Mood and cognitive effects of transcranial direct current stimulation in post-stroke depression

Transcranial direct current stimulation for the treatment of post-stroke depression: A systematic review

Background

Post-stroke depression (PSD) is not only a frequent neuropsychiatric manifestation secondary to stroke but is also associated with disability, poor rehabilitation outcomes, sleep disorders, cognitive impairment, and increased mortality. Transcranial direct current stimulation (tDCS), a primary modality of non-invasive brain stimulation (NIBS), has shown promising clinical results in the rehabilitation of patients with PSD recently. The primary aim of this systematic review is to assess the effects of tDCS on PSD.

Methods

PubMed and Cochrane databases were used for paper identification up to May 2022. Only English language studies and published data were taken into consideration. The methodological quality of selected studies was assessed according to the modified Sackett Scale, based on Physiotherapy Evidence Database (PEDro) scores.

Results

Six experimental studies were included for the PSD treatment of tDCS and all of them reported that, following the intervention of tDCS, the experimental group shows a statistically significant decrease in the depression level in accordance with different assessment scales.

Conclusion

This article simply aims at providing a comprehensive overview of the raw data reported in this field to date. Based on the current evidence, tDCS presents promising results for the treatment of PSD. Moreover, tDCS is also effective in PSD patients with aphasia or CPSP. However, an optimal stimulation protocol is needed to formulate. Thus, the development of robustly controlled, randomized, and high-quality clinical trials to further assess the utility of tDCS as a therapeutic tool for the treatment of PSD survivors is encouraged.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023322076, identifier: CRD42023322076.

A Narrative Review on the Non-Pharmacologic Interventions in Post-Stroke Depression

Stroke is a major cause of death and disability globally. Post-stroke depression (PSD) is a major driver for poor recovery and poor quality of life with extra burden for the patient and the caregiver. We have previously shown the inflammatory basis of PSD with associated bioenergetic failure, disruption of the blood-brain barrier, cell death, and persistent maladapted inflammation, making the PSD a norm rather than the exception, highlighting the unmet need for therapeutic intervention in PSD across the recovery trajectory. In this era, various interventions are focused on pharmacotherapy; however, non-pill-based medication should also be explored as post-stroke patients are likely to suffer from the adverse effects of polypharmacy. This narrated review explores the status of non-pharmacological interventions in managing PSD. We performed a PubMed search using pre-specified keywords looking at various non-pharmacologic approaches for the management of PSD. Worldwide, approaches such as non-invasive brain stimulation, behavioral and psychosocial therapy, as well as exercise, acupuncture, music, literature, and art therapies are available as monotherapy or adjunctive treatment for PSD. While current literature shows convincing results on the benefits of non-pharmacologic interventions, more robust studies are necessary to determine its utility in PSD.

Investigation of the effect of delayed auditory feedback and transcranial direct current stimulation (DAF-tDCS) treatment for the enhancement of speech fluency in adults who stutter: A randomized controlled trial

BACKGROUND

Stuttering is a disorder that begins in childhood and can persist into adulthood. In the present study, it was hypothesized that the combined intervention of transcranial direct current stimulation (tDCS) and Delayed Auditory Feedback (DAF) would cause greater improvement in speech fluency in comparison to the intervention with DAF alone.

METHODS

A randomized, double-blind, sham-controlled clinical trial was conducted to investigate the effects of the combined intervention. Fifty adults with moderate to severe stuttering (25 females, 25 males, Mean age=26.92, SD=6.23) were randomly allocated to the anodal or sham tDCS group. In the anodal tDCS group, participants received DAF combined with anodal tDCS (1 mA), while the sham tDCS group was exposed to sham tDCS simultaneously with DAF. In this study, a 60-ms delay was used for DAF intervention, and tDCS was applied over the left superior temporal gyrus. Each individual participated in six 20-minute intervention sessions (held on six consecutive days). Speech fluency was assessed before and after the intervention.

RESULTS

In the anodal tDCS group, the scores of the Stuttering Severity Instrument, Overall Assessment of the Speaker's Experience of Stuttering questionnaire, and the percentage of stuttered syllable reduced significantly (from average baseline rates of 8.45%, across three tasks, to 5.36% at the follow-up assessment) after the intervention.

CONCLUSION

The results of this study suggest that delivery of anodal tDCS when combined with DAF may enhance stuttering reduction effects for six weeks following the intervention.

Post-stroke depression: Chaos to exposition

Cerebral ischemia contributes to significant disabilities worldwide, impairing cognitive function and motor coordination in affected individuals. Stroke has severe neuropsychological outcomes, the major one being a stroke. Stroke survivors begin to show symptoms of depression within a few months of the incidence that overtime progresses to become a long-term ailment. As the pathophysiology for the progression of the disease is multifactorial and complex, it limits the understanding of the disease mechanism completely. Meta-analyses and randomized clinical trials have shown that intervening early with tricyclic antidepressants and selective serotonin receptor inhibitors can be effective. However, these pharmacotherapies possess several limitations that have given rise to newer approaches such as brain stimulation, psychotherapy and rehabilitation therapy, which in today's time are gaining attention for their beneficial results in post-stroke depression (PSD). The present review highlights numerous factors like lesion location, inflammatory mediators and genetic abnormalities that play a crucial role in the development of depression in stroke patients. Further, we have also discussed various mechanisms involved in post-stroke depression (PSD) and strategies for early detection and diagnosis using biomarkers that may revolutionize treatment for the affected population. Towards the end, along with the preclinical scenario, we have also discussed the various treatment approaches like pharmacotherapy, traditional medicines, psychotherapy, electrical stimulation and microRNAs being utilized for effectively managing PSD.

