The neurorehabilitation of post-stroke dysphagia: Physiology and pathophysiology

Swallowing is a complex process involving the precise contractions of numerous muscles of the head and neck, which act to process and shepherd ingested material from the oral cavity to its eventual destination, the stomach. Over the past five decades, information from animal and human studies has laid bare the complex network of neurones in the brainstem, cortex and cerebellum that are responsible for orchestrating each normal swallow. Amidst this complexity, problems can and often do occur that result in dysphagia, defined as impaired or disordered swallowing. Dysphagia is common, arising from multiple varied disease processes that can affect any of the neuromuscular structures involved in swallowing. Post-stroke dysphagia (PSD) remains the most prevalent and most commonly studied form of dysphagia and, as such, provides an important disease model to assess dysphagia physiology and pathophysiology. In this review, we explore the complex neuroanatomical processes that occur during normal swallowing and PSD. This includes how strokes cause dysphagia, the mechanisms through which natural neuroplastic recovery occurs, current treatments for patients with persistent dysphagia and emerging neuromodulatory treatments.

Contrasting MEG effects of anodal and cathodal high-definition TDCS on sensorimotor activity during voluntary finger movements

Introduction

Protocols for noninvasive brain stimulation (NIBS) are generally categorized as "excitatory" or "inhibitory" based on their ability to produce short-term modulation of motor-evoked potentials (MEPs) in peripheral muscles, when applied to motor cortex. Anodal and cathodal stimulation are widely considered excitatory and inhibitory, respectively, on this basis. However, it is poorly understood whether such polarity-dependent changes apply for neural signals generated during task performance, at rest, or in response to sensory stimulation.

Methods

To characterize such changes, we measured spontaneous and movement-related neural activity with magnetoencephalography (MEG) before and after high-definition transcranial direct-current stimulation (HD-TDCS) of the left motor cortex (M1), while participants performed simple finger movements with the left and right hands.

Results

Anodal HD-TDCS (excitatory) decreased the movement-related cortical fields (MRCF) localized to left M1 during contralateral right finger movements while cathodal HD-TDCS (inhibitory), increased them. In contrast, oscillatory signatures of voluntary motor output were not differentially affected by the two stimulation protocols, and tended to decrease in magnitude over the course of the experiment regardless. Spontaneous resting state oscillations were not affected either.

Discussion

MRCFs are thought to reflect reafferent proprioceptive input to motor cortex following movements. Thus, these results suggest that processing of incoming sensory information may be affected by TDCS in a polarity-dependent manner that is opposite that seen for MEPs-increases in cortical excitability as defined by MEPs may correspond to reduced responses to afferent input, and vice-versa.

Cathodal HD-tDCS and attention: A study on patients with intractable left lateral frontal lobe epilepsy

OBJECTIVE

Defects in the attentional network in patients with epilepsy are influenced by factors such as the location of epileptic foci. Examining the impact of cathodal high-definition transcranial direct current stimulation (HD-tDCS) on attention components could provide insights into potential attention-related side effects of tDCS. This study aimed to investigate the effect of cathodal HD-tDCS on interictal epileptiform discharges (IEDs), auditory/visual (A/V) attention components, and reaction time (RT) in patients with intractable focal left lateral frontal lobe epilepsy (LFLE).

METHODS

To control for variations in individual epilepsy syndrome, 12 adult participants diagnosed with drug-resistant left LFLE with focal cortical IEDs on C3 underwent repeated measurements at pretest, posttest, and follow-up steps. 4 × 1 ring electrodes (cathode on C3 and four anodes on F3, P3, T3, and Cz) delivered 2 mA DC for 20 min per session for 10 consecutive days. The integrated visual and auditory continuous performance test (IVA+) assessed the A/V attention components and RT. One-way repeated-measure ANOVA was used.

RESULTS

The findings suggest a significant effect in reducing IEDs. The IVA+ results showed a significant improvement in auditory divided attention and visual selective and focused attention (p < 0.05). In the follow-up, these changes demonstrated lasting efficacy. A/V speed scales increased (p < 0.05), showing a significant decrease in reaction time.

CONCLUSIONS

Cathodal HD-tDCS significantly reduced IEDs and improved the components of auditory divided attention, visual focused attention, and visual selective attention, with a reduction in patient reaction time. A significant lasting, side-effect-free positive effect was observed for up to one month after the intervention.

The effects of left prefrontal stimulation on selective attention and emotional reactivity for positive and negative information

Transcranial direct current stimulation targeting lateral prefrontal areas may attenuate attentional vigilance for negative content and reduce emotional reactivity. However, little research to date has examined how such stimulation may affect attention towards and emotional reactivity to positive emotional content. The aim of this study was to examine whether anodal tDCS targeting the left dorsolateral prefrontal cortex would affect attentional bias towards either or both negative and positive content, and similarly, how it would impact emotional reactivity to negative and positive emotional content among healthy individuals. Unselected participants (N = 101) were recruited (Mage = 22.57, SD = 5.60; 66.33% female) and allocated to either an active or sham tDCS condition. Attentional bias was measured using an eye-tracking task involving negative-neutral and positive-neutral image pairs, followed by an emotional reactivity assessment task involving negative and positive video content (self-report and heart rate variability). Results showed no evidence that tDCS influenced attentional patterns towards either positive or negative information, nor was there evidence that tDCS influenced self-reported anxious mood or physiological arousal. However, participants in the active tDCS condition reported higher positive mood in response to both the positive and negative videos compared to those in the sham condition and also higher arousal in response to positive content and lower arousal in response to negative content, with those in the sham tDCS condition showing the reverse pattern of effects. As such, tDCS effects on emotional reactivity to positive and negative content were restricted to self-report measures.

A century of research on neuromodulation interventions: A scientometric analysis of trends and knowledge maps

Interest in neurostimulation interventions has significantly grown in recent decades, yet a scientometric analysis objectively mapping scientific knowledge and recent trends remains unpublished. Using relevant keywords, we conducted a search in the Web of Science Core Collection on September 23, 2022, retrieving a total of 47,681 documents with 987,979 references. We identified two prominent research trends: 'noninvasive brain stimulation' and 'invasive brain stimulation.' These methods have interconnected over time, forming a cluster focused on evidence synthesis. Noteworthy emerging research trends encompassed 'transcutaneous auricular vagus nerve stimulation,' 'DBS/epilepsy in the pediatric population,' 'spinal cord stimulation,' and 'brain-machine interface.' While progress has been made for various neurostimulation interventions, their approval as adjuvant treatments remains limited, and optimal stimulation parameters lack consensus. Enhancing communication between experts of both neurostimulation types and encouraging novel translational research could foster further development. These findings offer valuable insights for funding agencies and research groups, guiding future directions in the field.

Effects of transcranial electrical stimulation techniques on foreign vocabulary learning

Although the use of transcranial electrical stimulation (tES) techniques on healthy population has been linked to facilitating language learning, studies on their effects on foreign language learning processes are scarce and results remain unclear. The objective of this study was to analyze whether tES enhances foreign language learning processes. Sixty-four healthy native Spanish-speaking participants were randomly assigned to four groups (transcranial direct current, transcranial random noise, tDCS-tRNS stimulation, or sham). They completed two intervention sessions with a two-week gap in between. During the first session the participants received stimulation (1.5 mA) while learning new English words and then performed recall and recognition tasks. Learning was assessed at follow-up, two weeks later. No differences in learning between groups were observed in the first session (F_(1,61)= .86; p = .36). At follow-up, significantly higher learning accuracy was observed after tRNS compared to sham (p = .037). These results suggest that tRNS could be helpful in improving the processes involved in foreign language vocabulary learning.

