diagnostic and statistical manual of mental disorders (DSM-5), were randomly assigned to receive tDCS. Hamilton Depression Rating Scale (HDRS-17) scores were measured at the baseline, week 2, 4, and 6, and home-based tDCS (for 30 min with 2 mA) was self-administered daily.

RESULTS

Of the 64 patients (15.6% bipolar disorder I, 84.4% bipolar disorder II), 41 patients completed the entire assessment. In the intention-to-treat analysis, time-group interaction for the HDRS-17 [F _{(3, 146.36)} = 2.060; p = 0.108] and adverse effect differences between two groups were not statistically significant, except the pain score, which was higher in the active group than the sham group (week 0-2: p < 0.01, week 2-4: p < 0.05, and week 4-6: p < 0.01).

CONCLUSION

Even though we found no evidence for the efficacy of home-based tDCS for patients with BD, this tool was found to be a safe and tolerable treatment modality for BD.

CLINICAL TRIAL REGISTRATION

[https://clinicaltrials.gov/show/NCT03974815], identifier [NCT03974815].

A comparative study of the effect of electroconvulsive therapy and transcranial direct current stimulation in the treatment of persons suffering from treatment-resistant depression

BACKGROUND

About 20%-30% of persons with major depression are said to have treatment-resistant depression (TRD) when they do not respond to antidepressants. These people continue to suffer in life and have poor quality of life. Although electroconvulsive therapy (ECT) is the most successful option in treating TRD, many people refuse ECT due to various reasons (stigma, the cost involved, and medical complications). Various studies combine treatment options such as psychotherapy, repetitive trans magnetic stimulation, ketamine, and transcranial direct current stimulation (tDCS) in an attempt to reduce symptoms for those people suffering from TRD. This study aims to compare the effectiveness of ECT and tDCS in TRD.

SUBJECTS AND METHODS

A total of 90 persons suffering from TRD were selected for the study. 46 persons received 6 ECTs and 44 persons received 10 sessions of tDCS. Treatment response was measured using baseline and postassessment scores of Hamilton depression rating scale and clinical global impression. The scores were used to determine the effectiveness of ECT in comparison to tDCS in TRD.

STATISTICAL ANALYSIS

The mean ± standard deviation was analyzed and paired t-test was used to find the significance of treatment outcome in a group at a 95% confidence interval.

RESULTS

ECT was found to be more effective than tDCS in the reduction of depressive symptoms. tDCS showed a significant reduction in depressive symptoms (P < 0.001). ECT has yet again been proven to be effective in the treatment of TRD.

CONCLUSION AND DISCUSSION

tDCS is effective in reducing depressive symptoms in persons suffering from TRD. However, ECT is superior in decreasing depressive symptoms in TRD when compared to tDCS.

Home-Based Transcranial Direct Current Stimulation for the Treatment of Symptoms of Depression and Anxiety in Temporal Lobe Epilepsy: A Randomized, Double-Blind, Sham-Controlled Clinical Trial

We conducted a double-blind randomized clinical trial in order to examine the effects and the safety of home-based transcranial direct current stimulation (tDCS) on depressive and anxious symptoms of patients with temporal lobe epilepsy (TLE). We evaluated 26 adults with TLE and depressive symptoms randomized into two different groups: active tDCS (tDCSa) and Sham (tDCSs). The patients were first submitted to 20 sessions of tDCS for 20 min daily, 5 days a week for 4 weeks and then received a maintenance tDCS application in the research laboratory once a week for 3 weeks. The intensity of the current was 2 mA, applied bilaterally over the dorsolateral prefrontal cortex, with the anode positioned on the left side and the cathode on the right side. Participants were evaluated on days 1, 15, 30, and 60 of the study using the Beck Depression Inventory II (BDI). A follow-up evaluation was performed 1 year after the end of treatment. They were also evaluated for quality of life and for anxious symptoms as secondary outcomes. The groups did not differ in clinical, socioeconomic or psychometric characteristics at the initial assessment. There was no statistically significant difference between groups regarding reported adverse effects, seizure frequency or dropouts. On average, between the 1st and 60th day, the BDI score decreased by 43.93% in the active group and by 44.67% in the Sham group (ΔBDIfinal – initial = −12.54 vs. −12.20, p = 0.68). The similar improvement in depressive symptoms observed in both groups was attributed to placebo effect and interaction between participants and research group and not to tDCS intervention per se. In our study, tDCS was safe and well tolerated, but it was not effective in reducing depressive or anxiety symptoms in patients with temporal lobe epilepsy.