Comparison of Treatment Rates of Depression After Stroke Versus Myocardial Infarction: A Systematic Review and Meta-Analysis of Observational Data

OBJECTIVE

Depression after stroke and myocardial infarction (MI) is common but often assumed to be undertreated without reliable evidence being available. Thus, we aimed to determine treatment rates and investigate the application of guidelines in these conditions.

METHODS

Databases MEDLINE, EMBASE, PsycInfo, Web of Science, CINAHL, and Scopus were systematically searched without language restriction from inception to June 30, 2017. Prospective observational studies with consecutive recruitment reporting any antidepressant treatment in adults with depression after stroke or MI were included. Random-effects models were used to calculate pooled estimates of treatment rates.

RESULTS

Fifty-five studies reported 32 stroke cohorts (n = 8938; pooled frequency of depression = 34%, 95% confidence interval [CI] = 29%-38%) and 17 MI cohorts (n = 10,767; pooled frequency of depression = 24%, 95% CI = 20%-28%). In 29 stroke cohorts, 24% (95% CI = 20%-27%) of 2280 depressed people used antidepressant medication. In 15 MI cohorts, 14% (95% CI = 8%-19%) of 2381 depressed people used antidepressant medication indicating a lower treatment rate than in stroke. Two studies reported use of psychosocial interventions, indicating that less than 10% of participants were treated.

CONCLUSIONS

Despite the high frequency of depression after stroke and MI and the existence of efficacious treatment strategies, people often remain untreated. Innovative strategies are needed to increase the use of effective antidepressive interventions in patients with cardiovascular disease.

A systematic review of noninvasive brain stimulation for post-stroke depression

BACKGROUND

Post-stroke depression (PSD) is among the most frequent neuropsychiatric consequences of stroke, negatively affecting the patient's functional recovery and the quality of life. While pharmacological therapy has limited efficacy and important side effects, new appropriate treatments based on specific physiological mechanisms for PSD remain to be developed. Non-invasive brain stimulation (NIBS) techniques, modulating brain plasticity, might offer valid, alternative strategies.

METHODS

We systematically searched four databases: MEDLINE, PsycARTICLES, PsycINFO and Web of Science, up to December 2017, using definite keywords, to identify studies on TMS and tDCS treatment for PSD.

RESULTS

Seven studies met the inclusion criteria and the results indicate that both tDCS and rTMS are safe and have very low side effects. The reported positive results, suggesting that these methods can be considered effective therapeutic options, are questionable, and a general statement about their efficacy for PSD is premature due to small sample sizes, heterogeneous methodologies, lack of uniform diagnostic criteria, and divergent data.

LIMITATIONS

The selected articles suffer lack of information about quality of life and daily living performance measures; in addition, the number of randomized controlled trials is small.

CONCLUSION (S)

The aim of this review was to analyze current research in the clinical use of noninvasive brain stimulation (NIBS) in PSD treatment in order to verify whether there are alternative perspectives in the treatment of PSD. Given the present evidence, future research is needed to address methodological limitations and evaluate the long-term efficacy of these methods, alone and in combination with pharmacological treatment.

Transcranial Direct Current Stimulation (tDCS): A Promising Treatment for Major Depressive Disorder?

Background: Transcranial direct current stimulation (tDCS) opens new perspectives in the treatment of major depressive disorder (MDD), because of its ability to modulate cortical excitability and induce long-lasting effects. The aim of this review is to summarize the current status of knowledge regarding tDCS application in MDD. Methods: In this review, we searched for articles published in PubMed/MEDLINE from the earliest available date to February 2018 that explored clinical and cognitive effects of tDCS in MDD. Results: Despite differences in design and stimulation parameters, the examined studies indicated beneficial effects of tDCS for MDD. These preliminary results, the non-invasiveness of tDCS, and its good tolerability support the need for further research on this technique. Conclusions: tDCS constitutes a promising therapeutic alternative for patients with MDD, but its place in the therapeutic armamentarium remains to be determined.

Acute and repetitive fronto-cerebellar tDCS stimulation improves mood in non-depressed participants

Transcranial direct current stimulation (tDCS) is a non-invasive form of brain stimulation, which allows for selective inhibition or excitation of neural structures. It has demonstrated some efficacy in the treatment of mood disorders. However, these studies have predominately focused on stimulation of the prefrontal cortex (PFC). The cerebellum has an increasingly recognized role in emotional control, affective state, and some psychopathologies. As such, tDCS research into mood modulation needs to expand beyond conventional PFC-focused paradigms. Using a contralateral stimulation electrode placement [anodal left dorsolateral(dl)PFC, cathodal right cerebellum], and a single-blind, repeated-measures design, we initially assessed changes in the mood of healthy participants in response to acute stimulation (n = 44) and three repeated stimulations delivered second-daily (n = 21). In a second experiment, we separately investigated the influence of reversed polarity upon these same measures, in response to acute stimulation (n = 23) and repeated stimulation (n = 11). We observed a systematic elevation of mood in both active conditions following single and repeated tDCS, the latter of which displayed a progressive elevation of mood from baseline. No mood change was noted in response to either single or repeated stimulation in the sham condition. Frontocerebellar tDCS stimulation advantageously influences mood in healthy participants, with an accumulative and potentiated effect following successive stimulations. The possibility that frontocerebellar stimulation may provide a novel therapeutic adjunctive or pre-emptive intervention in stress-related disorders and mood-related psychopathologies should be considered.