Use of the P300 event-related potential component to index transcranial direct current stimulation effects in drug users

Drug use causes significant social and financial problems and these are exacerbated by difficulties in stopping use and subsequent maintenance of abstinence. There is also difficulty in identifying the beneficial treatment for an individual, made more problematic given the high drop-out rates in treatment programs. Here, the effects of transcranial direct current stimulation (tDCS) on the amplitude of the P300 event-related potential component, previously suggested to be indicative of successful remission, was measured in recently abstinent amphetamine users. This component was collected during a Posner cuing task which was presented to this group and to control (non-user) participants, using task cues of neutral and drug-related images. The abstinent drug users were divided into two groups, one of which received tDCS daily for five days, with the cathode over the left dorsolateral prefrontal cortex (DLPFC) and the anode over the right DLPFC, and one receiving sham stimulation over the same time period. Behavioral performance and P300 amplitudes were measured before and after the period of tDCS delivery. Control participants were tested with the same time-schedule of task presentation but without administration of tDCS. Drug users initially showed a larger cost of invalid cues on task performance compared to control (non-drug user) participants and this was reduced following delivery of tDCS. Additionally, tDCS resulted in increased amplitude of the P300 component, significantly so for neutral cues, with the resulting pattern being more similar to that of the non-users. This provides a good basis for further investigation of both the utility of tDCS in modulation of cognition in addict groups, and to investigate the effects of modulating the P300 component on remission rates, a relationship that seems to be the case for this measure without use of tDCS modulation. Importantly, this study also provides a further addiction group showing P300 amplitude modulation as a result of tDCS administration.

Repetitive Anodal TDCS to the Frontal Cortex Increases the P300 during Working Memory Processing

Transcranial direct current stimulation (TDCS) is a technique with which neuronal activity, and therefore potentially behavior, is modulated by applying weak electrical currents to the scalp. Application of TDCS to enhance working memory (WM) has shown promising but also contradictory results, and little emphasis has been placed on repeated stimulation protocols, in which effects are expected to be increased. We aimed to characterize potential behavioral and electrophysiological changes induced by TDCS during WM training and evaluate whether repetitive anodal TDCS has a greater modulatory impact on the processes underpinning WM than single-session stimulation. We examined the effects of single-session and repetitive anodal TDCS to the dorsolateral prefrontal cortex (DLPFC), targeting the frontal-parietal network, during a WM task in 20 healthy participants. TDCS had no significant impact on behavioral measures, including reaction time and accuracy. Analyzing the electrophysiological response, the P300 amplitude significantly increased following repetitive anodal TDCS, however, positively correlating with task performance. P300 changes were identified over the parietal cortex, which is known to engage with the frontal cortex during WM processing. These findings support the hypothesis that repetitive anodal TDCS modulates electrophysiological processes underlying WM.

Transcranial direct current stimulation for balance rehabilitation in neurological disorders: A systematic review and meta-analysis

Postural instability is common in neurological diseases. Although transcranial direct current stimulation (tDCS) seems to be a promising complementary therapy, emerging evidence indicates mixed results and protocols' characteristics. We conducted a systematic review and meta-analysis on PubMed, EMBASE, Scopus, and Web of Science to synthesize key findings of the effectiveness of single and multiple sessions of tDCS alone and combined with other interventions on balance in adults with neurological disorders. Thirty-seven studies were included in the systematic review and 33 in the meta-analysis. The reviewed studies did not personalize the stimulation protocol to individual needs/characteristics. A random-effects meta-analysis indicated that tDCS alone (SMD = -0.44; 95%CI = -0.69/-0.19; p < 0.001) and combined with another intervention (SMD = -0.31; 95%CI = -0.51/-0.11; p = 0.002) improved balance in adults with neurological disorders (small to moderate effect sizes). Balance improvements were evidenced regardless of the number of sessions and targeted area. In summary, tDCS is a promising therapy for balance rehabilitation in adults with neurological disorders. However, further clinical trials should identify factors that influence responsiveness to tDCS for a more tailored approach, which may optimize the clinical use of tDCS.

The effects of aerobic exercise and transcranial direct current stimulation on cognitive function in older adults with and without cognitive impairment: A systematic review and meta-analysis

BACKGROUND

Aerobic exercise (AE) may slow age-related cognitive decline. However, such cognition-sparing effects are not uniform across cognitive domains and studies. Transcranial direct current stimulation (tDCS) is a form of non-invasive brain stimulation and is also emerging as a potential alternative to pharmaceutical therapies. Like AE, the effectiveness of tDCS is also inconsistent for reducing cognitive impairment in ageing. The unexplored possibility exists that pairing AE and tDCS could produce synergistic effects and reciprocally augment cognition-improving effects in older individuals with and without cognitive impairments. Previous research found such synergistic effects on cognition when cognitive training is paired with tDCS in older individuals with and without mild cognitive impairment (MCI) or dementia.

AIM

The purpose of this systematic review with meta-analysis was to explore if pairing AE with tDCS could augment singular effects of AE and tDCS on global cognition (GC), working memory (WM) and executive function (EF) in older individuals with or without MCI and dementia.

METHODS

Using a PRISMA-based systematic review, we compiled studies that examined the effects of AE alone, tDCS alone, and AE and tDCS combined on cognitive function in older individuals with and without mild cognitive impairment (MCI) or dementia. Using a PICOS approach, we systematically searched PubMed, Scopus and Web of Science searches up to December 2021, we focused on 'MoCA', 'MMSE', 'Mini-Cog' (measures) and 'cognition', 'cognitive function', 'cognitive', 'cognitive performance', 'executive function', 'executive process', 'attention', 'memory', 'memory performance' (outcome terms). We included only randomized controlled trials (RTC) in humans if available in English full text over the past 20 years, with participants' age over 60. We assessed the methodological quality of the included studies (RTC) by the Physiotherapy Evidence Database (PEDro) scale.

RESULTS

Overall, 68 studies were included in the meta-analyses. AE (ES = 0.56 [95% CI: 0.28-0.83], p = 0.01) and tDCS (ES = 0.69 [95% CI: 0.12-1.26], p = 0.02) improved GC in all three groups of older adults combined (healthy, MCI, demented). In healthy population, AE improved GC (ES = 0.46 [95% CI: 0.22-0.69], p = 0.01) and EF (ES = 0.27 [95% CI: 0.05-0.49], p = 0.02). AE improved GC in older adults with MCI (ES = 0.76 [95% CI: 0.21-1.32], p = 0.01). tDCS improved GC (ES = 0.69 [90% CI: 0.12-1.26], p = 0.02), all three cognitive function (GC, WM and EF) combined in older adults with dementia (ES = 1.12 [95% CI: 0.04-2.19], p = 0.04) and improved cognitive function in older adults overall (ES = 0.69 [95% CI: 0.20-1,18], p = 0.01).

CONCLUSION

Our systematic review with meta-analysis provided evidence that beyond the cardiovascular and fitness benefits of AE, pairing AE with tDCS may have the potential to slow symptom progression of cognitive decline in MCI and dementia. Future studies will examine the hypothesis of this present review that a potentiating effect would incrementally improve cognition with increasing severity of cognitive impairment.

Does the involvement of motor cortex in embodied language comprehension stand on solid ground? A p-curve analysis and test for excess significance of the TMS and tDCS evidence

According to the embodied cognition view, comprehending action-related language requires the participation of sensorimotor processes. A now sizeable literature has tested this proposal by stimulating (with TMS or tDCS) motor brain areas during the comprehension of action language. To assess the evidential value of this body of research, we exhaustively searched the literature and submitted the relevant studies (N = 43) to p-curve analysis. While most published studies concluded in support of the embodiment hypothesis, our results suggest that we cannot yet assert beyond reasonable doubt that they explore real effects. We also found that these studies are quite underpowered (estimated power < 30%), which means that a large percentage of them would not replicate if repeated identically. Additional tests for excess significance show signs of publication bias within this literature. In sum, extant brain stimulation studies testing the grounding of action language in the motor cortex do not stand on solid ground. We provide recommendations that will be important for future research on this topic.

Association of Transcranial Direct Current Stimulation and Neurofeedback With Declarative Memory and Cerebral Arterial Flow in University Students: Protocol for a Double-blind Randomized Controlled Study

BACKGROUND

The performance of a task depends on ongoing brain activity, which can be influenced by attention, excitement, or motivation. Scientific studies have confirmed that mindfulness leads to better performance, health, and well-being. However, these cognitive efficiency modulating factors are nonspecific, can be difficult to control, and are not suitable to specifically facilitate neural processing.

