Neural Regulation Technology Combined with Functional Neuroimaging in Stroke Rehabilitation: Mechanism Research and Application Progress

International Conference on Transcranial Magnetic and Direct Current Stimulation

The purpose of this Third Stroke Recovery and Rehabilitation Roundtable (SRRR3) was to develop consensus recommendations to address outstanding barriers for the translation of preclinical and clinical research using the non-invasive brain stimulation (NIBS) techniques Transcranial Magnetic Stimulation (TMS) and Transcranial Direct Current Stimulation (tDCS) and provide a roadmap for the integration of these techniques into clinical practice. International NIBS and stroke recovery experts (N = 18) contributed to the consensus process. Using a nominal group technique, recommendations were reached via a five-stage process, involving a thematic survey, two priority ranking surveys, a literature review and an in-person meeting. Results of our consensus process yielded five key evidence-based and feasibility barriers for the translation of preclinical and clinical NIBS research, which were formulated into five core consensus recommendations. Recommendations highlight an urgent need for (1) increased understanding of NIBS mechanisms, (2) improved methodological rigor in both preclinical and clinical NIBS studies, (3) standardization of outcome measures, (4) increased clinical relevance in preclinical animal models, and (5) greater optimization and individualization of NIBS protocols. To facilitate the implementation of these recommendations, the expert panel developed a new SRRR3 Unified NIBS Research Checklist. These recommendations represent a translational pathway for the use of NIBS in stroke rehabilitation research and practice.

Background and Aims: The purpose of this Third Stroke Recovery and Rehabilitation Roundtable (SRRR3) was to develop consensus recommendations to address outstanding barriers for the translation of preclinical and clinical research using the non-invasive brain stimulation (NIBS) techniques Transcranial Magnetic Stimulation (TMS) and Transcranial Direct Current Stimulation (tDCS) and provide a roadmap for the integration of these techniques into clinical practice. Methods: International NIBS and stroke recovery experts (N = 18) contributed to the consensus process. Using a nominal group technique, recommendations were reached via a five-stage process, involving a thematic survey, two priority ranking surveys, a literature review and an in-person meeting. Results and Conclusions: Results of our consensus process yielded five key evidence-based and feasibility barriers for the translation of preclinical and clinical NIBS research, which were formulated into five core consensus recommendations. Recommendations highlight an urgent need for (1) increased understanding of NIBS mechanisms, (2) improved methodological rigor in both preclinical and clinical NIBS studies, (3) standardization of outcome measures, (4) increased clinical relevance in preclinical animal models, and (5) greater optimization and individualization of NIBS protocols. To facilitate the implementation of these recommendations, the expert panel developed a new SRRR3 Unified NIBS Research Checklist. These recommendations represent a translational pathway for the use of NIBS in stroke rehabilitation research and practice.

Background: Central post stroke pain (CPSP) is a highly refractory syndrome that can occur after stroke. Primary motor cortex (M1) brain stimulation using epidural brain stimulation (EBS), transcranial magnetic stimulation (TMS), and transcranial direct current stimulation (tDCS) have been explored as potential therapies for CPSP. These techniques have demonstrated variable clinical efficacy. It is hypothesized that changes in the stimulating currents that are caused by stroke-induced changes in brain tissue conductivity limit the efficacy of these techniques.Methods: We generated MRI-guided finite element models of the current density distributions in the human head and brain with and without chronic focal cortical infarctions during EBS, TMS, and tDCS. We studied the change in the stimulating current density distributions’ magnitude, orientation, and maxima locations between the different models.Results: Changes in electrical properties at stroke boundaries altered the distribution of stimulation currents in magnitude, location, and orientation. Current density magnitude alterations were larger for the non-invasive techniques (i.e., tDCS and TMS) than for EBS. Nonetheless, the lesion also altered currents during EBS. The spatial shift of peak current density, relative to the size of the stimulation source, was largest for EBS.Conclusion: In order to maximize therapeutic efficiency, neurostimulation trials need to account for the impact of anatomically disrupted neural tissues on the location, orientation, and magnitude of exogenously applied currents. The relative current-neuronal structure should be considered when planning stimulation treatment, especially across techniques (e.g., using TMS to predict EBS response). We postulate that the effects of altered tissue properties in stroke regions may impact stimulation induced analgesic effects and/or lead to highly variable outcomes during brain stimulation treatments in CPSP.