Clinical Trial Registration: [ClinicalTrials.gov], identifier [NCT03871842].

An artificial neural-network approach to identify motor hotspot for upper-limb based on electroencephalography: a proof-of-concept study

Background

To apply transcranial electrical stimulation (tES) to the motor cortex, motor hotspots are generally identified using motor evoked potentials by transcranial magnetic stimulation (TMS). The objective of this study is to validate the feasibility of a novel electroencephalography (EEG)-based motor-hotspot-identification approach using a machine learning technique as a potential alternative to TMS.

Methods

EEG data were measured using 63 channels from thirty subjects as they performed a simple finger tapping task. Power spectral densities of the EEG data were extracted from six frequency bands (delta, theta, alpha, beta, gamma, and full) and were independently used to train and test an artificial neural network for motor hotspot identification. The 3D coordinate information of individual motor hotspots identified by TMS were quantitatively compared with those estimated by our EEG-based motor-hotspot-identification approach to assess its feasibility.

Results

The minimum mean error distance between the motor hotspot locations identified by TMS and our proposed motor-hotspot-identification approach was 0.22 ± 0.03 cm, demonstrating the proof-of-concept of our proposed EEG-based approach. A mean error distance of 1.32 ± 0.15 cm was measured when using only nine channels attached to the middle of the motor cortex, showing the possibility of practically using the proposed motor-hotspot-identification approach based on a relatively small number of EEG channels.

Conclusion

We demonstrated the feasibility of our novel EEG-based motor-hotspot-identification method. It is expected that our approach can be used as an alternative to TMS for motor hotspot identification. In particular, its usability would significantly increase when using a recently developed portable tES device integrated with an EEG device.

Standard Non-Personalized Electric Field Modeling of Twenty Typical tDCS Electrode Configurations via the Computational Finite Element Method: Contributions and Limitations of Two Different Approaches

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation procedure to modulate cortical excitability and related brain functions. tDCS can effectively alter multiple brain functions in healthy humans and is suggested as a therapeutic tool in several neurological and psychiatric diseases. However, variability of results is an important limitation of this method. This variability may be due to multiple factors, including age, head and brain anatomy (including skull, skin, CSF and meninges), cognitive reserve and baseline performance level, specific task demands, as well as comorbidities in clinical settings. Different electrode montages are a further source of variability between tDCS studies. A procedure to estimate the electric field generated by specific tDCS electrode configurations, which can be helpful to adapt stimulation protocols, is the computational finite element method. This approach is useful to provide a priori modeling of the current spread and electric field intensity that will be generated according to the implemented electrode montage. Here, we present standard, non-personalized model-based electric field simulations for motor, dorsolateral prefrontal, and posterior parietal cortex stimulation according to twenty typical tDCS electrode configurations using two different current flow modeling software packages. The resulting simulated maximum intensity of the electric field, focality, and current spread were similar, but not identical, between models. The advantages and limitations of both mathematical simulations of the electric field are presented and discussed systematically, including aspects that, at present, prevent more widespread application of respective simulation approaches in the field of non-invasive brain stimulation.