OBJECTIVE

The aim of this study is to evaluate the effects of transcranial direct current stimulation associated with neurofeedback on declarative memory and cerebral blood flow in university students.

METHODS

In this study, we will use transcranial direct current stimulation, a low-cost physical resource that is easy to apply, has few adverse effects, and is associated with a neurofeedback resource. This, in turn, has been shown to be a training program capable of improving working memory function.

RESULTS

Participants will be recruited between July 2022 and December 2022. This study is expected to conclude in July 2023.

CONCLUSIONS

This study will provide preliminary results on the benefits of using the direct current neurostimulation and neurofeedback tools on the participants being analyzed.

TRIAL REGISTRATION

Brazilian Clinical Trials Registry RBR-7zs8b5; https://ensaiosclinicos.gov.br/rg/RBR-7zs8b5.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/36294.

Adjunctive tDCS for treatment-refractory auditory hallucinations in schizophrenia: A meta-analysis of randomized, double-blinded, sham-controlled studies

OBJECTIVE

Treatment-refractory auditory hallucinations (TRAH) in schizophrenia often do not improve with pharmacotherapy. We performed a meta-analysis of randomized, double-blind, sham-controlled clinical trials (RCTs) that systematically examined the therapeutic effects and tolerability of adjunctive active versus sham active transcranial direct current stimulation (tDCS) for auditory hallucinations as measured by the Auditory Hallucination Rating Scale (AHRS) in schizophrenia patients with TRAH.

METHODS

Relevant data were extracted, checked and analyzed using the Review Manager, Version 5.3 by three independent investigators.

RESULTS

Eight double-blind RCTs covering 329 schizophrenia patients (168 in active tDCS group, 161 in sham tDCS group) were included. Although no advantage of active tDCS on auditory hallucinations [7 RCTs, n = 224; standardized mean difference (SMD): - 0.33 (95% confidence interval (CI): - 0.71, 0.05), P = 0.09; I² = 46%] was found compared to sham, subgroup analyses revealed that active tDCS with twice-daily stimulation [6 RCTs, n = 198; SMD: - 0.42 (95%CI: -0.82, -0.02), P = 0.04; I² = 44%] and active tDCS with ≥ 10 stimulation sessions [6 RCTs, n = 198; SMD: - 0.42 (95%CI: -0.82, -0.02), P = 0.04; I² = 44%] showed a significantly better therapeutic effect than sham in improving auditory hallucinations symptoms. Meta-analyses of total psychopathology and discontinuation due to any reason were not significantly different between the active and sham tDCS groups.

CONCLUSION

This meta-analysis demonstrated that the effects of tDCS for auditory hallucinations symptoms were influenced by the tDCS parameters. Twice-daily stimulation and ≥ 10 stimulation sessions may be needed to improve auditory hallucinations symptoms in schizophrenia with TRAH.

Brain stimulation and other biological non-pharmacological interventions in mental disorders: An umbrella review

BACKGROUND

The degree of efficacy, safety, quality, and certainty of meta-analytic evidence of biological non-pharmacological treatments in mental disorders is unclear.

METHODS

We conducted an umbrella review (PubMed/Cochrane Library/PsycINFO-04-Jul-2021, PROSPERO/CRD42020158827) for meta-analyses of randomized controlled trials (RCTs) on deep brain stimulation (DBS), transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), electro-convulsive therapy (ECT), and others. Co-primary outcomes were standardized mean differences (SMD) of disease-specific symptoms, and acceptability (for all-cause discontinuation). Evidence was assessed with AMSTAR/AMSTAR-Content/GRADE.

RESULTS

We selected 102 meta-analyses. Effective interventions compared to sham were in depressive disorders: ECT (SMD=0.91/GRADE=moderate), TMS (SMD=0.51/GRADE=moderate), tDCS (SMD=0.46/GRADE=low), DBS (SMD=0.42/GRADE=very low), light therapy (SMD=0.41/GRADE=low); schizophrenia: ECT (SMD=0.88/GRADE=moderate), tDCS (SMD=0.45/GRADE=very low), TMS (prefrontal theta-burst, SMD=0.58/GRADE=low; left-temporoparietal, SMD=0.42/GRADE=low); substance use disorder: TMS (high frequency-dorsolateral-prefrontal-deep (SMD=1.16/GRADE=moderate), high frequency-left dorsolateral-prefrontal (SMD=0.77/GRADE=very low); OCD: DBS (SMD=0.89/GRADE=moderate), TMS (SMD=0.64/GRADE=very low); PTSD: TMS (SMD=0.46/GRADE=moderate); generalized anxiety disorder: TMS (SMD=0.68/GRADE=low); ADHD: tDCS (SMD=0.23/GRADE=moderate); autism: tDCS (SMD=0.97/GRADE=very low). No significant differences for acceptability emerged. Median AMSTAR/AMSTAR-Content was 8/2 (suggesting high-quality meta-analyses/low-quality RCTs), GRADE low.

DISCUSSION

Despite limited certainty, biological non-pharmacological interventions are effective and safe for numerous mental conditions. Results inform future research, and guidelines.

FUNDING

None.

The effect of transcranial direct current stimulation (tDCS) combined with cognitive training on EEG spectral power in adolescent boys with ADHD: A double-blind, randomized, sham-controlled trial

Transcranial direct current stimulation (tDCS) is a possible alternative to psychostimulants in Attention-Deficit/Hyperactivity Disorder (ADHD), but its mechanisms of action in children and adolescents with ADHD are poorly understood. We conducted the first 15-session, sham-controlled study of anodal tDCS over right inferior frontal cortex (rIFC) combined with cognitive training (CT) in 50 children/adolescents with ADHD. We investigated the mechanisms of action on resting and Go/No-Go Task-based QEEG measures in a subgroup of 23 participants with ADHD (n, sham = 10; anodal tDCS = 13). We failed to find a significant sham versus anodal tDCS group differences in QEEG spectral power during rest and Go/No-Go Task performance, a correlation between QEEG and Go/No-Go Task performance, and changes in clinical and cognitive measures. These findings extend the non-significant clinical and cognitive effects in our sample of 50 children/adolescents with ADHD. Given that the subgroup of 23 participants would have been underpowered, the interpretation of our findings is limited and should be used as a foundation for future investigations. Larger, adequately powered randomized controlled trials should explore different protocols titrated to the individual and using comprehensive measures to assess cognitive, clinical, and neural effects of tDCS and its underlying mechanisms of action in ADHD.

Timing is everything: Event-related transcranial direct current stimulation improves motor adaptation

BACKGROUND

There is a current discord between the foundational theories underpinning motor learning and how we currently apply transcranial direct current stimulation (TDCS): the former is dependent on tight coupling of events while the latter is conducted with very low temporal resolution.

OBJECTIVE

Here we aimed to investigate the temporal specificity of stimulation by applying TDCS in short epochs, and coincidentally with movement, during a motor adaptation task.

METHODS

Participants simultaneously adapted a reaching movement to two opposing velocity-dependent force-fields (clockwise and counter-clockwise), distinguished by a contextual leftward or rightward shift in the task display and cursor location respectively. Brief bouts (<3 s) of event-related TDCS (er-TDCS) were applied over M1 or the cerebellum during movements for only one of these learning contexts.

RESULTS

We show that when short duration stimulation is applied to the cerebellum and yoked to movement, only those reaching movements performed simultaneously with stimulation are selectively enhanced, whilst similar and interleaved movements are left unaffected. We found no evidence of improved adaptation following M1 er-TDCS, as participants displayed equivalent levels of error during both stimulated and unstimulated movements. Similarly, participants in the sham stimulation group adapted comparably during left and right-shift trials.

CONCLUSIONS

It is proposed that the coupling of cerebellar stimulation and movement influences timing-dependent (i.e. Hebbian-like) mechanisms of plasticity to facilitate enhanced learning in the stimulated context.