Transcranial magnetic stimulation

Transcranial magnetic and electrical stimulation compared: Does TES activate intracortical neuronal circuits?

A Physiological Marriage Made in Heaven: Treating and Measuring the Brain Through Stimulation.

Paralysis after stroke or neurotrauma is among the leading causes of long term disability in adults. The development of brain–computer interface (BCI) systems that allow online classification of electric or metabolic brain activity and their translation into control signals of external devices or computers have led to two major approaches in tackling the problem of paralysis. While assistive BCI systems strive for continuous high-dimensional control of robotic devices or functional electric stimulation (FES) of paralyzed muscles to substitute for lost motor functions in a daily life environment (e.g. Velliste et al. 2008 [1]; Hochberg et al. 2006 [2]; Pfurtscheller et al. 2000 [3]), restorative BCI systems aim at normalization of ­neurophysiologic activity that might facilitate motor recovery (e.g. Birbaumer et al. 2007, 2009 [4, 5]; Daly et al. 2008 [6]). In order to make assistive BCI systems work in daily life, high BCI communication speed is necessary, an issue that by now can only be achieved by invasive recordings of brain activity (e.g. via multi-unit arrays, MUA, or electrocorticogram, ECoG). Restorative BCI systems, in contrast, were developed as training tools based on non-invasive methods such as electro- or magnetoencephalography (EEG/MEG). More recently developed approaches use real-time functional magnetic resonance imaging (rtfMRI) or near-infrared ­spectroscopy (NIRS). Here, we provide an overview of the current state in the development and application of assistive and restorative BCI and introduce novel approaches to improve BCI control with brain stimulation such as transcranial direct current stimulation (tDCS). The outlook of using BCI in rehabilitation of stroke and neurotrauma is discussed.

Headache is among the most prevalent causes of disability worldwide. Non-pharmacologic interventions, including neuromodulation therapies, have been proposed in patients who are treatment resistant or intolerant to medications. To perform a systematic review on the use of transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) for the treatment of specific headache disorders (ie, migraine, tension, cluster, posttraumatic). Data sources: Ovid MEDLINE, Cochrane Central Register of Clinical Trials, Embase, Scopus, PsycINFO. All references were reviewed by 2 independent researchers (3039 abstracts, duplicates removed). Records were selected by inclusion criteria for participants (adults 18-65 with primary or secondary headaches), interventions (TMS and tDCS applied as headache treatment), comparators (sham or alternative standard of care), and study type (cohort, case-control, and randomized controlled trials [RCT]). Studies were assessed using the Cochrane Risk of Bias Tool and overall quality determined through the GRADE Tool. A structured synthesis was performed due to heterogeneity of participants and methods. Thirty-four studies were included: 16 rTMS, 6 TMS (excluding rTMS), and 12 tDCS. The majority investigated treatment for migraine (19/22 TMS, 8/12 tDCS). Quality of evidence ranged from very low to high. Of all TMS and tDCS modalities, rTMS is most promising with moderate evidence that it contributes to reductions in headache frequency, duration, intensity, abortive medication use, depression, and functional impairment. However, only few studies reported changes greater than sham treatment. Further high-quality RCTs with standardized protocols are required for each specific headache disorder to validate a treatment effect. Registration Number: PROSPERO 2017 CRD42017076232.

