Attention improvement to transcranial alternating current stimulation at gamma frequency over the right frontoparietal network: a preliminary report.

Applying transcranial alternating current stimulation (tACS) at 40 Hz to the frontal and parietal regions, either unilaterally (left or right) or bilaterally, can improve cognitive dysfunctions. This study aimed to explore the influence of tACS at gamma frequency over right fronto-parietal (FP) region on attention. The analysis is based on retrospective data from a clinical intervention. We administered test of variables of attention (TOVA; visual mode) to 44 participants with various neuropsychiatric diagnoses before and after 12 sessions of tACS treatment. Alternating currents at 2.0 mA were delivered to the electrode positions F4 and P4, following the 10-20 EEG convention, for 20 mins in each session. We observed significant improvement across 3 indices of the TOVA, including reduction of variability in reaction time (p = 0.0002), increase in d-Prime (separability of targets and non-targets; p = 0.0157), and decrease in commission error rate (p = 0.0116). The mean RT and omission error rate largely remained unchanged. Artificial injection of tACS at 40 Hz over right FP network may improve attention function, especially in the domains of consistency in performance, target/non-target discrimination, and inhibitory control.

Comparison of short- and long-term effects of neurofeedback and transcranial electrical stimulation on the motor learning in healthy adults.

Researchers are exploring non-invasive neuromodulation techniques like transcranial direct current stimulation (tDCS) and neurofeedback (NFB) for enhancing motor learning. While tDCS modulates brain excitability using exogenous electric fields, NFB is an endogenous brain stimulation technique that enables individuals to regulate brain excitability in a closed-loop system. Despite their differing mechanisms, a direct comparison of their effects on motor learning is lacking. This study aimed to compare tDCS and NFB on online learning, short-term offline learning, and long-term offline learning in healthy participants, seeking to identify the most effective method for motor learning enhancement. In this parallel, randomized, single-blinded, controlled trial, 100 healthy participants were randomly assigned to one of five groups: real tDCS, sham tDCS, real NFB, sham NFB, and passive control. Primary outcomes included normalized reaction time (NRT), normalized response accuracy (NRA), and normalized skill index (NSI), measured through a serial reaction time task. Secondary outcomes involved physical and mental fatigue, assessed using a visual analog scale. The study involved 14 blocks of 80 trials each. Online learning was assessed by changes in NRT, NRA, and NSI between Block 3 and Block 9. Short-term and long-term offline learning were evaluated by changes in these measures between Block 9 and Block 11, and between Block 9 and Block 13, respectively. RESULTS: showed a significant decrease in NRA in the sham tDCS and passive control groups from block 3-9, with no changes in other groups. NRT significantly decreased in all intervention groups from block 9-11, with no change in the control group. The NSI significantly increased across all intervention groups between blocks 9 and 11, with large to very large effect sizes, while the passive control group saw a medium effect size increase. Furthermore, NRA significantly increased in the real NFB and real tDCS groups from block 9 to block 13. NRT also significantly decreased in all intervention groups when comparing block 13 to block 9, while the passive control group showed no significant changes. Notably, the reduction in NRT from block 9 to block 13 was significantly greater in the real tDCS group than in the control group, with a mean difference of 0.087 (95 % CI: 0.004-0.169, p = 0.031). Additionally, NSI significantly increased in all intervention groups except the control group from block 9 to block 13. In conclusion, neither NFB nor tDCS had a significant positive impact on online learning. However, both real and sham versions of tDCS and NFB resulted in notable improvements in short-term offline learning. The difference in improvement between NFB and tDCS, as well as between real and sham interventions, was not statistically significant, suggesting that the placebo effect may play a significant role in enhancing short-term offline learning. For long-term offline learning, both brain stimulation methods, particularly tDCS, showed positive effects, although the placebo effect also appeared to contribute.

Application of Transcranial Direct and Alternating Current Stimulation (tDCS and tACS) on Major Depressive Disorder.

The exploration of brain stimulation methods offers a promising avenue to overcome the shortcomings of traditional drug therapies and psychological treatments for major depressive disorder (MDD). Over the past years, there has been an increasing focus on transcranial electrical stimulation (tES), notably for its ease of use and potentially fewer side effects. This chapter delves into the use of transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), which are key components of tES, in managing depression. It begins by introducing tDCS and tACS, summarizing their action mechanisms. Following this introduction, the chapter provides an in-depth analysis of existing meta-analyses, systematic reviews, clinical studies, and case reports that have applied tES in MDD treatment. It also considers the role of tES in personalized medicine by looking at specific patient groups and evaluating research on possible biomarkers that could predict how patients with MDD respond to tES therapy.

