tDCS effects on task-related activation and working memory performance in traumatic brain injury: A within group randomized controlled trial

The Effects of Transcranial Direct Current Stimulation (tDCS) on the Cognitive Functions: A Systematic Review and Meta-analysis

Previous studies have investigated the effect of transcranial direct current stimulation (tDCS) on cognitive functions. However, these studies reported inconsistent results due to differences in experiment design, measurements, and stimulation parameters. Nonetheless, there is a lack of meta-analyses and review studies on tDCS and its impact on cognitive functions, including working memory, inhibition, flexibility, and theory of mind. We performed a systematic review and meta-analysis of tDCS studies published from the earliest available data up to October 2021, including studies reporting the effects of tDCS on cognitive functions in human populations. Therefore, these systematic review and meta-analysis aim to comprehensively analyze the effects of anodal and cathodal tDCS on cognitive functions by investigating 69 articles with a total of 5545 participants. Our study reveals significant anodal tDCS effects on various cognitive functions. Specifically, we observed improvements in working memory reaction time (RT), inhibition RT, flexibility RT, theory of mind RT, working memory accuracy, theory of mind accuracy and flexibility accuracy. Furthermore, our findings demonstrate noteworthy cathodal tDCS effects, enhancing working memory accuracy, inhibition accuracy, flexibility RT, flexibility accuracy, theory of mind RT, and theory of mind accuracy. Notably, regarding the influence of stimulation parameters of tDCS on cognitive functions, the results indicated significant differences across various aspects, including the timing of stimulation (online vs. offline studies), population type (clinical vs. healthy studies), stimulation duration (< 15 min vs. > 15 min), electrical current intensities (1-1.5 m.A vs. > 1.5 m.A), stimulation sites (right frontal vs. left frontal studies), age groups (young vs. older studies), and different cognitive tasks in each cognitive functioning aspect. In conclusion, our results demonstrate that tDCS can effectively enhance cognitive task performance, offering valuable insights into the potential benefits of this method for cognitive improvement.

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.

Evidence-Based Review of Randomized Controlled Trials of Interventions for Mental Health Management Post-Moderate to Severe Traumatic Brain Injury

OBJECTIVE

To present an evidence-based review of randomized controlled trials (RCTs) evaluating interventions for mental health post-moderate to severe traumatic brain injury (post-MSTBI), as part of an extensive database that has been conceptualized as a living systematic review.

METHODS

Systematic searches were conducted for RCTs published in the English language in MEDLINE, PubMed, Scopus, CINAHL, EMBASE, and PsycINFO, up to and including December 2022, in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The methodological quality of RCTs was assessed using the Physiotherapy Evidence Database scale, and the level of evidence was assigned using a modified Sackett scale.

RESULTS

Eighty-seven RCTs examining mental health interventions and outcome measures post-MSTBI were included. These studies collectively enrolled 6471 participants. A total of 41 RCTs (47.1%) were conducted in the United States and 56 studies (64.4%) were published after 2010. A total of 62 RCTs (71.3%) examined nonpharmacological interventions and 25 RCTs (28.7%) examined pharmacological interventions. Effective pharmacological treatments included desipramine and cerebrolysin; methylphenidate and rivastigmine showed conflicting evidence. Cognitive behavioral therapy (CBT) was found to be effective for hopelessness, stress, and anxiety, compared to usual care; however, it may be as effective as supportive psychotherapy for depression. CBT combined with motivational interviewing may be as effective as CBT combined with nondirective counseling for depression, stress, and anxiety. Acceptance and commitment therapy was effective for anxiety, stress, and depression. Tai Chi, dance, and walking appeared to be effective for depression and stress, while other nonpharmacological treatments such as peer mentoring showed limited effectiveness.

CONCLUSION

This evidence-based review provides a comprehensive overview of the research landscape of RCTs addressing mental health post-MSTBI. The findings from these RCTs may be valuable for health care professionals, researchers, and policymakers involved in the field of mental health and neurorehabilitation.