Traumatic brain injury (TBI) is a significant public health concern, often leading to long-lasting impairments in cognitive, motor and sensory functions. The rapid development of non-invasive systems has revolutionized the field of TBI rehabilitation by offering modern and effective interventions. This narrative review explores the application of non-invasive technologies, including electroencephalography (EEG), quantitative electroencephalography (qEEG), brain-computer interface (BCI), eye tracking, near-infrared spectroscopy (NIRS), functional near-infrared spectroscopy (fNIRS), magnetic resonance imaging (MRI), functional magnetic resonance imaging (fMRI), magnetoencephalography (MEG), and transcranial magnetic stimulation (TMS) in assessing TBI consequences, and repetitive transcranial magnetic stimulation (rTMS), low-level laser therapy (LLLT), neurofeedback, transcranial direct current stimulation (tDCS), transcranial alternative current stimulation (tACS) and virtual reality (VR) as therapeutic approaches for TBI rehabilitation. In pursuit of advancing TBI rehabilitation, this narrative review highlights the promising potential of non-invasive technologies. We emphasize the need for future research and clinical trials to elucidate their mechanisms of action, refine treatment protocols, and ensure their widespread adoption in TBI rehabilitation settings.

SummaryElectrophysiological studies in humans and animals suggest that noninvasive neurostimulation methods such as transcranial direct current stimulation (tDCS) can elicit long-lasting [1], polarity-dependent [2] changes in neocortical excitability. Application of tDCS can have significant and selective behavioral consequences that are associated with the cortical location of the stimulation electrodes and the task engaged during stimulation [3–8]. However, the mechanism by which tDCS affects human behavior is unclear. Recently, functional magnetic resonance imaging (fMRI) has been used to determine the spatial topography of tDCS effects [9–13], but no behavioral data were collected during stimulation. The present study is unique in this regard, in that both neural and behavioral responses were recorded using a novel combination of left frontal anodal tDCS during an overt picture-naming fMRI study. We found that tDCS had significant behavioral and regionally specific neural facilitation effects. Furthermore, faster naming responses correlated with decreased blood oxygen level-dependent (BOLD) signal in Broca's area. Our data support the importance of Broca's area within the normal naming network and as such indicate that Broca's area may be a suitable candidate site for tDCS in neurorehabilitation of anomic patients, whose brain damage spares this region.

Effects of transcranial electrical and magnetic stimulation on reciprocal inhibition in the human arm

To elucidate the involvement of motor pathways in konzo, 21 konzo subjects (mean age 22 years) underwent transcranial electrical stimulation (TES) in 1998. Fourteen konzo subjects (mean age 21 years) underwent transcranial magnetic stimulation (TMS) in 2000. Three subjects underwent both TES and TMS. Motor evoked potentials (MEPs) were recorded in the abductor pollicis brevis (APB) muscle with TES, and in the abductor digiti minimi (ADM) and tibialis anterior (TA) muscles with TMS. APB-MEPs were normal in 2 of 21 subjects and absent in 9; central conduction time (CCT) was prolonged in 10. Resting ADM-MEPs were absent in 9 of 14 subjects with clinically preserved upper limbs. Among these nine, seven subjects responded after facilitation. Most subjects (13 of 14) failed to show TA-MEPs. Of the subjects who underwent both types of stimulation, one had normal TES-MEP but abnormal ADM-MEP with TMS. These findings suggest involvement of both corticomotoneurons and motor descending pathways in konzo.

Chronic pain is debilitating and difficult to treat with pharmacotherapeutics alone. Consequently, exploring alternative treatment methods for chronic pain is essential. Noninvasive brain stimulation techniques, such as transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS) are increasingly being investigated for their neuropharmacological effects in the treatment of chronic pain. This review aims to examine and evaluate the present state of evidence regarding the use of tDCS and TMS in the treatment of chronic pain. Despite conflicting evidence in the early literature, evidence from recent rigorous research supports the use of tDCS and TMS in treating chronic pain conditions. For both tDCS and TMS, standardized stimulation parameters have been identified with the recommendation for repeated maintenance stimulation to ensure that the analgesic effect is sustained beyond discontinuation of therapy. Due to a lack of defined stimulation protocols, early findings on the efficacy of tDCS and TMS are mixed. Although the application of tDCS and TMS as pain relief approaches is still in its early stages, the introduction of standardized stimulation protocols is paving the way for more robust and informed research.

What Can Neuroimaging Tell Us About Aphasia?