Is non-invasive neuromodulation a viable technique to improve neuroplasticity in individuals with acquired brain injury? A review.

Objective: This study aimed to explore and evaluate the efficacy of non-invasive brain stimulation (NIBS) as a standalone or coupled intervention and understand its mechanisms to produce positive alterations in neuroplasticity and behavioral outcomes after acquired brain injury (ABI). Data sources: Cochrane Library, Web of Science, PubMed, and Google Scholar databases were searched from January 2013 to January 2024. Study selection: Using the PICO framework, transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) randomized controlled trials (RCTs), retrospective, pilot, open-label, and observational large group and single-participant case studies were included. Two authors reviewed articles according to pre-established inclusion criteria. Data extraction: Data related to participant and intervention characteristics, mechanisms of change, methods, and outcomes were extracted by two authors. The two authors performed quality assessments using SORT. Results: Twenty-two studies involving 657 participants diagnosed with ABIs were included. Two studies reported that NIBS was ineffective in producing positive alterations or behavioral outcomes. Twenty studies reported at least one, or a combination of, positively altered neuroplasticity and improved neuropsychological, neuropsychiatric, motor, or somatic symptoms. Twenty-eight current articles between 2020 and 2024 have been studied to elucidate potential mechanisms of change related to NIBS and other mediating or confounding variables. Discussion: tDCS and TMS may be efficacious as standalone interventions or coupled with neurorehabilitation therapies to positively alter maladaptive brain physiology and improve behavioral symptomology resulting from ABI. Based on postintervention and follow-up results, evidence suggests NIBS may offer a direct or mediatory contribution to improving behavioral outcomes post-ABI. Conclusion: More research is needed to better understand the extent of rTMS and tDCS application in affecting changes in symptoms after ABI.

Alpha transcranial alternating current stimulation as add-on to neglect training: a randomized trial.

Visuospatial neglect is a common and debilitating condition following unilateral stroke, significantly impacting cognitive functioning and daily life. There is an urgent need for effective treatments that can provide clinically relevant and sustained benefits. In addition to traditional stroke treatment, non-invasive brain stimulation, such as transcranial alternating current stimulation, shows promise as a complementary approach to enhance stroke recovery. In the current study, we aimed to evaluate the additive effects of multi-session transcranial alternating current stimulation at alpha frequency when combined with visual scanning training in chronic stroke patients with visuospatial neglect. In this double-blind randomized controlled trial, we compared the effects of active transcranial alternating current stimulation at alpha frequency to sham (placebo) transcranial alternating current stimulation, both combined with visual scanning training. Both groups received eighteen 40-minute training sessions over a 6-week period. A total of 22 chronic visuospatial neglect patients participated in the study (active group n = 12, sham group n = 10). The median age was 61.0 years, with a median time since stroke of 36.1 months. We assessed the patients at six time-points: at baseline, after the first, ninth and eighteenth training sessions, as well as 1 week and 3 months following the completion of the combined neuromodulation intervention. The primary outcome measure was the change in performance on a visual search task, specifically the star cancellation task. Secondary outcomes included performance on a visual detection task, two line bisection tasks and three tasks evaluating visuospatial neglect in daily living. We found significantly improved visual search (primary outcome) and visual detection performance in the neglected side in the active transcranial alternating current stimulation group, compared to the sham transcranial alternating current stimulation group. We did not observe stimulation effects on line bisection performance nor in daily living. Time effects were observed on all but one outcome measures. Multi-session transcranial alternating current stimulation combined with visual scanning training may be a more effective treatment for chronic visuospatial neglect than visual scanning training alone. These findings provide valuable insights into novel strategies for stroke recovery, even long after the injury, with the aim of enhancing cognitive rehabilitation outcomes and improving the overall quality of life for individuals affected by this condition. Trial registration: ClinicalTrials.gov; registration number: NCT05466487; https://clinicaltrials.gov/ct2/show/NCT05466487.

[An efficient and practical electrode optimization method for transcranial electrical stimulation].