Transcranial Direct Current Stimulation for Post-Concussion Syndrome: Study Protocol for a Randomized Crossover Trial

Background

Mild traumatic brain injury (MTBI) represents 70–80% of all treated brain injuries. A considerable proportion of MTBI patients experience post-concussion symptoms for a prolonged period after MTBI, and these symptoms are diagnosed as persistent post-concussion syndrome (PPCS). PPCS is defined as a range of physical, cognitive, and emotional symptoms. However, memory and executive dysfunction seems to be one of the most debilitating symptoms. Recently, non-invasive brain stimulation has been studied as a potential treatment method for traumatic brain injury (TBI) patients. Therefore, our primary goal is to verify the effects of transcranial direct current stimulation (tDCS) in patients with PPCS who demonstrate cognitive deficits in long-term episodic memory, working memory, and executive function following MTBI.

Methods/design

This is a randomized crossover trial of patients with a history of MTBI with cognitive deficits in memory and executive function. Thirty adult patients will be randomized in a crossover manner to receive three weekly sessions of anodal tDCS (2 mA) at left dorsolateral prefrontal cortex, left temporal cortex, and sham stimulation that will be performed at 7-day intervals (washout period). The clinical diagnosis of PPCS will be determined using the Rivermead Post-Concussion Symptoms Questionnaire. Patients who meet the inclusion criteria will be assessed with a neuropsychological evaluation. A new battery of computerized neuropsychological tests will be performed before and immediately after each stimulation. Statistical analysis will be performed to determine trends of cognitive improvement.

Discussion

There is paucity of studies regarding the use of tDCS in TBI patients, and although recent results showed controversial data regarding the effects of tDCS in such patients, we will address specifically patients with PPCS and MTBI and no brain abnormalities on CT scan other than subarachnoid hemorrhage. Moreover, due to the missing information on literature regarding the best brain region to be studied, we will evaluate two different regions to find immediate effects of tDCS on memory and executive dysfunction.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier NCT02292589 (https://register.clinicaltrials.gov).

Effect of transcranial direct current stimulation of stroke patients on depression and quality of life

[Purpose] The aim of this study was to assess the effects of transcranial direct current stimulation (tDCS) on depression and quality of life (QOL) in patients with stroke, by conducting conventional occupational therapy with and without tDCS on 20 patients each. [Subjects and Methods] The experimental group (N=20) received both tDCS and conventional occupational therapy, while the control group (N=20) received false tDCS and conventional occupational therapy. The treatment was conducted 20 times over a four-week period; each session was 30 minutes long. The Beck Depression Inventory (BDI) was administered to score the depression levels in patients before and after the intervention, while the stroke-specific quality of life (SS-QOL) was measured to compare the QOL. [Result] Following the intervention, the patients in the experimental group showed a significant decrease in depression and an increase in the QOL. In contrast, the control group showed no significant changes in depression or QOL. Our findings indicate that tDCS decreased depression while increasing QOL in patients with stroke. [Conclusion] In other words, our study confirmed that the application of tDCS during stroke rehabilitation improves the depression symptoms and QOL in patients.

Transcranial direct current stimulation for the treatment of post-stroke depression: results from a randomised, sham-controlled, double-blinded trial

BACKGROUND

Post-stroke depression is a disabling condition occurring in about one-third of patients with stroke. Pharmacological treatments have limited efficacy and important side effects. Recently, transcranial direct current stimulation (tDCS) has shown efficacy in treating depression. This study aimed to assess the efficacy and safety of tDCS for post-stroke depression.

METHODS

48 antidepressant-free patients with post-stroke depression were randomised into two groups (active and sham tDCS). 12 30 min sessions of 2 mA anodal left/cathodal right dorsolateral prefrontal tDCS were administered over 6 weeks (once daily on weekdays for 2 weeks, then 1 session every other week). The primary outcome was the change in the Hamilton Depression Rating Scale (17-items) at 6 weeks. We employed a repeated-measures analysis of variance; the depression score was the dependent variable, and time and group were independent variables. In this intention-to-treat analysis, missing data were addressed according to the last observation carried forward and the mixed-model repeated-measures analysis methods.

RESULTS

5 patients dropped out (two in the active group). Active tDCS was significantly superior to sham at end point (mean difference, 4.7 points; SD=9.21; p<0.001). Response and remission rates were significantly higher in the active (37.5% and 20.8%, respectively) versus the sham (4.1% and 0%, respectively) group, with a number-needed-to-treat of 3 and 5, respectively.

CONCLUSIONS

This was the first controlled study to demonstrate that tDCS was safe and effective for post-stroke depression. Therefore, tDCS might be a favourable option for treating these patients.

TRIAL REGISTRATION NUMBER

NCT01525524; Results.

Individual Differences and State-Dependent Responses in Transcranial Direct Current Stimulation

Transcranial direct current stimulation (tDCS) has been extensively used to examine whether neural activities can be selectively increased or decreased with manipulations of current polarity. Recently, the field has reevaluated the traditional anodal-increase and cathodal-decrease assumption due to the growing number of mixed findings that report the effects of the opposite directions. Therefore, the directionality of tDCS polarities and how it affects each individual still remain unclear. In this study, we used a visual working memory (VWM) paradigm and systematically manipulated tDCS polarities, types of different independent baseline measures, and task difficulty to investigate how these factors interact to determine the outcome effect of tDCS. We observed that only low-performers, as defined by their no-tDCS corsi block tapping (CBT) performance, persistently showed a decrement in VWM performance after anodal stimulation, whereas no tDCS effect was found when participants were divided by their performance in digit span. In addition, only the optimal level of task difficulty revealed any significant tDCS effect. All these findings were consistent across different blocks, suggesting that the tDCS effect was stable across a short period of time. Lastly, there was a high degree of intra-individual consistency in one’s responsiveness to tDCS, namely that participants who showed positive or negative effect to anodal stimulation are also more likely to show the same direction of effects for cathodal stimulation. Together, these findings imply that tDCS effect is interactive and state dependent: task difficulty and consistent individual differences modulate one’s responsiveness to tDCS, while researchers’ choices of independent behavioral baseline measures can also critically affect how the effect of tDCS is evaluated. These factors together are likely the key contributors to the wide range of “noises” in tDCS effects between individuals, between stimulation protocols, and between different studies in the literature. Future studies using tDCS, and possibly tACS, should take such state-dependent condition in tDCS responsiveness into account.