Impact of bifrontal home-based transcranial direct current stimulation in pain catastrophizing and disability due to pain in fibromyalgia: a randomized, double-blind sham-controlled study

This randomized, double-blind trial tested the hypothesis that twenty sessions of home-based anodal(a)-transcranial direct current stimulation (tDCS) (2mA for 20 min) bifrontal, with anodal on the left dorsolateral prefrontal cortex (l-DLPFC) would be better than sham-(s)-tDCS to reduce scores on Pain Catastrophizing Scale (PCS) and disability-related to pain (DRP) assessed by the Profile of Chronic Pain: Screen (PCP:S) (primary outcomes). Secondary outcomes were depressive symptoms, sleep quality, heat pain threshold (HPT), heat pain tolerance (HPTo), and serum brain-derived-neurotrophic-factor (BDNF). Forty-eight women with fibromyalgia, 30-65 years-old were randomized into 2:1 groups [a-tDCS (n=32) or s-tDCS (n=16)]. Post hoc analysis revealed that a-tDCS reduced the PCS total scores by 51.38% compared to 26.96% in s-tDCS, and a-tDCS reduced PCP:S total scores by 31.43% compared to 19.15% in s-tDCS. The a-tDCS improved depressive symptoms, sleep quality and increased the HPTo. The delta-value in the serum BDNF (mean post treatment end minus pre-treatment) was conversely correlated with the a-tDCS effect in pain catastrophizing. In contrast, the a-tDCS impact on reducing the DRP at the treatment end was positively associated with a reduction in the serum BDNF and improvement of depressive symptoms, sleep quality and pain catastrophizing symptoms. PERSPECTIVE: Home-based bifrontal tDCS with a-tDCS on the l-DLPFC are associated with a moderate effect size (ES) in the following outcomes: (i) Decreased rumination and magnification of pain catastrophizing. (ii) Improved the disability for daily activities due to fibromyalgia symptoms. Overall, these findings support the feasibility of self-applied home-based tDCS on DLPFC to improve fibromyalgia symptoms.

Temporal Interference Stimulation Regulates Eye Movements and Neural Activity in the Mice Superior Colliculus. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021;2021:6231-6234. [PMID: 34892538 DOI: 10.1109/embc46164.2021.9629968]

Temporal interference (TI) stimulation is a novel electrical stimulation technique which offers noninvasive deep brain stimulation (NDBS) in mice. The purpose of this study is to investigate the effect of TI stimulation on deep layers superior colliculus (SC) nerve activity and eye movements in mice. Six male C57BL / 6J mice were used in this study. Different parameters of TI stimulation were applied to the deep layers of mice SC. Each TI stimulation lasted for 20 seconds and were repeated five times. We analyzed the synchronous recording of Ca²⁺ signals in deep layers mice SC and the eye movement amplitudes. Our results show that TI stimulation can evoke eye movements and the neural activity in deep layers of mice SC. Changing the difference frequency of TI stimulation can regulate the frequency of the nerve activity and eye movements. Granger causality analysis indicates that the neural activity in deep layers of mice SC may cause the eye movements during TI stimulation.

Therapeutic Neurostimulation in Obsessive-Compulsive and Related Disorders: A Systematic Review

Invasive and noninvasive neurostimulation therapies for obsessive-compulsive and related disorders (OCRD) were systematically reviewed with the aim of assessing clinical characteristics, methodologies, neuroanatomical substrates, and varied stimulation parameters. Previous reviews have focused on a narrow scope, statistical rather than clinical significance, grouped together heterogenous protocols, and proposed inconclusive outcomes and directions. Herein, a comprehensive and transdiagnostic evaluation of all clinically relevant determinants is presented with translational clinical recommendations and novel response rates. Electroconvulsive therapy (ECT) studies were limited in number and quality but demonstrated greater efficacy than previously identified. Targeting the pre-SMA/SMA is recommended for transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS). TMS yielded superior outcomes, although polarity findings were conflicting, and refinement of frontal/cognitive control protocols may optimize outcomes. For both techniques, standardization of polarity, more treatment sessions (>20), and targeting multiple structures are encouraged. A deep brain stimulation (DBS) 'sweet spot' of the striatum for OCD was proposed, and CBT is strongly encouraged. Tourette's patients showed less variance and reliance on treatment optimization. Several DBS targets achieved consistent, rapid, and sustained clinical response. Analysis of fiber connectivity, as opposed to precise neural regions, should be implemented for target selection. Standardization of protocols is necessary to achieve translational outcomes.