Transcranial electrical stimulation (TES) is a non-invasive neuromodulation technique with great potential. Electrode optimization methods based on simulation models of individual TES field could provide personalized stimulation parameters according to individual variations in head tissue structure, significantly enhancing the stimulation accuracy of TES. However, the existing electrode optimization methods suffer from prolonged computation times (typically exceeding 1 d) and limitations such as disregarding the restricted number of output channels from the stimulator, further impeding their clinical applicability. Hence, this paper proposes an efficient and practical electrode optimization method. The proposed method simultaneously optimizes both the intensity and focality of TES within the target brain area while constraining the number of electrodes used, and it achieves faster computational speed. Compared to commonly used electrode optimization methods, the proposed method significantly reduces computation time by 85.9% while maintaining optimization effectiveness. Moreover, our method considered the number of available channels for the stimulator to distribute the current across multiple electrodes, further improving the tolerability of TES. The electrode optimization method proposed in this paper has the characteristics of high efficiency and easy operation, potentially providing valuable supporting data and references for the implementation of individualized TES.

Application of swallowing-feeding management combined with transcranial electrical stimulation in patients with mild craniocerebral trauma with dysphagia.

BACKGROUND: Mild craniocerebral trauma (CCT) can lead to various neurological and functional impairments, including dysphagia. Dysphagia refers to difficulties with swallowing, which can significantly impact a person's ability to eat, drink, and maintain proper nutrition. OBJECTIVE: To explore the application of swallowing-feeding management combined with transcranial electrical stimulation in CCT patients with dysphagia. METHODS: 110 patients with mild craniocerebral trauma with dysphagia treated in our hospital from January 2021 to August 2022 were divided into two groups: Combined transcranial electrical stimulation with swallowing-feeding management group (n = 55) and swallowing-feeding management group (n = 55). The clinical data, clinical efficacy, swallowing function and nutritional status before treatment and 2, 4 and 6 weeks after treatment were compared between the two groups. RESULTS: The combined treatment group exhibited significantly superior therapeutic outcomes compared to the swallowing-feeding management group (χ2=6.346, P=0.042). Notably, following treatment, patients in the combined treatment group demonstrated notably improved swallowing function in contrast to those in the swallowing-feeding management group (Treatment duration: 2 weeks, t=5.145, P<0.0001; 4 weeks, t=12.756, P<0.0001; 6 weeks, t=25.968, P<0.0001). Additionally, post-treatment, patients in the combined treatment group exhibited significantly enhanced nutritional status compared to those in the swallowing-feeding management group (χ2=14.611, P=0.002). CONCLUSION: Swallowing-feeding management combined with transcranial electrical stimulation is effective in CCT patients with dysphagia.

Non-invasive Brain Stimulation for Post-COVID-19 Conditions: A Systematic Review.

BACKGROUND: Alongside the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic, the number of patients with persistent symptoms following acute infection with SARS-CoV-2 is of concern. It is estimated that at least 65 million people worldwide meet criteria for what the World Health Organization (WHO) defines as "post-COVID-19 condition" - a multisystem disease comprising a wide range of symptoms. Effective treatments are lacking. In the present review, we aim to summarize the current evidence for the effectiveness of non-invasive or minimally invasive brain stimulation techniques in reducing symptoms of post-COVID-19. METHODS: After pre-registration with PROSPERO, the review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Guidelines (PRISMA). The four electronic databases PubMed/MEDLINE, PsycINFO, Web of Science and Scopus were systematically searched for all relevant studies through April 2nd, 2024. Two independent investigators selected empirical papers that reported on the application of non- or minimally invasive brain stimulation in patients with post-COVID-19 conditions. RESULTS: A total of 19 studies were identified, one using transcutaneous vagus nerve stimulation (tVNS), another using transorbital alternating current stimulation (toACS), 6 studies on transcranial magnetic stimulation (TMS) and 11 studies on transcranial direct current stimulation (tDCS) for the treatment of post-COVID-19 symptoms. CONCLUSIONS: Existing studies report first promising results, illustrating improvement in clinical outcome parameters. Yet, the mechanistic understanding of post-COVID-19 and how brain stimulation techniques may be benefitial are limited. Directions for future research in the field are discussed.

Impact of transcranial electrical stimulation on simultaneous stereoelectroencephalography recordings: A randomized sham-controlled study.