A randomized, double-blind and sham-controlled tDCS study

Hypnotizability refers to the individual responsiveness to hypnosis, and literature shows that the greater the hypnotizability, the more effective the hypnotic suggestions. So far, few studies attempted to enhance hypnotizability, and only two adopted brain stimulation with magnetic pulses. In the present study, we aimed to boost hypnotizability through transcranial direct current stimulation (tDCS). To this aim, bilateral tDCS was applied over the dorsolateral prefrontal cortex (DLPFC) with the target electrode providing negative current (cathodal stimulation) over the left hemisphere. Twenty-nine subjects participated in the study and they were randomly assigned to the sham or the active group in a double-blind design. The hypnotic experience was assessed before and after the stimulation through a phenomenological measure of consciousness (the PCI-HAP). The main findings revealed that a single tDCS session enhanced the hypnotic depth by 11% and reduced the volitional control by 30%, while no differences emerged in the sham group. This is the first study adopting the electrical neurostimulation to produce an alteration of hypnotizability and sense of agency, and confirmed the key-role of the DLPFC and executive control in the hypnotic phenomena. If confirmed, these findings could have relevant implications as enhanced hypnotizability could be translated into better outcomes for many hypnotic interventions.

The residential stability mindset increases racial in-group bias in empathy

With the deepening of internationalization, the population's mobility has greatly increased, which can impact people's intergroup relationships. The current research examined the hypothesis that residential mobility plays a crucial role in racial in-group bias in empathy (RIBE) with three studies. By manipulating the residential mobility/stability mindset and measuring subjective pain intensity ratings (Study 1) and event-related potentials (ERPs, Study 2) of Chinese adults on painful and neutral expressions of Asian and Caucasian faces, we found that the RIBE in subjective ratings and N1 amplitudes increased and P3 amplitudes decreased in the stability group. Transcranial direct current stimulation (tDCS) manipulation in Study 3 further found that anodal stimulation of the left dorsolateral prefrontal cortex (DLPFC) increased the RIBE of participants with residential stability experience but had no effect on those with residential mobility experience. As residential mobility continues to increase worldwide, we may observe concomitant changes in racial intergroup relationships.

Transcranial Direct Current Stimulation Reduces the Negative Impact of Mental Fatigue on Swimming Performance

The issue of using transcranial direct current stimulation (tDCS) to improve sport performance has recently been a topic of interest for researchers. The purpose of this study was to examine the effect of tDCS over left dorsolateral prefrontal cortex (DLPFC) on mental fatigue and physical performance in professional swimmers. Fifteen professional swimmers were randomly assigned in a single-blinded, randomized, counterbalanced order to sham, anodal and cathodal stimulation conditions. Mental fatigue was induced by using a 60-min modified Stroop color-word task. Subjective ratings of mental fatigue were measured before and after the stroop task. The results showed that only anodal tDCS of the left DLPFC reduces adverse effects of mental fatigue in 50-meter swimming performance, whereas cathodal stimulation had no significant effect.

Transcranial direct current stimulation for balance and gait in repetitive mild traumatic brain injury in rats

BACKGROUND

Balance impairment and lack of postural orientation are serious problems in patients with repetitive mild traumatic brain injury (mTBI).

OBJECTIVE

To investigate whether anodal transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) can improve balance control and gait in repetitive mTBI rat models.

METHODS

In this prospective animal study, 65 repetitive mTBI rats were randomly assigned to two groups: the tDCS group and the control group. To create repetitive mTBI model rats, we induced mTBI in the rats for 3 consecutive days. The tDCS group received one session of anodal tDCS over the M1 area 24 h after the third induced mTBI, while the control group did not receive tDCS treatment. Motor-evoked potential (MEP), foot-fault test, and rotarod test were evaluated before mTBI, before tDCS and after tDCS. The Mann-Whitney U test and Wilcoxon signed rank test were used to assess the effects of variables between the two groups.

RESULTS

Anodal tDCS over the M1 area significantly improved the amplitude of MEP in the tDCS group (p = 0.041). In addition, rotarod duration was significantly increased in the tDCS group (p = 0.001). The foot-fault ratio was slightly lower in the tDCS group, however, this was not statistically significant.

CONCLUSION

Anodal tDCS at the M1 area could significantly improve the amplitude of MEP and balance function in a repetitive mTBI rat model. We expect that anodal tDCS would have the potential to improve balance in patients with repetitive mTBI.

Does anodal tDCS improve basketball performance? A randomized controlled trial

Shooting precision as well as dribbling and agility are crucial components of performance in basketball. We examined the effects of anodal tDCS over the dominant primary motor cortex in supporting these basketball specific abilities. Fifty-two sports students were enrolled in a double-blind, randomized, placebo-controlled, crossover trial with two interventions. Twenty minutes of anodal 1 mA tDCS/sham tDCS were applied over the primary motor cortex of the dominant hemisphere. Basketball shooting precision (basketball shooting accuracy test) and basketball specific dribbling and agility (Illinois ball-dribbling test) were tested prior and after each intervention. Basketball shooting precision and basketball specific dribbling and agility improved after real tDCS but not after sham tDCS. ANOVAs show significant intervention*time effects on both the shooting accuracy test (F_1,51= 5.6; P = 0.022) and on the Illinois ball-dribbling test (F_1,51 = 4.5; P = 0.038). Anodal 1 mA tDCS over the dominant primary motor cortex is effective in supporting short-term performance in basketball. However, the available data is insufficient for application of this novel method within the framework of conventional sports training.

Acute effects of transcranial direct current stimulation on cycling and running performance. A systematic review and meta-analysis

Transcranial direct current stimulation (tDCS) has been proven to induce positive effects on athletic performance. The present study aimed to analyse the effect of anodal-tDCS on endurance (time to exhaustion [TTE] or endurance time trial [ETT]) and sprint performance during cycling and running tasks. We performed a systematic literature review in the databases Medline (via PubMed), SPORTDiscus and Science Direct. We included only randomised controlled trials conducted with healthy individuals in which an anodal-tDCS protocol was applied prior to cycling or running tests. The effect of anodal-tDCS (experimental condition) was compared against sham stimulation (control condition). A total of 15 interventions from 13 studies were included. The sub-group analysis revealed a positive effect of anodal-tDCS on TTE (standardised mean differences [SMD] = 0.37; 90% confidence interval [CI] = 0.13, 0.61; p = 0.01), but not on ETT (SMD = 0.00; 90% CI = -0.29, 0.30; p = 1.00) or sprint performance (SMD = 0.19; 90% CI = -0.23, 0.60; p = 0.46). The current meta-analysis suggests that the effect of anodal-tDCS on whole-body dynamic exercises (running and cycling) could be task dependent. Specifically, anodal-tDCS enhance running and cycling time to exhaustion performance during TTE tasks but not ETT or sprint tasks. The increase in cortical excitability induced by anodal-tDCS may lead to lower ratings of perceived exertion by reducing the input required to perform the physical task. Task should be taken into account, because it is probably influencing the result obtained by anodal-tDCS.

Citizen Neuroscience: Brain-Computer Interface Researcher Perspectives on Do-It-Yourself Brain Research

Devices that record from and stimulate the brain are currently available for consumer use. The increasing sophistication and resolution of these devices provide consumers with the opportunity to engage in do-it-yourself brain research and contribute to neuroscience knowledge. The rise of do-it-yourself (DIY) neuroscience may provide an enriched fund of neural data for researchers, but also raises difficult questions about data quality, standards, and the boundaries of scientific practice. We administered an online survey to brain-computer interface (BCI) researchers to gather their perspectives on DIY brain research. While BCI researcher concerns about data quality and reproducibility were high, the possibility of expert validation of data generated by citizen neuroscientists mitigated concerns. We discuss survey results in the context of an established ethical framework for citizen science, and describe the potential of constructive collaboration between citizens and researchers to both increase data collection and advance understanding of how the brain operates outside the confines of the lab.

Behavioral and electrophysiological effects of network-based frontoparietal tDCS in patients with severe brain injury: A randomized controlled trial

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Behavioral and EEG effects of multifocal frontoparietal tDCS are investigated in patients with severe brain injury.

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No behavioral treatment effect was identified at the group level while EEG complexity increased in low frequency bands.

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Electrophysiological changes were not translated into behavioral changes at the group level.