tDCS for the treatment of depression: a comprehensive review

Transcranial direct current stimulation (tDCS) has been investigated for the treatment of major depressive disorders in recent years. Here, we review the implications of current research for the clinical use of tDCS in the treatment of major depressive disorder. Meta-analyses, randomized, placebo-controlled clinical trials, open-label trials, case reports and review articles were identified through a systematic search of the literature database of the National Institutes of Health (USA). Available articles were evaluated with regard to their clinical relevance. Results of tDCS efficacy are inconsistent due to the small sample sizes, the heterogeneous patient samples and the partially high treatment resistance in some studies. Overall, tDCS has very low side effects. Meta-analyses suggest some efficacy of tDCS in the treatment of acute depressive disorder with moderate effect size, and low efficacy in treatment-resistant depression. A general statement about the efficacy of tDCS as a therapeutic tool in major depression seems to be premature. tDCS is considered as a safe therapeutic option and is associated with only minor side effects. The effectiveness of tDCS decreases with resistance to treatment. Psychotropic drugs may attenuate or amplify its effects. The use of 2 mA current strength over 20 min per day over a short time span can be considered as safe.

Evidence-based guidelines on the therapeutic use of transcranial direct current stimulation (tDCS)

A group of European experts was commissioned by the European Chapter of the International Federation of Clinical Neurophysiology to gather knowledge about the state of the art of the therapeutic use of transcranial direct current stimulation (tDCS) from studies published up until September 2016, regarding pain, Parkinson's disease, other movement disorders, motor stroke, poststroke aphasia, multiple sclerosis, epilepsy, consciousness disorders, Alzheimer's disease, tinnitus, depression, schizophrenia, and craving/addiction. The evidence-based analysis included only studies based on repeated tDCS sessions with sham tDCS control procedure; 25 patients or more having received active treatment was required for Class I, while a lower number of 10-24 patients was accepted for Class II studies. Current evidence does not allow making any recommendation of Level A (definite efficacy) for any indication. Level B recommendation (probable efficacy) is proposed for: (i) anodal tDCS of the left primary motor cortex (M1) (with right orbitofrontal cathode) in fibromyalgia; (ii) anodal tDCS of the left dorsolateral prefrontal cortex (DLPFC) (with right orbitofrontal cathode) in major depressive episode without drug resistance; (iii) anodal tDCS of the right DLPFC (with left DLPFC cathode) in addiction/craving. Level C recommendation (possible efficacy) is proposed for anodal tDCS of the left M1 (or contralateral to pain side, with right orbitofrontal cathode) in chronic lower limb neuropathic pain secondary to spinal cord lesion. Conversely, Level B recommendation (probable inefficacy) is conferred on the absence of clinical effects of: (i) anodal tDCS of the left temporal cortex (with right orbitofrontal cathode) in tinnitus; (ii) anodal tDCS of the left DLPFC (with right orbitofrontal cathode) in drug-resistant major depressive episode. It remains to be clarified whether the probable or possible therapeutic effects of tDCS are clinically meaningful and how to optimally perform tDCS in a therapeutic setting. In addition, the easy management and low cost of tDCS devices allow at home use by the patient, but this might raise ethical and legal concerns with regard to potential misuse or overuse. We must be careful to avoid inappropriate applications of this technique by ensuring rigorous training of the professionals and education of the patients.

Cognitive effects of transcranial direct current stimulation in depression: Results from the SELECT-TDCS trial and insights for further clinical trials

BACKGROUND

Cognitive dysfunction treatment remains an unmet clinical need in major depressive disorder (MDD). Transcranial direct current stimulation (tDCS) may improve cognitive symptoms in MDD. Our aim was to investigate the cognitive effects of tDCS in the Sertraline vs. Electric Current Therapy for Treating Depression Clinical Study (SELECT-TDCS). We also explored whether tDCS could have mood-independent cognitive effects.

METHODS

One hundred twenty MDD patients aged from 18 to 65 years received 12 sessions of active/sham tDCS (2mA for 30min) and real/placebo 50mg/d sertraline over 6 weeks in a factorial trial. We analyzed whether changes in performance of neuropsychological tests (Trail Making, Digit Span, Stroop Task, Mini-Mental Status Exam and Montreal Cognitive Assessment) occurred over time, according to treatment group and depression improvement. Exploratory analyses were carried out to verify the influence of clinical and demographic variables on the outcomes.

RESULTS

Cognitive improvement was showed in most tests used, although they occurred regardless of intervention type and depression improvement. Further exploratory analyses revealed that clinical response and education level could have mediated pro-cognitive tDCS effects on some of the tests used.

LIMITATIONS

The neuropsychological battery used might not have been sensitive to detect tDCS-induced effects on cognition. Lack of simultaneous cognitive training during application may have also limited its cognitive effects.

CONCLUSIONS

We found no evidence of beneficial or deleterious cognitive effects of tDCS as a treatment for depression. We discussed clinical trial design considerations for further tDCS studies assessing cognitive effects, including sample and outcomes considerations.