Exercise as a behavioral approach to improve mood in persons with traumatic brain injury

Mood disturbance is a common, long-term, negative consequence of traumatic brain injury (TBI) that is insufficiently addressed by most traditional treatment modalities. A large body of evidence supports the efficacy of exercise training (ET) to broadly improve mood, as measured most often by the Profile of Mood States (POMS). However, this behavioral approach is not used nearly enough in the TBI population, and when it is, mood is rarely measured. This scoping review will evaluate the use of POMS as a mood measure in TBI research and to establish a rationale for using ET as a behavioral approach to broadly improve mood in persons with TBI.

Efficacy of Non-Invasive Brain Stimulation for Treating Depression in Patients with Traumatic Brain Injury: A Meta-Analysis and Meta-Regression of Randomized Controlled Trials

OBJECTIVE

This meta-analysis aimed to ascertain the efficacy of non-invasive brain stimulation (NIBS)-comprising repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS)-for depression in traumatic brain injury (TBI) patients.

METHODS

Comprehensive searches were conducted in PubMed, Cochrane Database of Systematic Reviews, and the Cochrane Central Register of Controlled Trials up to 28 January 2023. Random-effects models assessed the treatment effects, and heterogeneity was evaluated through I2 statistics and funnel plot inspection.

RESULTS

From 10 trials (234 participants; 8 rTMS, 2 tDCS), NIBS was found significantly more effective than sham in alleviating depressive symptoms (SMD: 0.588, 95% CI: 0.264-0.912; p < 0.001). rTMS, specifically, showed higher efficacy (SMD: 0.707, 95% CI: 0.306-1.108; p = 0.001) compared to sham, whereas tDCS outcomes were inconclusive (SMD: 0.271, 95% CI: -0.230 to 0.771; p = 0.289). Meta-regression found no correlation with the number of sessions, treatment intensity, or total dose. Notably, while post-treatment effects were significant, they diminished 1-2 months post intervention. Adverse events associated with NIBS were minimal, with no severe outcomes like seizures and suicide reported.

CONCLUSIONS

rTMS emerged as a potent short-term intervention for depression in TBI patients, while tDCS findings remained equivocal. The long-term efficacy of NIBS is yet to be established, warranting further studies. The low adverse event rate reaffirms NIBS's potential safety.

Is transcranial direct current stimulation (tDCS) effective to improve cognition and functionality after severe traumatic brain injury? A perspective article and hypothesis

Severe traumatic brain injury (sTBI) is an important cause of disability and mortality and affects people of all ages. Current scientific evidence indicates that motor dysfunction and cognitive impairment are the main limiting factors in patients with sTBI. Transcranial direct current stimulation (tDCS) seems to be a good therapeutic option, but when it comes to patients with sTBI, the results are inconclusive, and some protocols have not yet been tested. In addition, there is still a lack of information on tDCS-related physiological mechanisms, especially during the acute phase. In the present study, based on current evidence on tDCS mechanisms of action, we hypothesized that performing tDCS sessions in individuals with sTBI, especially in the acute and subacute phases, together with conventional therapy sessions, could improve cognition and motor function in this population. This hypothesis presents a new possibility for treating sTBI, seeking to elucidate the extent to which early tDCS may affect long-term clinical outcomes.

A map of evidence using transcranial direct current stimulation (tDCS) to improve cognition in adults with traumatic brain injury (TBI)

Introduction

Cognition impairments often occur after a traumatic brain injury and occur at higher rates in military members. Cognitive symptoms impair daily function, including balance and life quality, years after the TBI. Current treatments to regain cognitive function after TBI, including medications and cognitive rehabilitation, have shown limited effectiveness. Transcranial direct current stimulation (tDCS) is a low-cost, non-invasive brain stimulation intervention that improves cognitive function in healthy adults and people with neuropsychologic diagnoses beyond current interventions. Despite the available evidence of the effectiveness of tDCS in improving cognition generally, only two small TBI trials have been conducted based on the most recent systematic review of tDCS effectiveness for cognition following neurological impairment. We found no tDCS studies that addressed TBI-related balance impairments.

Methods

A scoping review using a peer-reviewed search of eight databases was completed in July 2022. Two assessors completed a multi-step review and completed data extraction on included studies using a priori items recommended in tDCS and TBI research guidelines.