Wearable Transcranial Ultrasound System for Remote Stimulation of Freely Moving Animal

OBJECTIVE

Transcranial focused ultrasound (tFUS) has drawn considerable attention in the neuroscience field as a noninvasive approach to modulate brain circuits. However, the conventional approach requires the use of anesthetized or immobilized animal models, which places considerable restrictions on behavior and affects treatment. Thus, this work presents a wireless, wearable system to achieve ultrasound brain stimulation in freely behaving animals.

METHODS

The wearable tFUS system was developed based on a microcontroller and amplifier circuit. Brain activity induced by tFUS was monitored through cerebral hemodynamic changes using near-infrared spectroscopy. The system was also applied to stroke rehabilitation after temporal middle cerebral artery occlusion (tMCAO) in rats. Temperature calculations and histological results showed the safety of the application even with prolonged 40 min sonication.

RESULTS

The output ultrasonic wave produced from a custom PZT transducer had a central frequency of 457 kHz and peak to peak pressure of 426 kPa. The device weight was 20 g, allowing a full range of motion. The stimulation was found to induce hemodynamic changes in the sonicated area, while open-field tests showed that ultrasound applied to the ipsilateral hemisphere for 5 consecutive days after the stroke facilitated recovery.

CONCLUSION

The wearable tFUS system has been designed and implemented on moving rats. The results showed the ability of device to cause both short- and long lasting effects.

SIGNIFICANCE

The proposed device provides a more natural environment to investigate the effects of tFUS for behavioral and long-term studies.

Determining the effects of transcranial direct current stimulation on tinnitus and tinnitus-related outcomes: protocol for a systematic review

INTRODUCTION

Tinnitus is the awareness of a sound in the ear or head in the absence of an external source. It affects around 10%-15% of people. About 20% of people with tinnitus also experience symptoms such as depression or anxiety that negatively affect their life. Transcranial direct current stimulation (tDCS) is a technique involving constant low-intensity direct current delivered via electrodes on the head. It is postulated to modulate (suppress or enhance) neural activity in the region between electrodes. As such, it represents a potential treatment option for tinnitus, as well as comorbid depression or anxiety. This systematic review will estimate the effects of tDCS on outcomes relevant to tinnitus. In addition, it will determine whether there is any relationship between stimulation parameters (electrode montage, current intensity, and length and frequency of stimulation sessions) and the effect of tDCS on these outcomes.

METHODS AND ANALYSIS

Electronic searches for peer-reviewed journal articles will be performed in the Cochrane Register of Studies online (the Cochrane Ear, Nose and Throat Disorders Group Register and CENTRAL, current issue), PubMed, EMBASE, CINAHL, LILACS, KoreaMed, IndMed, PakMediNet, CNKI, AMED, PsycINFO, Web of Science, ClinicalTrials.gov, ICTRP and Google Scholar using the following search terms: transcranial Direct Current Stimulation OR tDCS AND tinnitus OR depression OR anxiety OR quality of life OR adverse effects OR neurophys*.Searches were not limited by date. Methods are reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols (PRISMA-P). Randomised controlled trials will be included if they report at least one of the following outcomes: tinnitus symptom severity, anxiety or depression as measured by relevant validated instruments. Where available, data on quality of life, adverse effects and neurophysiological changes will also be reviewed. In addition to an analysis of the effect of each parameter, an analysis will be performed to uncover any interactions between parameters. Where appropriate, meta-analyses will be performed.