Systematic Review of Cognitive Effects of Electroconvulsive Therapy in Late-Life Depression

OBJECTIVE

Late-life depression (LLD) is known to negatively impact cognition even after remission of mood symptoms. Electroconvulsive therapy (ECT) and newer nonconvulsive electrical and magnetic brain stimulation interventions have been shown to have cognitive effects in patients with neuropsychiatric disorders.

METHODS

This review systematically assessed the effects of ECT on cognition in LLD. EMBASE, Ovid Medline, and PsycINFO were systematically searched through June 2015. The search was limited to publications from peer-reviewed journals in the English language.

RESULTS

A total of 5,154 publications was identified; 318 were reviewed in full text, of which 39 publications related to ECT were included. We focused this review only on ECT because evidence on newer interventions was deemed insufficient for a systematic review. This literature suggests increased rates of interictal and postictal cognitive decline with ECT but no long-term (i.e., 6 months or longer) deleterious effects on cognition. Instead, long-term cognitive outcomes with ECT have been reported as either not changed or improved. This literature favors nondominant unilateral ECT over bilateral ECT for cognition.

CONCLUSION

Published literature on brain stimulation interventions in LLD is mainly limited to ECT. This literature suggests that deleterious effects of ECT in LLD are limited and transient, with better cognitive outcomes with unilateral ECT. There is not enough evidence to fully characterize long-term deleterious effects of ECT or effects of newer brain stimulation techniques on cognition in LLD.

Neuropsychiatric sequelae of stroke

Stroke survivors are often affected by psychological distress and neuropsychiatric disturbances. About one-third of stroke survivors experience depression, anxiety or apathy, which are the most common neuropsychiatric sequelae of stroke. Neuropsychiatric sequelae are disabling, and can have a negative influence on recovery, reduce quality of life and lead to exhaustion of the caregiver. Despite the availability of screening instruments and effective treatments, neuropsychiatric disturbances attributed to stroke are currently underdiagnosed and undertreated. Stroke severity, stroke-related disabilities, cerebral small vessel disease, previous psychiatric disease, poor coping strategies and unfavourable psychosocial environment influence the presence and severity of the psychiatric sequelae of stroke. Although consistent associations between psychiatric disturbances and specific stroke locations have yet to be confirmed, functional MRI studies are beginning to unveil the anatomical networks that are disrupted in stroke-associated psychiatric disorders. Evidence regarding biochemical and genetic biomarkers for stroke-associated psychiatric disorders is still limited, and better understanding of the biological determinants and pathophysiology of these disorders is needed. Investigation into the management of these conditions must be continued, and should include pilot studies to assess the benefits of innovative behavioural interventions and large-scale cooperative randomized controlled pharmacological trials of drugs that are safe to use in patients with stroke.

Transcranial Electrical Stimulation in Post-Stroke Cognitive Rehabilitation

Abstract. Cognitive rehabilitation is an important area of neurological rehabilitation, which aims at the treatment of cognitive disorders due to acquired brain damage of different etiology, including stroke. Although the importance of cognitive rehabilitation for stroke survivors is well recognized, available cognitive treatments for neuropsychological disorders, such as spatial neglect, hemianopia, apraxia, and working memory, are overall still unsatisfactory. The growing body of evidence supporting the potential of the transcranial Electrical Stimulation (tES) as tool for interacting with neuroplasticity in the human brain, in turn for enhancing perceptual and cognitive functions, has obvious implications for the translation of this noninvasive brain stimulation technique into clinical settings, in particular for the development of tES as adjuvant tool for cognitive rehabilitation. The present review aims at presenting the current state of art concerning the use of tES for the improvement of post-stroke visual and cognitive deficits (except for aphasia and memory disorders), showing the therapeutic promises of this technique and offering some suggestions for the design of future clinical trials. Although this line of research is still in infancy, as compared to the progresses made in the last years in other neurorehabilitation domains, current findings appear very encouraging, supporting the development of tES for the treatment of post-stroke cognitive impairments.

Transcranial direct current stimulation for the treatment of post-stroke depression in aphasic patients: a case series

Aphasia is a common consequence of stroke; it is estimated that about two-thirds of aphasic patients will develop depression in the first year after the stroke. Treatment of post-stroke depression (PSD) is challenging due to the adverse effects of pharmacotherapy and difficulties in evaluating clinical outcomes, including aphasia. Transcranial direct current stimulation (tDCS) is a novel treatment that may improve clinical outcomes in the traditionally pharmacotherapy-refractory PSD. Our aim was to evaluate the safety and efficacy of tDCS for patients with PSD and with aphasia. The Stroke Aphasic Depression Questionnaire (SADQ) and the Aphasic Depression Rating Scale (ADRS) were used to evaluate the severity of PSD. The diagnoses of PSD and aphasia were confirmed by a psychiatrist and a speech-language pathologist, respectively. In this open case series, patients (n = 4) received 10 sessions (once a day) of bilateral tDCS to the dorsolateral prefrontal cortex (DLPFC) and two additional sessions after two and four weeks, for a total of 12 sessions. All patients exhibited improvement in depression after tDCS, as indicated by a decrease in SADQ (47.5%) and in ADRS (65.7%). This improvement was maintained four weeks after the treatment. In this preliminary, open-label study conducted in four PSD patients with aphasia, bilateral tDCS over the DLPFC was shown to induce a substantial mood improvement; tDCS was safe and well tolerated by every patient. Stroke patients with aphasia can be safely treated for PSD with tDCS. Sham-controlled studies are necessary to evaluate this technique further.