Results

A total of 399 results were reviewed for inclusion and 12 met the criteria and had data extracted from them by two assessors using Google Forms. Consensus on combined data results included a third assessor when needed. No studies using tDCS for cognition-related balance were found.

Discussion

Guidelines and technology measures increase the identification of brain differences that alter tDCS effects on cognition. People with mild-severe and acute-chronic TBI tolerated and benefited from tDCS. TBI-related cognition is understudied, and systematic research that incorporates recommended data elements is needed to advance tDCS interventions to improve cognition after TBI weeks to years after injury.

INCOG 2.0 Guidelines for Cognitive Rehabilitation Following Traumatic Brain Injury, Part V: Memory

INTRODUCTION

Memory impairments affecting encoding, acquisition, and retrieval of information after moderate-to-severe traumatic brain injury (TBI) have debilitating and enduring functional consequences. The interventional research reviewed primarily focused on mild to severe memory impairments in episodic and prospective memory. As memory is a common focus of cognitive rehabilitation, clinicians should understand and use the latest evidence. Therefore, the INCOG ("International Cognitive") 2014 clinical practice guidelines were updated.

METHODS

An expert panel of clinicians/researchers reviewed evidence published since 2014 and developed updated recommendations for intervention for memory impairments post-TBI, a decision-making algorithm, and an audit tool for review of clinical practice.

RESULTS

The interventional research approaches for episodic and prospective memory from 2014 are synthesized into 8 recommendations (6 updated and 2 new). Six recommendations are based on level A evidence and 2 on level B. In summary, they include the efficacy of choosing individual or multiple internal compensatory strategies, which can be delivered in a structured or individualized program. Of the external compensatory strategies, which should be the primary strategy for severe memory impairment, electronic reminder systems such as smartphone technology are preferred, with technological advances increasing their viability over traditional systems. Furthermore, microprompting personal digital assistant technology is recommended to cue completion of complex tasks. Memory strategies should be taught using instruction that considers the individual's functional and contextual needs while constraining errors. Memory rehabilitation programs can be delivered in an individualized or mixed format using group instruction. Computer cognitive training should be conducted with therapist guidance. Limited evidence exists to suggest that acetylcholinesterase inhibitors improve memory, so trials should include measures to assess impact. The use of transcranial direct current stimulation (tDCS) is not recommended for memory rehabilitation.

CONCLUSION

These recommendations for memory rehabilitation post-TBI reflect the current evidence and highlight the limitations of group instruction with heterogeneous populations of TBI. Further research is needed on the role of medications and tDCS to enhance memory.

INCOG 2.0 Guidelines for Cognitive Rehabilitation Following Traumatic Brain Injury, Part II: Attention and Information Processing Speed

INTRODUCTION

Moderate to severe traumatic brain injury (MS-TBI) commonly causes disruption in aspects of attention due to its diffuse nature and injury to frontotemporal and midbrain reticular activating systems. Attentional impairments are a common focus of cognitive rehabilitation, and increased awareness of evidence is needed to facilitate informed clinical practice.

METHODS

An expert panel of clinicians/researchers (known as INCOG) reviewed evidence published from 2014 and developed updated guidelines for the management of attention in adults, as well as a decision-making algorithm, and an audit tool for review of clinical practice.

RESULTS

This update incorporated 27 studies and made 11 recommendations. Two new recommendations regarding transcranial stimulation and an herbal supplement were made. Five were updated from INCOG 2014 and 4 were unchanged. The team recommends screening for and addressing factors contributing to attentional problems, including hearing, vision, fatigue, sleep-wake disturbance, anxiety, depression, pain, substance use, and medication. Metacognitive strategy training focused on everyday activities is recommended for individuals with mild-moderate attentional impairments. Practice on de-contextualized computer-based attentional tasks is not recommended because of lack of evidence of generalization, but direct training on everyday tasks, including dual tasks or dealing with background noise, may lead to gains for performance of those tasks. Potential usefulness of environmental modifications is also discussed. There is insufficient evidence to support mindfulness-based meditation, periodic alerting, or noninvasive brain stimulation for alleviating attentional impairments. Of pharmacological interventions, methylphenidate is recommended to improve information processing speed. Amantadine may facilitate arousal in comatose or vegetative patients but does not enhance performance on attentional measures over the longer term. The antioxidant Chinese herbal supplement MLC901 (NeuroAiD IITM) may enhance selective attention in individuals with mild-moderate TBI.