Background

Transcranial direct current stimulation (tDCS) may promote the recovery of severely brain-injured patients with disorders of consciousness (DOC). Prior tDCS studies targeted single brain regions rather than brain networks critical for consciousness recovery.

Objective

Investigate the behavioral and electrophysiological effects of multifocal tDCS applied over the frontoparietal external awareness network in patients with chronic acquired DOC.

Methods

Forty-six patients were included in this randomized double-blind sham-controlled crossover trial (median [interquartile range]: 46 [35 – 59] years old; 12 [5 – 47] months post injury; 17 unresponsive wakefulness syndrome, 23 minimally conscious state (MCS) and 6 emerged from the MCS). Multifocal tDCS was applied for 20 min using 4 anodes and 4 cathodes with 1 mA per electrode. Coma Recovery Scale-Revised (CRS-R) assessment and 10 min of resting state electroencephalogram (EEG) recordings were acquired before and after the active and sham sessions.

Results

At the group level, there was no tDCS behavioral treatment effect. However, following active tDCS, the EEG complexity significantly increased in low frequency bands (1–8 Hz). CRS-R total score improvement was associated with decreased baseline complexity in those bands. At the individual level, after active tDCS, new behaviors consistent with conscious awareness emerged in 5 patients. Conversely, 3 patients lost behaviors consistent with conscious awareness.

Conclusion

The behavioral effect of multifocal frontoparietal tDCS varies across patients with DOC. Electrophysiological changes were observed in low frequency bands but not translated into behavioral changes at the group level.

Is It Possible to Improve Working Memory With Prefrontal tDCS? Bridging Currents to Working Memory Models

A great deal of research has been performed with the promise of improving such critical cognitive functions as working memory (WM), with transcranial direct current stimulation (tDCS), a well-tolerated, inexpensive, easy-to-use intervention. Under the assumption that by delivering currents through electrodes placed in suitable locations on the scalp, it is possible to increase prefrontal cortex excitability and therefore improve WM. A growing number of studies have led to mixed results, leading to the realization that such oversimplified assumptions need revision. Models spanning currents to behavior have been advocated in order to reconcile and inform neurostimulation investigations. We articulate such multilevel exploration to tDCS/WM by briefly reviewing critical aspects at each level of analysis but focusing on the circuit level and how available biophysical WM models could inform tDCS. Indeed, such models should replace vague reference to cortical excitability changes with relevant tDCS net effects affecting neural computation and behavior in a more predictable manner. We will refer to emerging WM models and explore to what extent the general concept of excitation-inhibition (E/I) balance is a meaningful intermediate level of analysis, its relationship with gamma oscillatory activity, and the extent to which it can index tDCS effects. We will highlight some predictions that appear consistent with empirical evidence – such as non-linearities and trait dependency of effects and possibly a preferential effect on WM control functions – as well as limitations that appear related to the dynamical aspects of coding by persistent activity.

A randomized controlled trial of transcranial direct-current stimulation and cognitive training in children with fetal alcohol spectrum disorder

BACKGROUND

This study was a randomized double-blind sham-controlled trial examining the effects of transcranial direct current stimulation (tDCS) augmented cognitive training (CT) in children with Fetal Alcohol Spectrum Disorders (FASD). Prenatal alcohol exposure has profound detrimental effects on brain development and individuals with FASD commonly present with deficits in executive functions including attention and working memory. The most commonly studied treatment for executive deficits is CT, which involves repeated drilling of exercises targeting the impaired functions. As currently implemented, CT requires many hours and the observed effect sizes are moderate. Neuromodulation via tDCS can enhance brain plasticity and prior studies demonstrate that combining tDCS with CT improves efficacy and functional outcomes. TDCS-augmented CT has not yet been tested in FASD, a condition in which there are known abnormalities in neuroplasticity and few interventions.

METHODS

This study examined the feasibility and efficacy of this approach in 44 children with FASD. Participants were randomized to receive five sessions of CT with either active or sham tDCS targeting the dorsolateral prefrontal cortex, a region of the brain that is heavily involved in executive functioning.

RESULTS

The intervention was feasible and well-tolerated in children with FASD. The tDCS group showed nominally significant improvement in attention on a continuous performance test compared to sham (p = .043). Group differences were observed at the third, fourth and fifth treatment sessions. There was no effect of tDCS on working memory (p = .911). Further, we found no group differences on a trail making task (p = .659) or on the verbal fluency test (p = .826). In the active tDCS group, a significant correlation was observed between improvement in attention scores and decrease in parent-reported attention deficits (p = .010).

CONCLUSIONS

These results demonstrate that tDCS-augmented CT is well tolerated in children with FASD and potentially offers benefits over and above CT alone.

Testing the effects of transcranial direct current stimulation (tDCS) on the face inversion effect and the N170 event-related potentials (ERPs) component

The following study investigates the effects of tDCS on face recognition skills indexed by the face inversion effect (better recognition performance for upright vs. inverted faces). We combined tDCS and EEG simultaneously to examine the effects of tDCS on the face inversion effect behaviourally and on the N170 ERPs component. The results from two experiments (overall N = 112) show that anodal tDCS delivered at Fp3 site for 10 min at 1.5 mA (double-blind and between-subjects) can reduce behaviourally the face inversion effect compared to sham (control) stimulation. The ERP results provide some evidence for tDCS being able to influence the face inversion effect on the N170. Specifically, we find a dissociation of the tDCS-induced effects where for the N170 latencies the tDCS reduces the usual face inversion effect (delayed N170 in response to inverted vs. upright faces) compared to sham. Contrarily, the same tDCS procedure on the same participants increased the inversion effect seen in the N170 amplitudes by making the negative deflection for the inverted faces that much greater than that for upright faces. We interpret our results in the context of the literature on the face inversion effect and the N170 peak component. In doing so, we extend our results to previous studies investigating the effects of tDCS on perceptual learning and face recognition.

No evidence for any effect of multiple sessions of frontal transcranial direct stimulation on mood in healthy older adults

The dorsolateral prefrontal cortex (DLPFC) is part of a network important for emotional regulation and the possibility of modulating activity in this region with transcranial direct current stimulation (TDCS) to change mood has gained great interest, particularly for application in clinical populations. Whilst results in major depressive disorder have been promising, less is known about the effects of TDCS on mood in non-clinical populations. We hypothesized that multiple sessions of anodal TDCS applied over the left DLPFC would enhance mood, primarily as measured by the Profile of Mood States questionnaire, in healthy older adults. In addition, in an exploratory analysis, we examined the potentially moderating role of working memory training. Working memory, just like emotional regulation, taxes the DLPFC, which suggests that engaging in a working memory task whilst receiving TDCS may have a different effect on activity in this region and consequently mood. A total of 123 participants between 65 and 75 years of age were randomly assigned to receive either 20 sessions of TDCS, with or without working memory training, or 20 sessions sham stimulation, with or without working memory training. We found no support for enhancement of mood due to TDCS in healthy older adults, with or without cognitive training and conclude that the TDCS protocol used is unlikely to improve mood in non-depressed older individuals.

Combining reward and M1 transcranial direct current stimulation enhances the retention of newly learnt sensorimotor mappings

Background

Reward-based feedback given during motor learning has been shown to improve the retention of the behaviour being acquired. Interestingly, applying transcranial direct current stimulation (tDCS) during learning over the primary motor cortex (M1), an area associated with motor retention, also results in enhanced retention of the newly formed motor memories. However, it remains unknown whether combining these distinct interventions result in an additive benefit of motor retention.

Methods

We investigated whether combining both interventions while participants learned to account for a visuomotor transformation results in enhanced motor retention (total n = 56; each group n = 14). To determine whether these interventions share common physiological mechanisms underpinning learning, we assessed motor cortical excitability and inhibition (i.e. SICI) on a hand muscle before and after all participants learned the visuomotor rotation using their entire arm and hand.

Results

We found that both the Reward-Stim (i.e. reward + tDCS) and Reward-Sham (i.e. reward-only) groups had increased retention at the beginning of the retention phase, indicating an immediate effect of reward on behaviour. However, each intervention on their own did not enhance retention when compared to sham, but rather, only the combination of both reward and tDCS demonstrated prolonged retention. We also found that only the Reward-Stim group had a significant reduction in SICI after exposure to the perturbation.