[Transcranial direct current stimulation (tDCS) for depression: Results of nearly a decade of clinical research]

OBJECTIVE

Since 2006 transcranial direct current stimulation (tDCS) has been investigated in the treatment of depression. In this review, we discuss the implications and clinical perspectives that tDCS may have as a therapeutic tool in depression from the results reported in this domain.

METHODS

A comprehensive literature review has found nearly thirty articles - all in English - on this topic, corresponding to clinical studies, placebo-controlled or not, case reports and reviews.

RESULTS

Several meta-analyses showed that the antidepressant effects of active tDCS are significant against placebo, but variable, mainly due to the heterogeneity of the patients included in the studies, for example regarding the resistance to antidepressant treatment.

CONCLUSIONS

Specific recommendations for the use of tDCS in treating depression may not yet be available, but some elements of good practice can be highlighted. Of particular note is that anodal tDCS of the left prefrontal cortex at 2mA for 20 minutes per day has a potential therapeutic value without risk of significant side effects: tDCS offers safe conditions for clinical use in the treatment of depression.

Executive function and depressive symptoms of retardation in nonelderly stroke patients

The depression-executive dysfunction syndrome, a late-onset depression of vascular origin with executive dysfunction and psychomotor retardation, has also been described after stroke. We verified whether this syndrome also occurs in nonelderly stroke patients by investigating the association between domains of depressive symptoms with executive functions in 87 first-ever ischemic stroke patients. The retardation domain of the 31-item Hamilton Rating Scale for Depression was associated with decreased performance on verbal fluency (assessed with FAS). The association was maintained for younger patients (aged <60 years) after adjusting for confounders. This result supports the clinical presentation of depression-executive dysfunction syndrome in younger stroke patients. Confirmation of this finding, its neural correlates, and clinical implication deserve further investigation.

Transcranial direct current stimulation and repetitive transcranial magnetic stimulation in consultation-liaison psychiatry

Patients with clinical diseases often present psychiatric conditions whose pharmacological treatment is hampered due to hazardous interactions with the clinical treatment and/or disease. This is particularly relevant for major depressive disorder, the most common psychiatric disorder in the general hospital. In this context, nonpharmacological interventions could be useful therapies; and, among those, noninvasive brain stimulation (NIBS) might be an interesting option. The main methods of NIBS are repetitive transcranial magnetic stimulation (rTMS), which was recently approved as a nonresearch treatment for some psychiatric conditions, and transcranial direct current stimulation (tDCS), a technique that is currently limited to research scenarios but has shown promising results. Therefore, our aim was to review the main medical conditions associated with high depression rates, the main obstacles for depression treatment, and whether these therapies could be a useful intervention for such conditions. We found that depression is an important and prevalent comorbidity in a variety of diseases such as epilepsy, stroke, Parkinson's disease, myocardial infarction, cancer, and in other conditions such as pregnancy and in patients without enteral access. We found that treatment of depression is often suboptimal within the above contexts and that rTMS and tDCS therapies have been insufficiently appraised. We discuss whether rTMS and tDCS could have a significant impact in treating depression that develops within a clinical context, considering its unique characteristics such as the absence of pharmacological interactions, the use of a nonenteral route, and as an augmentation therapy for antidepressants.

Targeted therapies using electrical and magnetic neural stimulation for the treatment of chronic pain in spinal cord injury

BACKGROUND

Chronic neuropathic pain is one of the most common and disabling symptoms in individuals with spinal cord injury (SCI). Over two-thirds of subjects with SCI suffer from chronic pain influencing quality of life, rehabilitation, and recovery. Given the refractoriness of chronic pain to most pharmacological treatments, the majority of individuals with SCI report worsening of this condition over time. Moreover, only 4-6% of patients in this cohort report improvement. Novel treatments targeting mechanisms associated with pain-maladaptive plasticity, such as electromagnetic neural stimulation, may be desirable to improve outcomes. To date, few, small clinical trials have assessed the effects of invasive and noninvasive nervous system stimulation on pain after SCI.

OBJECTIVE

We aimed to review initial efficacy, safety and potential predictors of response by assessing the effects of neural stimulation techniques to treat SCI pain.

SEARCH STRATEGY

A literature search was performed using the PubMed database including studies using the following targeted stimulation strategies: transcranial Direct Current Stimulation (tDCS), High Definition tDCS (HD-tDCS), repetitive Transcranial Magnetical Stimulation (rTMS), Cranial Electrotherapy Stimulation (CES), Transcutaneous Electrical Nerve Stimulation (TENS), Spinal Cord Stimulation (SCS) and Motor Cortex Stimulation (MCS), published prior to June of 2012. We included studies from 1998 to 2012.

RESULTS

Eight clinical trials and one naturalistic observational study (nine studies in total) met the inclusion criteria. Among the clinical trials, three studies assessed the effects of tDCS, two of CES, two of rTMS and one of TENS. The naturalistic study investigated the analgesic effects of SCS. No clinical trials for epidural motor cortex stimulation (MCS) or HD-tDCS were found. Parameters of stimulation and also clinical characteristics varied significantly across studies. Three out of eight studies showed larger effects sizes (0.73, 0.88 and 1.86 respectively) for pain reduction. Classical neuropathic pain symptoms such as dysesthesia (defined as an unpleasant burning sensation in response to touch), allodynia (pain due to a non-painful stimulus), pain in paroxysms, location of SCI in thoracic and lumbar segments and pain in the lower limbs seem to be associated with a positive response to neural stimulation. No significant adverse effects were reported in these studies.