OBJECTIVE: Clinical exploitation of transcranial electrical stimulation for focal epilepsy treatment lacks quantification of the underlying neurophysiological changes. This study explores the immediate effects of transcranial alternating (tACS) and direct (tDCS) current stimulation on local and network brain activity using simultaneous stereoelectroencephalography (SEEG) recordings. METHODS: Patients were randomized for personalized tACS (n = 5) or tDCS (n = 6). Active stimulation (20 min) was preceded by sham stimulation (20 min). Changes in interictal epileptiform discharges (IED), functional connectivity (FC) and power spectral density (PSD) were quantified against baseline. RESULTS: Results demonstrated variable responses. Spike rate decreased in 2/6 subjects following sham and tDCS, while 2/6 showed an increase. Alpha power and aperiodic PSD components generally increased during and after tDCS but decreased following tACS. FC changes varied among subjects and were detectable even during sham sessions. CONCLUSIONS: Strong variability suggests that tES does not have a univocal effect on immediate changes in IED or FC, possibly due to the single session format and challenges in affecting subcortical areas. SIGNIFICANCE: This is the first study to examine intracranial FC changes during tACS and tDCS, highlighting the importance of sham comparisons and individual variability in tES response, offering valuable insights into its application for epilepsy treatment.

Pilot study of using transcranial temporal interfering theta-burst stimulation for modulating motor excitability in rat.

Transcranial temporal interference stimulation (tTIS) is a promising brain stimulation method that can target deep brain regions by delivering an interfering current from surface electrodes. Most instances of tTIS stimulate the brain with a single-frequency sinusoidal waveform generated by wave interference. Theta burst stimulation is an effective stimulation scheme that can modulate neuroplasticity by generating long-term potentiation- or depression-like effects. To broaden tTIS application, we developed a theta burst protocol using tTIS technique to modulate neuroplasticity in rats. Two cannula electrodes were unilaterally implanted into the intact skull over the primary motor cortex. Electrical field of temporal interference envelopes generated by tTIS through cannula electrodes were recorded from primary motor cortex. Theta burst schemes were characterized, and motor activation induced by the stimulation was also evaluated simultaneously by observing electromyographic signals from the corresponding brachioradialis muscle. After validating the stimulation scheme, we further tested the modulatory effects of theta burst stimulation delivered by tTIS and by conventional transcranial electrical stimulation on primary motor cortex excitability. Changes in the amplitude of motor evoked potentials, elicited when the primary motor cortex was activated by electrical pulses, were measured before and after theta burst stimulation by both techniques. Significant potentiation and suppression were found at 15 to 30 min after the intermittent and continuous theta burst stimulation delivered using tTIS, respectively. However, comparing to theta burst stimulations delivered using conventional form of transcranial electrical stimulation, using tTIS expressed no significant difference in modulating motor evoked potential amplitudes. Sham treatment from both methods had no effect on changing the motor evoked potential amplitude. The present study demonstrated the feasibility of using tTIS to achieve a theta burst stimulation scheme for motor cortical neuromodulation. These findings also indicated the future potential of using tTIS to carry out theta burst stimulation protocols in deep-brain networks for modulating neuroplasticity.

Transcranial alternating current stimulation for neuropsychiatric disorders: a systematic review of treatment parameters and outcomes.