Conclusions

We show that combining both interventions are additive in providing stronger retention of motor adaptation. These results indicate that the reliability and validity of using tDCS within a clinical context may depend on the type of feedback individuals receive when learning a new motor pattern.

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Concurrently administering reward and M1 tDCS during learning results in enhanced motor retention.

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The combination of these interventions also leads to a reduction in M1 inhibitory mechanisms.

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No benefits of motor retention were found when reward or M1 tDCS were given alone.

Cognitive enhancement with Salience Network electrical stimulation is influenced by network structural connectivity

The Salience Network (SN) and its interactions are important for cognitive control. We have previously shown that structural damage to the SN is associated with abnormal functional connectivity between the SN and Default Mode Network (DMN), abnormal DMN deactivation, and impaired response inhibition, which is an important aspect of cognitive control. This suggests that stimulating the SN might enhance cognitive control. Here, we tested whether non-invasive transcranial direct current stimulation (TDCS) could be used to modulate activity within the SN and enhance cognitive control. TDCS was applied to the right inferior frontal gyrus/anterior insula cortex during performance of the Stop Signal Task (SST) and concurrent functional (f)MRI. Anodal TDCS improved response inhibition. Furthermore, stratification of participants based on SN structural connectivity showed that it was an important influence on both behavioural and physiological responses to anodal TDCS. Participants with high fractional anisotropy within the SN showed improved SST performance and increased activation of the SN with anodal TDCS, whilst those with low fractional anisotropy within the SN did not. Cathodal stimulation of the SN produced activation of the right caudate, an effect which was not modulated by SN structural connectivity. Our results show that stimulation targeted to the SN can improve response inhibition, supporting the causal influence of this network on cognitive control and confirming it as a target to produce cognitive enhancement. Our results also highlight the importance of structural connectivity as a modulator of network to TDCS, which should guide the design and interpretation of future stimulation studies.

Locating primary somatosensory cortex in human brain stimulation studies: experimental evidence

Transcranial magnetic stimulation (TMS) over human primary somatosensory cortex (S1) does not produce immediate outputs. Researchers must therefore rely on indirect methods for TMS coil positioning. The "gold standard" is to use individual functional and structural magnetic resonance imaging (MRI) data, but the majority of studies don't do this. The most common method to locate the hand area of S1 (S1-hand) is to move the coil posteriorly from the hand area of primary motor cortex (M1-hand). Yet, S1-hand is not directly posterior to M1-hand. We localized the index finger area of S1-hand (S1-index) experimentally in four ways. First, we reanalyzed functional MRI data from 20 participants who received vibrotactile stimulation to their 10 digits. Second, to assist the localization of S1-hand without MRI data, we constructed a probabilistic atlas of the central sulcus from 100 healthy adult MRIs and measured the likely scalp location of S1-index. Third, we conducted two experiments mapping the effects of TMS across the scalp on tactile discrimination performance. Fourth, we examined all available neuronavigation data from our laboratory on the scalp location of S1-index. Contrary to the prevailing method, and consistent with systematic review evidence, S1-index is close to the C3/C4 electroencephalography (EEG) electrode locations on the scalp, ~7-8 cm lateral to the vertex, and ~2 cm lateral and 0.5 cm posterior to the M1-hand scalp location. These results suggest that an immediate revision to the most commonly used heuristic to locate S1-hand is required. The results of many TMS studies of S1-hand need reassessment. NEW & NOTEWORTHY Noninvasive human brain stimulation requires indirect methods to target particular brain areas. Magnetic stimulation studies of human primary somatosensory cortex have used scalp-based heuristics to find the target, typically locating it 2 cm posterior to the motor cortex. We measured the scalp location of the hand area of primary somatosensory cortex and found that it is ~2 cm lateral to motor cortex. Our results suggest an immediate revision of the prevailing method is required.

Hospital production cost of transcranial direct current stimulation (tDCS) in the treatment of depression

OBJECTIVES

Due to its ease of use, tolerance, and cost of acquisition, transcranial direct current stimulation (tDCS) could constitute a credible therapeutic option for non-resistant depression in primary care, when combined with drug management. This indication has yet to receive official recognition in France. The objective of this study is to evaluate the production cost of tDCS for the treatment of depression in hospitals, under realistic conditions.

METHODS

The methodology adopted is based on cost accounting and was validated by a multidisciplinary working group. It includes equipment, staff, and structural costs to obtain the most realistic estimate possible. We first estimated the cost of producing a tDCS session, based on our annual activity objective, and then estimated the cost of a 15-session treatment program. This was followed up with a sensitivity analysis applying appropriate parameters.

RESULTS

The hospital production cost of a tDCS depression treatment program for a single patient was estimated at €1555.60 euros: €99 in equipment costs, €1076.95 in staff costs, and €379.65 in structural costs.

CONCLUSION

This cost analysis should make it possible to draw up pricing proposals in compliance with regulations and health policy choices and to develop health-economic studies. This would ultimately lead to official recognition of tDCS treatment for depression in France and pave the way for studying various scenarios of coverage by the French national health insurance system.

Modulation of Working Memory Using Transcranial Electrical Stimulation: A Direct Comparison Between TACS and TDCS

Transcranial electrical stimulation (TES) has been considered a promising tool for improving working memory (WM) performance. Recent studies have demonstrated modulation of networks underpinning WM processing through application of transcranial alternating current (TACS) as well as direct current (TDCS) stimulation. Differences between study designs have limited direct comparison of the efficacy of these approaches, however. Here we directly compared the effects of theta TACS (6 Hz) and anodal TDCS on WM, applying TACS to the frontal-parietal loop and TDCS to the dorsolateral prefrontal cortex (DLPFC). WM was evaluated using a visual 2-back WM task. A within-subject, crossover design was applied (N = 30) in three separate sessions. TACS, TDCS, and sham stimulation were administered in a counterbalanced order, and the WM task was performed before, during, and after stimulation. Neither reaction times for hits (RT-hit) nor accuracy differed according to stimulation type with this study design. A marked practice effect was noted, however, with improvement in RT-hit irrespective of stimulation type, which peaked at the end of the second session. Pre-stimulation RT-hits in session three returned to the level observed pre-stimulation in session two, irrespective of stimulation type. The participants who received sham stimulation in session one and had therefore improved their performance due to practice alone, had thus reached a plateau by session two, enabling us to pool RT-hits from sessions two and three for these participants. The pooling allowed implementation of a within-subject crossover study design, with a direct comparison of the effects of TACS and TDCS in a subgroup of participants (N = 10), each of whom received both stimulation types, in a counterbalanced order, with pre-stimulation performance the same for both sessions. TACS resulted in a greater improvement in RT-hits than TDCS (F(2,18) = 4.31 p = 0.03). Our findings suggest that future work optimizing the application of TACS has the potential to facilitate WM performance.

Effects of prefrontal tDCS on executive function: Methodological considerations revealed by meta-analysis

A meta-analysis of studies using single-session transcranial direct current stimulation (tDCS) to target the dorsolateral prefrontal cortex (DLPFC) was undertaken to examine the effect of stimulation on executive function (EF) in healthy samples. 27 studies were included in analyses, yielding 71 effect sizes. The most relevant measure for each task was determined a priori and used to calculate Hedge's g. Methodological characteristics of each study were examined individually as potential moderators of effect size. Stimulation effects on three domains of EF (inhibition of prepotent responses, mental set shifting, and information updating and monitoring) were analyzed separately. In line with previous work, the current study found no significant effect of anodal unilateral tDCS, cathodal unilateral tDCS, or bilateral tDCS on EF. Further moderator and subgroup analyses were only carried out for anodal unilateral montages due to the small number of studies using other montages. Subgroup analyses revealed a significant effect of anodal unilateral tDCS on updating tasks, but not on inhibition or set-shifting tasks. Cathode location significantly moderated the effect of anodal unilateral tDCS. Extracranial cathodes yielded a significant effect on EF while cranial cathodes yielded no effect. Anode size also significantly moderated effect of anodal unilateral tDCS, with smaller anodes being more effective than larger anodes. In summary, anodal DLPFC stimulation is more effective at improving updating ability than inhibition and set-shifting ability, but anodal stimulation can significantly improve general executive function when extracranial cathodes or small anodes are used. Future meta-analyses may examine how stimulation's effects on specific behavioral tasks, rather than broader domains, might be affected by methodological moderators.