CONCLUSIONS

Chronic pain in SCI is disabling and resistant to common pharmacologic approaches. Electrical and magnetic neural stimulation techniques have been developed to offer a potential tool in the management of these patients. Although some of these techniques are associated with large standardized mean differences to reduce pain, we found an important variability in these results across studies. There is a clear need for the development of methods to decrease treatment variability and increase response to neural stimulation for pain treatment. We discuss potential methods such as neuroimaging or EEG-guided neural stimulation and the development of better surrogate markers of response such as TMS-indexed cortical plasticity.

Partially non-linear stimulation intensity-dependent effects of direct current stimulation on motor cortex excitability in humans

Transcranial direct current stimulation (tDCS) of the human motor cortex at an intensity of 1 mA with an electrode size of 35 cm(2) has been shown to induce shifts of cortical excitability during and after stimulation. These shifts are polarity-specific with cathodal tDCS resulting in a decrease and anodal stimulation in an increase of cortical excitability. In clinical and cognitive studies, stronger stimulation intensities are used frequently, but their physiological effects on cortical excitability have not yet been explored. Therefore, here we aimed to explore the effects of 2 mA tDCS on cortical excitability. We applied 2 mA anodal or cathodal tDCS for 20 min on the left primary motor cortex of 14 healthy subjects. Cathodal tDCS at 1 mA and sham tDCS for 20 min was administered as control session in nine and eight healthy subjects, respectively. Motor cortical excitability was monitored by transcranial magnetic stimulation (TMS)-elicited motor-evoked potentials (MEPs) from the right first dorsal interosseous muscle. Global corticospinal excitability was explored via single TMS pulse-elicited MEP amplitudes, and motor thresholds. Intracortical effects of stimulation were obtained by cortical silent period (CSP), short latency intracortical inhibition (SICI) and facilitation (ICF), and I wave facilitation. The above-mentioned protocols were recorded both before and immediately after tDCS in randomized order. Additionally, single-pulse MEPs, motor thresholds, SICI and ICF were recorded every 30 min up to 2 h after stimulation end, evening of the same day, next morning, next noon and next evening. Anodal as well as cathodal tDCS at 2 mA resulted in a significant increase of MEP amplitudes, whereas 1 mA cathodal tDCS decreased corticospinal excitability. A significant shift of SICI and ICF towards excitability enhancement after both 2 mA cathodal and anodal tDCS was observed. At 1 mA, cathodal tDCS reduced single-pulse TMS-elicited MEP amplitudes and shifted SICI and ICF towards inhibition. No significant changes were observed in the other protocols. Sham tDCS did not induce significant MEP alterations. These results suggest that an enhancement of tDCS intensity does not necessarily increase efficacy of stimulation, but might also shift the direction of excitability alterations. This should be taken into account for applications of the stimulation technique using different intensities and durations in order to achieve stronger or longer lasting after-effects.

Continuation transcranial direct current stimulation for the prevention of relapse in major depression

BACKGROUND

Transcranial direct current stimulation (tDCS) is gaining attention as an effective new treatment for major depression. Little is known, however, of the duration of antidepressant effects following acute treatment. In this study, we describe the use of continuation tDCS treatment for up to 6 months following clinical response to an acute treatment course.

METHODS

Twenty-six participants pooled from two different studies involving different tDCS protocols received continuation tDCS treatment on a weekly basis for 3 months and then once per fortnight for the final 3 months. Mood ratings were completed at 3 and 6 months. Analyses examined clinical predictors of relapse during continuation tDCS treatment.

RESULTS

The cumulative probability of surviving without relapse was 83.7% at 3 months and 51.1% at 6 months. Medication resistance was found to be a predictor of relapse during continuation tDCS.

LIMITATIONS

This was an open label prospective study with no control group. Two different forms of tDCS were used.

CONCLUSION

Similar to other antidepressant treatments, continuation tDCS appears to be a useful strategy to prevent relapse following clinical response. These preliminary data suggest that the majority of patients maintained antidepressant benefit with a continuation schedule of at least weekly treatment. Future controlled studies are required to confirm these findings.

Transcranial direct current stimulation for the treatment of major depressive disorder: a summary of preclinical, clinical and translational findings

Major depressive disorder (MDD) is a common psychiatric illness, with 6-12% lifetime prevalence. It is also among the five most disabling diseases worldwide. Current pharmacological treatments, although relatively effective, present important side effects that lead to treatment discontinuation. Therefore, novel treatment options for MDD are needed. Here, we discuss the recent advancements of one new neuromodulatory technique--transcranial direct current stimulation (tDCS)--that has undergone intensive research over the past decade with promising results. tDCS is based on the application of weak, direct electric current over the scalp, leading to cortical hypo- or hyper-polarization according to the specified parameters. Recent studies have shown that tDCS is able to induce potent changes in cortical excitability as well as to elicit long-lasting changes in brain activity. Moreover, tDCS is a technique with a low rate of reported side effects, relatively easy to apply and less expensive than other neuromodulatory techniques--appealing characteristics for clinical use. In the past years, 4 of 6 phase II clinical trials and one recent meta-analysis have shown positive results in ameliorating depression symptoms. tDCS has some interesting, unique aspects such as noninvasiveness and low rate of adverse effects, being a putative substitutive/augmentative agent for antidepressant drugs, and low-cost and portability, making it suitable for use in clinical practice. Still, further phase II and phase III trials are needed as to better clarify tDCS role in the therapeutic arsenal of MDD.

Association among depression, cognitive impairment and executive dysfunction after stroke

The relationship between depression and cognitive impairment, frequent after stroke, is complex and has not been sufficiently elucidated.