ETHICS AND DISSEMINATION

This systematic review will make use of secondary data only. As no data will be obtained from participants directly, ethical approval has not been sought. No other ethical issues are foreseen. Findings will be submitted for peer-reviewed publication and presented at academic conferences. The results of this review will inform future research.

PROSPERO REGISTRATION NUMBER

CRD42020185567.

Magnetic resonance spectroscopy with transcranial direct current stimulation to explore the underlying biochemical and physiological mechanism of the human brain: A systematic review

A large body of molecular and neurophysiological evidence connects synaptic plasticity to specific functions and energy metabolism in particular areas of the brain. Furthermore, altered plasticity and energy regulation has been associated with a number of neuropsychiatric disorders. A favourable approach enabling the modulation of neuronal excitability and energy in humans is to stimulate the brain using transcranial direct current stimulation (tDCS) and then to observe the effect on neurometabolites using magnetic resonance spectroscopy (MRS). In this way, a well-defined modulation of brain energy and excitability can be achieved using a dedicated tDCS protocol to a predetermined brain region. This systematic review was guided by the preferred reporting items for systematic reviews and meta-analysis and summarises recent literature studying the effect of tDCS on neurometabolites in the human brain as measured by proton or phosphorus MRS. Limitations and recommendations are discussed for future research. The findings of this review provide clear evidence for the potential of using tDCS and MRS to examine and understand the effect of neurometabolites in the in vivo human brain.

Effect of transcranial direct current stimulation on post-stroke fatigue

Background

Fatigue is one of the most commonly reported symptoms post-stroke, which has a severe impact on the quality of life. Post-stroke fatigue is associated with reduced motor cortical excitability, specifically of the affected hemisphere.

Objective

The aim of this exploratory study was to assess whether fatigue symptoms can be reduced by increasing cortical excitability using anodal transcranial direct current stimulation (tDCS).

Methods

In this sham-controlled, double-blind intervention study, tDCS was applied bilaterally over the primary motor cortex in a single session in thirty stroke survivors with high severity of fatigue. A questionnaire-based measure of trait fatigue (primary outcome) was obtained before, after a week and 5 weeks post stimulation. Secondary outcome measures of state fatigue, motor cortex neurophysiology and perceived effort were also assessed pre, immediately post, a week and 5 weeks post stimulation.

Results

Anodal tDCS significantly improved fatigue symptoms a week after real stimulation when compared to sham stimulation. There was also a significant change in motor cortex neurophysiology of the affected hemisphere and perceived effort, a week after stimulation. The degree of improvement in fatigue was associated with baseline anxiety levels.

Conclusion

A single session of anodal tDCS improves fatigue symptoms with the effect lasting up to a week post stimulation. tDCS may therefore be a useful tool for managing fatigue symptoms post-stroke.

Trial registration

NCT04634864

Date of registration

17/11/2020–“retrospectively registered”.

Neurobiological After-Effects of Low Intensity Transcranial Electric Stimulation of the Human Nervous System: From Basic Mechanisms to Metaplasticity

Non-invasive low-intensity transcranial electrical stimulation (tES) of the brain is an evolving field that has brought remarkable attention in the past few decades for its ability to directly modulate specific brain functions. Neurobiological after-effects of tES seems to be related to changes in neuronal and synaptic excitability and plasticity, however mechanisms are still far from being elucidated. We aim to review recent results from in vitro and in vivo studies that highlight molecular and cellular mechanisms of transcranial direct (tDCS) and alternating (tACS) current stimulation. Changes in membrane potential and neural synchronization explain the ongoing and short-lasting effects of tES, while changes induced in existing proteins and new protein synthesis is required for long-lasting plastic changes (LTP/LTD). Glial cells, for decades supporting elements, are now considered constitutive part of the synapse and might contribute to the mechanisms of synaptic plasticity. This review brings into focus the neurobiological mechanisms and after-effects of tDCS and tACS from in vitro and in vivo studies, in both animals and humans, highlighting possible pathways for the development of targeted therapeutic applications.