Metaplasticity: A Promising Tool to Disentangle Chronic Disorders of Consciousness Differential Diagnosis

The extent of cortical reorganization after brain injury in patients with Vegetative State/Unresponsive Wakefulness Syndrome (UWS) and Minimally Conscious State (MCS) depends on the residual capability of modulating synaptic plasticity. Neuroplasticity is largely abnormal in patients with UWS, although the fragments of cortical activity may exist, while patients MCS show a better cortical organization. The aim of this study was to evaluate cortical excitability in patients with disorders of consciousness (DoC) using a transcranial direct current stimulation (TDCS) metaplasticity protocol. To this end, we tested motor-evoked potential (MEP) amplitude, short intracortical inhibition (SICI), and intracortical facilitation (ICF). These measures were correlated with the level of consciousness (by the Coma Recovery Scale-Revised, CRS-R). MEP amplitude, SICI, and ICF strength were significantly modulated following different metaplasticity TDCS protocols only in the patients with MCS. SICI modulations showed a significant correlation with the CRS-R score. Our findings demonstrate, for the first time, a partial preservation of metaplasticity properties in some patients with DoC, which correlates with the level of awareness. Thus, metaplasticity assessment may help the clinician in differentiating the patients with DoC, besides the clinical evaluation. Moreover, the responsiveness to metaplasticity protocols may identify the subjects who could benefit from neuromodulation protocols.

Effect of transcranial direct current stimulation combined with cognitive training on cognitive functioning in older adults with HIV: A pilot study

The objective of this study was to examine combination speed of processing (SOP) cognitive remediation therapy (CRT) and transcranial direct stimulation (tDCS) as neurorehabilitation in older HIV+ adults. Thirty-three HIV+ adults aged 50+ completed neurocognitive testing and were randomized to either active (n = 17) or sham (n = 16) tDCS. Both conditions received 10 1-hour sessions of SOP CRT, with either active or sham tDCS for the first 20 minutes. Participants then completed a posttest assessment. Repeated measures analysis of variance examining Time X Condition showed small-to-medium effects in the expected direction for an executive (d = 0.36), and SOP measure (d = 0.49), while medium-to-large effects were observed for an executive/attention (d = 0.60) and oral reading measure (d = 0.75). The only statistically significant interaction was the oral reading measure. Small-to-medium and medium-to-large effects (ds = 0.32, 0.58) were found for two SOP measures in the opposite direction (sham group showing greater improvements). Further trials of CRT and tDCS in this population are needed, including larger samples and a nonactive control and tDCS only condition, as is determination of which parameters of each technique (e.g., tDCS montage, timing of tDCS, domain targeted in CRT, number of sessions) are most effective in improving cognitive outcomes, durability of training gains, and translation to everyday functioning.

Evaluation of Numerical Techniques for Solving the Current Injection Problem in Biological Tissues

Accurate computational modeling of electric fields in the human head has become important in clinical research to study or influence brain functionality. While existing numerical approaches have been evaluated against simple geometries with known closed form solutions, the relationship between these approaches in more complex geometries has not been studied. Here, we compare the three most commonly used approaches for bioelectric modeling: the finite element method (FEM), the finite difference method (FDM), and the boundary element method (BEM). Using both isotropic and anisotropic conductivity distributions, we construct and compare bioelectric models for a realistic head geometry. Our results suggest that both FEM and FDM are capable of accurately model voltages in the brain, while computations from BEM result in significantly larger errors, due to the increased simplicity and implicit model assumptions.

Older Adults Improve on Everyday Tasks after Working Memory Training and Neurostimulation

BACKGROUND

Aging is associated with decline in executive function (EF), upper-level cognitive abilities such as planning, problem solving, and working memory (WM). This decline is associated with age-related volume loss and reduced functional connectivity in the frontal lobes. Cognitive training interventions aim to counter these losses, but often fail to elicit benefits beyond improvements on trained tasks. Recent interventions pairing WM training with transcranial direct current stimulation (tDCS) have improved WM and elicited transfer to untrained EF tasks. Limitations in previous work include exclusive use of laboratory-based computer training and testing and poor characterization of the mechanism(s) of durable tDCS-linked change.

OBJECTIVE/HYPOTHESIS

To determine if tDCS-linked WM training improves performance on ecologically valid transfer measures administered in participants' homes. To explore intervention-based changes using neuroimaging (fNIRS) and genotyping (COMT val158met).

METHODS

90 healthy older adult participants completed 5 sessions of WM training paired with tDCS (Sham, 1 mA tDCS, 2 mA tDCS; 15 min). At follow-up, we assessed performance change on laboratory-based and ecologically valid tasks.

RESULTS

All participants showed improvement on trained tasks. Importantly, 2 mA of tDCS induced significantly greater far transfer gains after 1 month without contact. Gains were observed on standard far transfer tasks along with ecologically valid far transfer tasks, and stimulation was well tolerated by all participants. FNIRS and genotyping results were less conclusive, but provide promising avenues for future research initiatives.

CONCLUSION

These findings highlight the translational value for tDCS-based interventions in healthy older adults interested in maintaining cognitive function.

Constitutive expression of genes encoding notch receptors and ligands in developing lymphocytes, nTreg cells and dendritic cells in the human thymus

The thymus is the site of T cell maturation. Notch receptors (Notch1-4) and ligands (DLL1-3 and Jagged1-2) constitute one of several pathways involved in this process. Our data revealed differential constitutive expression of Notch genes and ligands in T lymphocytes and thymic dendritic cells (tDCs), suggesting their participation in human thymocyte maturation. nTreg analyses indicated that the Notch components function in parallel to promote maturation in the thymus.

Effects of adjustment of transcranial direct current stimulation on motor function of the upper extremity in stroke patients

[Purpose] The purpose of this study was to examine the effects of transcranial direct current stimulation (tDCS) applied to the cerebral cortex motor area on the upper extremity functions of hemiplegic patients. [Subjects and Methods] Twenty four Patients with hemiplegia resulting from a stroke were divided into two groups: a tDCS group that received tDCS and physical therapy and a control group that received only physical therapy. A functional evaluation of the two groups was performed, and an electrophysiological evaluation was conducted before and after the experiment. Statistical analyses were performed to verify differences before and after the experiment. All statistical significance levels were set at 0.05. [Results] The results showed that functional evaluation scores for the elbow joint and hand increased after the treatment in both the experimental group and the control group, and the increases were statistically significantly different. [Conclusion] tDCS was effective in improving the upper extremity motor function of stroke patients. Additional research is warranted on the usefulness of tDCS in the rehabilitation of stroke patients in the clinical field.

Effect of combination of transcranial direct current stimulation and feedback training on visuospatial neglect in patients with subacute stroke: a pilot randomized controlled trial

[Purpose] To investigate the effects of a combination of transcranial direct current stimulation (tDCS) and feedback training (FT) on subacute stroke patients with unilateral visuospatial neglect. [Subjects] The subjects were randomly assigned to a tDCS + FT group (n=6) and a FT group (n=6). [Methods] Patients in the tDCS + FT group received tDCS for 20 minutes and then received FT for 30 minutes a day, 5 days a week for 3 weeks. The control group received FT for 30 minutes a day, 5 days a week for 3 weeks. [Results] After the intervention, both groups showed significant improvements in the Motor-Free Visual Perception Test (MVPT), line bisection test (LBT), and modified Barthel index (MBI) over the baseline results. The comparison of the two groups after the intervention revealed that the rDCS + FT group showed more significant improvements in MVPT, LBT, and MBI. [Conclusion] The results of this study suggest that tDCS combined with FT has a positive effect on unilateral visuospatial neglect in patients with subacute stroke.