Noninvasive brain stimulation to modulate neuroplasticity in traumatic brain injury

OBJECTIVE

To review the use of noninvasive brain stimulation (NBS) as a therapeutic tool to enhance neuroplasticity following traumatic brain injury (TBI).

MATERIALS AND METHODS

Based on a literature search, we describe the pathophysiological events following TBI and the rationale for the use of transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) in this setting.

RESULTS

The pathophysiological mechanisms occurring after TBI vary across time and therefore require differential interventions. Theoretically, given the neurophysiological effects of both TMS and tDCS, these tools may: 1) decrease cortical hyperexcitability acutely after TBI; 2) modulate long-term synaptic plasticity as to avoid maladaptive consequences; and 3) combined with physical and behavioral therapy, facilitate cortical reorganization and consolidation of learning in specific neural networks. All of these interventions may help decrease the burden of disabling sequelae after brain injury.

CONCLUSIONS

Evidence from animal and human studies reveals the potential benefit of NBS in decreasing the extent of injury and enhancing plastic changes to facilitate learning and recovery of function in lesioned neural tissue. However, this evidence is mainly theoretical at this point. Given safety constraints, studies in TBI patients are necessary to address the role of NBS in this condition as well as to further elucidate its therapeutic effects and define optimal stimulation parameters.

Parietal contributions to visual working memory depend on task difficulty

The nature of parietal contributions to working memory (WM) remain poorly understood but of considerable interest. We previously reported that posterior parietal damage selectively impaired WM probed by recognition (Berryhill and Olson, 2008a). Recent studies provided support using a neuromodulatory technique, transcranial direct current stimulation (tDCS) applied to the right parietal cortex (P4). These studies confirmed parietal involvement in WM because parietal tDCS altered WM performance: anodal current tDCS improved performance in a change detection task, and cathodal current tDCS impaired performance on a sequential presentation task. Here, we tested whether these complementary results were due to different degrees of parietal involvement as a function of WM task demands, WM task difficulty, and/or participants' WM capacity. In Experiment 1, we applied cathodal and anodal tDCS to the right parietal cortex and tested participants on both previously used WM tasks. We observed an interaction between tDCS (anodal, cathodal), WM task difficulty, and participants' WM capacity. When the WM task was difficult, parietal stimulation (anodal or cathodal) improved WM performance selectively in participants with high WM capacity. In the low WM capacity group, parietal stimulation (anodal or cathodal) impaired WM performance. These nearly equal and opposite effects were only observed when the WM task was challenging, as in the change detection task. Experiment 2 probed the interplay of WM task difficulty and WM capacity in a parametric manner by varying set size in the WM change detection task. Here, the effect of parietal stimulation (anodal or cathodal) on the high WM capacity group followed a linear function as WM task difficulty increased with set size. The low WM capacity participants were largely unaffected by tDCS. These findings provide evidence that parietal involvement in WM performance depends on both WM capacity and WM task demands. We discuss these findings in terms of alternative WM strategies employed by low and high WM capacity individuals. We speculate that low WM capacity individuals do not recruit the posterior parietal lobe for WM tasks as efficiently as high WM capacity individuals. Consequently, tDCS provides greater benefit to individuals with high WM capacity.

The emerging use of brain stimulation treatments for psychiatric disorders

OBJECTIVE

The aim of this study was to review the current state of development and application of a wide range of brain stimulation approaches in the treatment of psychiatric disorders.

METHOD

The approaches reviewed include forms of minimally invasive magnetic and electrical stimulation, seizure induction, implanted devices and several highly novel approaches in early development.

RESULTS

An extensive range of brain stimulation approaches are now being widely used in the treatment of patients with psychiatric disorders, or actively investigated for this use. Both vagal nerve stimulation (VNS) and repetitive transcranial magnetic stimulation (rTMS) have been introduced into clinical practice in some countries. A small body of research suggests that VNS has some potentially long-lasting antidepressant effects in a minority of patients treated. rTMS has now been extensively investigated for over 15 years, with a large body of research now supporting its antidepressant effects. Further rTMS research needs to focus on defining the most appropriate stimulation methods and exploring its longer term use in maintenance protocols. Very early data suggest that magnetic seizure therapy (MST) has promise in the treatment of patients referred for electroconvulsive therapy: MST appears to have fewer side effects and may have similar efficacy. A number of other approaches including surgical and alternative forms of electrical stimulation appear to alter brain activity in a promising manner, but are in need of evaluation in more substantive patient samples.

CONCLUSIONS

It appears likely that the range of psychiatric treatments available for patients will grow over the coming years to progressively include a number of novel brain stimulation techniques.

Treatment of late-life depression: a role of non-invasive brain stimulation techniques

Late-life depression (LLD) is a frequent complication of the ageing process, occurring in up to 5% of community-dwelling elderly and in a higher proportion of subjects with coexistent medical illnesses. Its presence has been consistently associated with cognitive impairment, greater disability and increased mortality. Approximately half of patients with LLD have evidence of subcortical ischaemic damage in prefrontal circuits revealed by MRI. This might constitute the biological substrate of the cardinal symptoms of depression and of executive dysfunction. An important proportion of patients with LLD do not achieve remission of their depressive symptoms in spite of adequate pharmacological and psychotherapeutic treatment. In addition, a group of LLD patients progress to further impairment and disability in the form of a dementing disorder. There is an imperative need to develop new treatment strategies for LLD. Non-invasive brain stimulation techniques such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) are safe and efficacious interventions that might be used in combination with other therapeutic options to improve treatment outcomes. However, there are still questions regarding the optimal way in which rTMS and dTCS should be delivered as well as to the way in which we may identify the subjects who will benefit the most from these interventions.