CONCLUSION

Evidence for interventions to improve attention after TBI is slowly growing. However, more controlled trials are needed, especially evaluating behavioral or nonpharmacological interventions for attention.

Electric Field Strength From Prefrontal Transcranial Direct Current Stimulation Determines Degree of Working Memory Response: A Potential Application of Reverse-Calculation Modeling?

BACKGROUND

Transcranial direct current stimulation (tDCS) for working memory is an enticing treatment, but there is mixed evidence to date.

OBJECTIVES

We tested the effects of electric field strength from uniform 2 mA dosing on working memory change from prestimulation to poststimulation. Second, we statistically evaluated a reverse-calculation method of individualizing tDCS dose and its effect on normalizing electric field at the cortex.

MATERIALS AND METHODS

We performed electric field modeling on a data set of 28 healthy older adults (15 women, mean age = 73.7, SD = 7.3) who received ten sessions of active 2 mA tDCS (N = 14) or sham tDCS (N = 14) applied over bilateral dorsolateral prefrontal cortices (DLPFC) in a triple-blind design. We evaluated the relationship between electric field strength and working memory change on an N-back task in conditions of above-median, high electric field from active 2 mA (N = 7), below-median, low electric field from active 2 mA (N = 7), and sham (N = 14) at regions of interest (ROI) at the left and right DLPFC. We then determined the individualized reverse-calculation dose to produce the group average electric field and measured the electric field variance between uniform 2 mA doses vs individualized reverse-calculation doses at the same ROIs.

RESULTS

Working memory improvements from pre- to post-tDCS were significant for the above-median electric field from active 2 mA condition at the left DLPFC (mixed ANOVA, p = 0.013). Furthermore, reverse-calculation modeling significantly reduced electric field variance at both ROIs (Levene's test; p < 0.001).

CONCLUSIONS

Higher electric fields at the left DLPFC from uniform 2 mA doses appear to drive working memory improvements from tDCS. Individualized doses from reverse-calculation modeling significantly reduce electric field variance at the cortex. Taken together, using reverse-calculation modeling to produce the same, high electric fields at the cortex across participants may produce more effective future tDCS treatments for working memory.

The Effectiveness of Non-Invasive Brain Stimulation Alone or Combined with Cognitive Training on the Cognitive Performance of Patients With Traumatic Brain Injury: Α Systematic Review

OBJECTIVE

The present study reviewed published evidence on the effectiveness of non-invasive brain stimulation (NIBS) on the cognitive performance of patients with Traumatic brain injury (TBI).

METHOD

A systematic search of the PubMed and Google Scholar databases was carried out. Randomized Controlled Studies published before March 2020 were included. Methodological evaluation was performed based on the Risk of Bias Cochrane tool. A total of 10 placebo-controlled studies fulfilled the inclusion criteria and were involved in the qualitative analysis, two assessing NIBS combined with cognitive training (CT) and eight evaluating NIBS alone.

RESULTS

All but one retrieved article were appraised as of high-risk of bias (one paper was assessed as of unclear-risk owing to considerable underreporting). With the potential exception of attention, our findings were not indicative of a superior efficacy of NIBS-CT to CT alone, regarding the improvement of any of the rest assessed cognitive deficits. Executive function, processing speed, attention, working, and visuospatial memory were only occasionally found to benefit from NIBS alone compared to sham therapy (only one study reported relevant benefits per neuropsychological outcome). Verbal memory and verbal fluency (phonemic-semantic) were consistently found not to benefit from NIBS. Depression measures were the only outcomes associated with a beneficial effect of NIBS in more than one article.

CONCLUSION

Our findings did not provide sufficient high-quality evidence to support the exclusive use of NIBS or combined NIBS-CT to improve any impaired cognitive function in TBI patients. Owing to the suboptimum methodological quality of published studies, additional research is of potential value.