The role of the posterior cerebellum in saccadic adaptation: a transcranial direct current stimulation study

The posterior vermis of the cerebellum is considered to be critically involved in saccadic adaptation. However, recent evidence suggests that the adaptive decrease (backward adaptation) and the adaptive increase (forward adaptation) of saccade amplitude rely on partially separate neural substrates. We investigated whether the posterior cerebellum could be differentially involved in backward and forward adaptation by using transcranial direct current stimulation (TDCS). To do so, participants' saccades were adapted backward or forward while they received anodal, cathodal, or sham TDCS. In two extra groups, subjects underwent a nonadaptation session while receiving anodal or cathodal TDCS to control for the direct effects of TDCS on saccadic execution. Surprisingly, cathodal stimulation tended to increase the extent of both forward and backward adaptations, while anodal TDCS strongly impaired forward adaptation and, to a smaller extent, backward adaptation. Forward adaptation was accompanied by a greater increase in velocity with cathodal stimulation, and reduced duration of change for anodal stimulation. In contrast, the expected velocity decrease in backward adaptation was noticeably weaker with anodal stimulation. Stimulation applied during nonadaptation sessions did not affect saccadic gain, velocity, or duration, demonstrating that the reported effects are not due to direct effects of the stimulation on the generation of eye movements. Our results demonstrate that cerebellar excitability is critical for saccadic adaptation. Based on our results and the growing evidence from studies of vestibulo-ocular reflex and saccadic adaptation, we conclude that the plasticity at the level of the oculomotor vermis is more fundamentally important for forward adaptation than for backward adaptation.

Timing-dependent priming effects of tDCS on ankle motor skill learning

Transcranial direct current stimulation (tDCS) has gained increasing interest in neurorehabilitation with its ability to modulate cortical excitability, and thereby influence neural plasticity and functional recovery. While the beneficial effects of tDCS on motor learning and function have been recognized, there is no clear consensus regarding the timing of the tDCS priming protocol in relation to the intervention especially with respect to lower limb motor learning. Depending on the time of priming in relation to the training task, the neural mechanisms of priming (gating vs. homeostatic plasticity) are different and thereby subsequently affect motor learning. Hence, the aim of this study was to examine the interaction of tDCS with subsequent vs. concurrent motor learning using an ankle visuomotor skill learning paradigm. Twelve healthy participants were tested under three stimulation conditions: (1) anodal tDCS prior to the motor task (tDCS-before), (2) anodal tDCS during the motor task (tDCS-during) and (3) sham tDCS during the motor task (tDCS-sham). Results revealed that tDCS application during practice of a skilled motor task increased motor performance compared to tDCS applied prior to motor practice. Both tDCS groups demonstrated enhanced motor learning when tested 24 hours after practice. We conclude that the priming effects of tDCS are timing dependent, and maybe a critical regulatory feature in determining outcomes of priming with tDCS.

EEG mean frequency changes in healthy subjects during prefrontal transcranial direct current stimulation

In this pilot study we evaluated electroencephalographic (EEG) mean frequency changes induced by prefrontal transcranial direct current stimulation (tDCS) and investigated whether they depended on tDCS electrode montage. Eight healthy volunteers underwent tDCS for 15 min during EEG recording. They completed six tDCS sessions, 1 wk apart, testing left and right direct current (DC) dipole directions with six different montages: four unipolar montages (one electrode on a prefrontal area, the other on the opposite wrist) and two bipolar montages (both electrodes on prefrontal areas), and a single sham session. EEG power spectra were assessed from four 1-min EEG epochs, before, during, and after tDCS. During tDCS the outcome variable, brain rate (fb), changed significantly, and the changes persisted for minutes after tDCS ended. With the DC dipole directed to the left (anode on the left prefrontal area or wrist), fb increased, and with the DC dipole directed to the right (anode on the right prefrontal area or wrist), fb decreased, suggesting asymmetric prefrontal cortex functional organization in the normal human brain. Anodal and cathodal effects were opposite but equally large. Gender left these effects unchanged.

Effects of anodal TDCS stimulation of left parietal cortex on visual spatial attention tasks in men and women across menstrual cycle

Sex hormonal variations have been shown to affect functional cerebral asymmetries in cognitive domains, contributing to sex-related differences in functional cerebral organization. The aim of this study was to investigate spatial attention by means of a bisection line test and computer-supported attention task during the menstrual cycle in healthy women compared to men, in basal condition and under Transcranial Direct Current Stimulation (TDCS) of the left parietal cortex. Women were studied during the menses, follicular and luteal phases, ascertained by transvaginal ultrasounds. In basal conditions, women showed a clear deviation toward the right in the bisection line test during the menstrual phase, similarly to men. The midpoint recognition in the computer-supported attention task was not influenced by the menstrual cycle for women, while men showed a significant increase in errors toward the left side. The anodal activation of the left parietal cortex did not affect the line bisection task, while in men it reduced the total amount of errors in midpoint recognition observed in the computer supported attention task. The hand-use effect demonstrated by the bisection-line test could be influenced by estrogen fluctuations, while the right hemisphere prevalence in spatial attention appears to be gender-related and scarcely influenced by the menstrual cycle. The left parietal cortex seems to exert a scarce effect on hand-use effect, while its activation is able to revert sex related right hemisphere supremacy.

Cathodal transcranial direct current stimulation in children with dystonia: a pilot open-label trial

Studies suggest that dystonia is associated with increased motor cortex excitability. Cathodal transcranial direct current stimulation can temporarily reduce motor cortex excitability. To test whether stimulation of the motor cortex can reduce dystonic symptoms in children, we measured tracking performance and muscle overflow using an electromyogram tracking task before and after stimulation. Of 10 participants, 3 showed a significant reduction in overflow, and a fourth showed a significant reduction in tracking error. Overflow decreased more when the hand contralateral to the cathode performed the task than when the hand ipsilateral to the cathode performed the task. Averaged over all participants, the results did not reach statistical significance. These results suggest that cathodal stimulation may allow a subset of children to control muscles or reduce involuntary overflow activity. Further testing is needed to confirm these results in a blinded trial and identify the subset of children who are likely to respond.

Predicting behavioural response to TDCS in chronic motor stroke

Transcranial direct current stimulation (TDCS) of primary motor cortex (M1) can transiently improve paretic hand function in chronic stroke. However, responses are variable so there is incentive to try to improve efficacy and or to predict response in individual patients. Both excitatory (Anodal) stimulation of ipsilesional M1 and inhibitory (Cathodal) stimulation of contralesional M1 can speed simple reaction time. Here we tested whether combining these two effects simultaneously, by using a bilateral M1–M1 electrode montage, would improve efficacy. We tested the physiological efficacy of Bilateral, Anodal or Cathodal TDCS in changing motor evoked potentials (MEPs) in the healthy brain and their behavioural efficacy in changing reaction times with the paretic hand in chronic stroke. In addition, we aimed to identify clinical or neurochemical predictors of patients' behavioural response to TDCS. There were three main findings: 1) unlike Anodal and Cathodal TDCS, Bilateral M1–M1 TDCS (1 mA, 20 min) had no significant effect on MEPs in the healthy brain or on reaction time with the paretic hand in chronic stroke patients; 2) GABA levels in ipsilesional M1 predicted patients' behavioural gains from Anodal TDCS; and 3) although patients were in the chronic phase, time since stroke (and its combination with Fugl–Meyer score) was a positive predictor of behavioural gain from Cathodal TDCS. These findings indicate the superiority of Anodal or Cathodal over Bilateral TDCS in changing motor cortico-spinal excitability in the healthy brain and in speeding reaction time in chronic stroke. The identified clinical and neurochemical markers of behavioural response should help to inform the optimization of TDCS delivery and to predict patient outcome variability in future TDCS intervention studies in chronic motor stroke.

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Ipsilesional M1 GABA levels predict motor gains from Anodal TDCS in chronic stroke.

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Time since stroke and Fugl–Meyer score jointly predict response to Cathodal TDCS.

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Bilateral motor cortex TDCS did not reliably change motor evoked potentials.

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Bilateral motor cortex TDCS did not reliably change manual reaction time.