High definition transcranial direct current stimulation (HD-tDCS): A systematic review on the treatment of neuropsychiatric disorders

HD-tDCS (High-definition transcranial direct current stimulation) is a novel non-invasive brain stimulation (NIBS) technique based on the principle that when weak intensity electric currents are targeted on specific areas of the scalp, they cause underlying cortical stimulation. HD-tDCS shares its technical methodology with conventional tDCS (montage comprising of one anode and one cathode) except for a few modifications that are believed to have focal and longer-lasting neuromodulation effects. Although HD-tDCS is a recently available NIBS technique, impactful studies, case reports, and few controlled trials have been conducted in this context, facilitating an understanding of its neurobiological effects and the clinical translation of the same in health care set-up. The current article narratively reviews the mechanism of action of HD-tDCS, and it systematically examines the cognitive, clinical, and neurobiological effects of HD-tDCS in healthy volunteers as well as patients with neuropsychiatric conditions. Thus, this review attempts to explore the role of HD-tDCS in present-day practice and the future in the context of various neurological and psychiatric disorders.

Past, Present, and Future of Non-invasive Brain Stimulation Approaches to Treat Cognitive Impairment in Neurodegenerative Diseases: Time for a Comprehensive Critical Review

Low birth rates and increasing life expectancy experienced by developed societies have placed an unprecedented pressure on governments and the health system to deal effectively with the human, social and financial burden associated to aging-related diseases. At present, ∼24 million people worldwide suffer from cognitive neurodegenerative diseases, a prevalence that doubles every five years. Pharmacological therapies and cognitive training/rehabilitation have generated temporary hope and, occasionally, proof of mild relief. Nonetheless, these approaches are yet to demonstrate a meaningful therapeutic impact and changes in prognosis. We here review evidence gathered for nearly a decade on non-invasive brain stimulation (NIBS), a less known therapeutic strategy aiming to limit cognitive decline associated with neurodegenerative conditions. Transcranial Magnetic Stimulation and Transcranial Direct Current Stimulation, two of the most popular NIBS technologies, use electrical fields generated non-invasively in the brain to long-lastingly enhance the excitability/activity of key brain regions contributing to relevant cognitive processes. The current comprehensive critical review presents proof-of-concept evidence and meaningful cognitive outcomes of NIBS in eight of the most prevalent neurodegenerative pathologies affecting cognition: Alzheimer's Disease, Parkinson's Disease, Dementia with Lewy Bodies, Primary Progressive Aphasias (PPA), behavioral variant of Frontotemporal Dementia, Corticobasal Syndrome, Progressive Supranuclear Palsy, and Posterior Cortical Atrophy. We analyzed a total of 70 internationally published studies: 33 focusing on Alzheimer's disease, 19 on PPA and 18 on the remaining neurodegenerative pathologies. The therapeutic benefit and clinical significance of NIBS remains inconclusive, in particular given the lack of a sufficient number of double-blind placebo-controlled randomized clinical trials using multiday stimulation regimes, the heterogeneity of the protocols, and adequate behavioral and neuroimaging response biomarkers, able to show lasting effects and an impact on prognosis. The field remains promising but, to make further progress, research efforts need to take in account the latest evidence of the anatomical and neurophysiological features underlying cognitive deficits in these patient populations. Moreover, as the development of in vivo biomarkers are ongoing, allowing for an early diagnosis of these neuro-cognitive conditions, one could consider a scenario in which NIBS treatment will be personalized and made part of a cognitive rehabilitation program, or useful as a potential adjunct to drug therapies since the earliest stages of suh diseases. Research should also integrate novel knowledge on the mechanisms and constraints guiding the impact of electrical and magnetic fields on cerebral tissues and brain activity, and incorporate the principles of information-based neurostimulation.