Background: Transcranial alternating current stimulation (tACS) alters cortical excitability with low-intensity alternating current and thereby modulates aberrant brain oscillations. Despite the recent increase in studies investigating the feasibility and efficacy of tACS in treating neuropsychiatric disorders, its mechanisms, as well as optimal stimulation parameters, are not fully understood. Objectives: This systematic review aimed to compile human research on tACS for neuropsychiatric disorders to delineate typical treatment parameters for these conditions and evaluate its outcomes. Methods: A search for published studies and unpublished registered clinical trials was conducted through OVID (MEDLINE, PsycINFO, and Embase), ClinicalTrials.gov, and the International Clinical Trials Registry Platform. Studies utilizing tACS to treat neuropsychiatric disorders in a clinical trial setting were included. Results: In total, 783 published studies and 373 clinical trials were screened; 53 published studies and 70 clinical trials were included. Published studies demonstrated a low risk of bias, as assessed by the Joanna Briggs Institute Critical Appraisal Tools. Neurocognitive, psychotic, and depressive disorders were the most common disorders treated with tACS. Both published studies (58.5%) and registered clinical trials (52%) most commonly utilized gamma frequency bands and tACS was typically administered at an intensity of 2 mA peak-to-peak, once daily for 20 or fewer sessions. Although the targeted brain locations and tACS montages varied across studies based on the outcome measures and specific pathophysiology of the disorders, the dorsolateral prefrontal cortex (DLPFC) was the most common target in both published studies (30.2%) and registered clinical trials (25.6%). Across studies that published results on tACS outcome measures, tACS resulted in enhanced symptoms and/or improvements in overall psychopathology for neurocognitive (all 11 studies), psychotic (11 out of 14 studies), and depressive (7 out of 8 studies) disorders. Additionally, 17 studies reported alterations in the power spectrum of the electroencephalogram around the entrained frequency band at the targeted locations following tACS. Conclusion: Behavioral and cognitive symptoms have been positively impacted by tACS. The most consistent changes were reported in cognitive symptoms following gamma-tACS over the DLPFC. However, the paucity of neuroimaging studies for each neuropsychiatric condition highlights the necessity for replication studies employing biomarker- and mechanism-centric approaches.

Analgesia of noninvasive electrical stimulation of the dorsolateral prefrontal cortex: A systematic review and meta-analysis.

OBJECTIVE: The dorsolateral prefrontal cortex (DLPFC) is implicated in pain modulation, suggesting its potential as a therapeutic target for pain relief. However, studies on transcranial electrical stimulation (tES) over the DLPFC yielded diverse results, likely due to differences in stimulation protocols or pain assessment methods. This study aims to evaluate the analgesic effects of DLPFC-tES using a meta-analytical approach. METHODS: A meta-analysis of 29 studies involving 785 participants was conducted. The effects of genuine and sham DLPFC-tES on pain perception were examined in healthy individuals and patients with clinical pain. Subgroup analyses explored the impact of stimulation parameters and pain modalities. RESULTS: DLPFC-tES did not significantly affect pain outcomes in healthy populations but showed promise in reducing pain-intensity ratings in patients with clinical pain (Hedges' g = -0.78, 95% CI = [-1.33, -0.24], p = 0.005). Electrode placement significantly influenced the analgesic effect, with better results observed when the anode was at F3 and the cathode at F4. CONCLUSIONS: DLPFC-tES holds potential as a cost-effective pain management option, particularly for clinical populations. Optimizing electrode placement, especially with an symmetrical configuration, may enhance therapeutic efficacy. These findings underscore the promise of DLPFC-tES for alleviating perceived pain intensity in clinical settings, emphasizing the importance of electrode placement optimization.

Cognitive enhancement through technology: A review of transcranial electrical stimulation (TES) interventions in children and adolescents with specific learning disabilities.

BACKGROUND: In recent years, the exploration of innovative interventions for addressing problems of children and adolescents with specific learning disabilities (SLD) has garnered significant attention within the realm of neurocognitive research. Transcranial electrical stimulation (TES) has emerged as a promising tool for enhancing cognitive skills in children, offering a non-invasive and safe method that may particularly benefit those with learning difficulties. We aimed to appraise the extent and the quality of studies about impact of TES on cognitive skills including academic skills in children and adolescents with SLD. METHODS: A literature search was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Articles published between January 2000 and January 2024 were searched in PubMed, Embase, Scopus, Web of Science and Google Scholar. The study eligibility criteria were previously established according to the PICO model. The Physiotherapy Evidence Database (PEDro) scale and Cochrane Collaboration tool (ROB2) were used to assess the methodological quality and the risk of bias of the included studies, respectively. RESULTS: The initial search yielded 1571 studies among which 30 studies were systematically reviewed. The total number of participants was 224 individuals (intervention: 114; control: 110). Findings showed significant improvements in reading skills such as text reading, high-frequency word reading speed and efficiency and mathematical skills. Conversely, other cognitive skills such as working memory were not improved in people with dyslexia and dyscalculia. DISCUSSION: TES interventions can positively affect cognitive skills in children and adolescents with SLD; However, due to the small number of studies, medium methodological quality and high risk of bias, caution should be taken when interpreting the results.

Modulation of Alcohol Use Disorder by Brain Stimulation.

Currently available therapeutic modalities for alcohol use disorder (AUD) produce limited effect sizes or long-term compliance. Recent methods that were developed to modulate brain activity represent potential novel treatment options. Various methods of brain stimulation, when applied repeatedly, can induce long-term neurobiological, behavioral, and cognitive modifications. Recent studies in alcoholic subjects indicate the potential of brain stimulation methods to reduce alcohol craving, consumption, and relapse. Specifically, deep brain stimulation (DBS) of the nucleus accumbens or non-surgical stimulation of the dorsolateral prefrontal cortex (PFC) or medial PFC and anterior cingulate cortex using transcranial magnetic stimulation (TMS) has shown clinical benefit. However, further preclinical and clinical research is needed to establish understanding of mechanisms and the treatment protocols of brain stimulation for AUD. While efforts to design comparable apparatus in rodents continue, preclinical studies can be used to examine targets for DBS protocols, or to administer temporal patterns of pulsus similar to those used for TMS, to more superficial targets through implanted electrodes. The clinical field will benefit from studies with larger sample sizes, higher numbers of stimulation sessions, maintenance sessions, and long follow-up periods. The effect of symptoms provocation before and during stimulation should be further studied. Larger studies may have the power to explore predictive factors for the clinical outcome and thereby to optimize patient selection and eventually even develop personalization of the stimulation parameters.

Glaucoma Rehabilitation using ElectricAI Transcranial Stimulation (GREAT)-study protocol for randomized controlled trial using combined perceptual learning and transcranial electrical stimulation for vision enhancement.

BACKGROUND: Glaucoma patients with irreversible visual field loss often experience decreased quality of life, impaired mobility, and mental health challenges. Perceptual learning (PL) and transcranial electrical stimulation (tES) have emerged as promising interventions for vision rehabilitation, showing potential in restoring residual visual functions. The Glaucoma Rehabilitation using ElectricAI Transcranial stimulation (GREAT) project aims to investigate whether combining PL and tES is more effective than using either method alone in maximizing the visual function of glaucoma patients. Additionally, the study will assess the impact of these interventions on brain neural activity, blood biomarkers, mobility, mental health, quality of life, and fear of falling. METHODS: The study employs a three-arm, double-blind, randomized, superiority-controlled design. Participants are randomly allocated in a 1:1:1 ratio to one of three groups receiving: (1) real PL and real tES, (2) real PL and sham tES, and (3) placebo PL and sham tES. Each participant undergoes 10 sessions per block (~ 1 h each), with a total of three blocks. Assessments are conducted at six time points: baseline, interim 1, interim 2, post-intervention, 1-month post-intervention, and 2-month post-intervention. The primary outcome is the mean deviation of the 24-2 visual field measured by the Humphrey visual field analyzer. Secondary outcomes include detection rate in the suprathreshold visual field, balance and gait functions, and electrophysiological and biological responses. This study also investigates changes in neurotransmitter metabolism, biomarkers, self-perceived quality of life, and psychological status before and after the intervention. DISCUSSION: The GREAT project is the first study to assess the effectiveness of PL and tES in the rehabilitation of glaucoma. Our findings will offer comprehensive assessments of the impact of these treatments on a wide range of brain and vision-related metrics including visual field, neural activity, biomarkers, mobility, mental health, fear of falling, and quality of life. TRIAL REGISTRATION: ClinicalTrials.gov NCT05874258 . Registered on May 15, 2023.

The Role of Non-Invasive Brain Modulation in Identifying Disease Biomarkers for Diagnostic and Therapeutic Purposes in Parkinsonism.

Over the past three decades, substantial advancements have occurred in non-invasive brain stimulation (NIBS). These developments encompass various non-invasive techniques aimed at modulating brain function. Among the most widely utilized methods today are transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (TES), which include direct- or alternating-current transcranial stimulation (tDCS/tACS). In addition to these established techniques, newer modalities have emerged, broadening the scope of non-invasive neuromodulation approaches available for research and clinical applications in movement disorders, particularly for Parkinson's disease (PD) and, to a lesser extent, atypical Parkinsonism (AP). All NIBS techniques offer the opportunity to explore a wide range of neurophysiological mechanisms and exert influence over distinct brain regions implicated in the pathophysiology of Parkinsonism. This paper's first aim is to provide a brief overview of the historical background and underlying physiological principles of primary NIBS techniques, focusing on their translational relevance. It aims to shed light on the potential identification of biomarkers for diagnostic and therapeutic purposes, by summarising available experimental data on individuals with Parkinsonism. To date, despite promising findings indicating the potential utility of NIBS techniques in Parkinsonism, their integration into clinical routine for diagnostic or therapeutic protocols remains a subject of ongoing investigation and scientific debate. In this context, this paper addresses current unsolved issues and methodological challenges concerning the use of NIBS, focusing on the importance of future research endeavours for maximizing the efficacy and relevance of NIBS strategies for individuals with Parkinsonism.

A network meta-analysis of non-invasive brain stimulation interventions for autism spectrum disorder: Evidence from randomized controlled trials.

The efficacy and acceptability of various non-invasive brain stimulation (NIBS) interventions for autism spectrum disorder remain unclear. We carried out a systematic review for randomized controlled trials (RCTs) regarding NIBS for reducing autistic symptoms (INPLASY202370003). Sixteen articles (N = 709) met the inclusion criteria for network meta-analysis. Effect sizes were reported as standardized mean differences (SMDs) or odds ratios with 95 % confidence intervals (CIs). Fourteen active NIBS interventions, including transcranial direct current stimulation (tDCS), repetitive transcranial magnetic stimulation, and transcranial pulse stimulation were analyzed. Only anodal tDCS over the left dorsolateral prefrontal cortex paired with cathodal tDCS over an extracephalic location (atDCS_F3 + ctDCS_E) significantly improved autistic symptoms compared to sham controls (SMD = - 1.40, 95 %CIs = - 2.67 to - 0.14). None of the NIBS interventions markedly improved social-communication symptoms or restricted/repetitive behaviors in autistic participants. Moreover, no active NIBS interventions exhibited significant dropout rate differences compared to sham controls, and no serious adverse events were reported for any intervention.

Transcranial Electrical Stimulation: Clinical Implication and Practice for Treatment of Psychiatric Illness.

Brain electrical stimulation, particularly non-invasive brain stimulation (NIBS) techniques such as transcranial electrical stimulation (tES), have emerged as a promising treatment for various psychiatric disorders, including depression, anxiety, and post-traumatic stress disorder. tES techniques, such as transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), and transcranial random noise stimulation (tRNS), are cost-effective and safe interventions that are designed to affect neuronal circuits in the brain using various modalities. Although tES has shown effectiveness in the treatment of psychiatric disorders, there is a lack of comprehensive papers that consider its clinical implications. Therefore, this review aims to evaluate the clinical implications of tES and provide practical guidance for the treatment of psychiatric illnesses. Moreover, this review provides an overview of tES techniques and their mechanisms of action and summarizes recent clinical studies that have examined the use of tES for psychiatric disorders.

A Critical Review of Noninvasive Brain Stimulation Technologies in Alzheimer's Dementia and Primary Progressive Aphasia.

Multiple pharmacologic agents now have been approved in the United States and other countries as treatment to slow disease and clinical progression for Alzheimer's disease. Given these treatments have not been proven to lessen the cognitive deficits already manifested in the Alzheimer's Clinical Syndrome (ACS), and none are aimed for another debilitating dementia syndrome identified as primary progressive aphasia (PPA), there is an urgent need for new, safe, tolerable, and efficacious treatments to mitigate the cognitive deficits experienced in ACS and PPA. Noninvasive brain stimulation has shown promise for enhancing cognitive functioning, and there has been interest in its potential therapeutic value in ACS and PPA. This review critically examines the evidence of five technologies in ACS and PPA: transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), transcranial random noise stimulation (tRNS), repetitive transcranial magnetic stimulation (rTMS), and noninvasive vagus nerve stimulation (nVNS). Many randomized controlled trials of tDCS and rTMS report positive treatment effects on cognition in ACS and PPA that persist out to at least 8 weeks, whereas there are few trials for tACS and none for tRNS and nVNS. However, most positive trials did not identify clinically meaningful changes, underscoring that clinical efficacy has yet to be established in ACS and PPA. Much is still to be learned about noninvasive brain stimulation in ACS and PPA, and shifting the focus to prioritize clinical significance in addition to statistical significance in trials could yield greater success in understanding its potential cognitive effects and optimal parameters.