Non-invasive Brain Stimulation Research Articles

Combination of non-invasive brain stimulation with mindfulness-based interventions for anxiety and depression symptoms: systematic review and meta-analysis of randomized controlled trials

Combination of non-invasive brain stimulation with mindfulness-based interventions for anxiety and depression symptoms: systematic review and meta-analysis of randomized controlled trials

Exploring whether home-based neuromodulation can boost the analgesic effects of exercise in people with knee osteoarthritis: protocol for a double-blinded, pilot randomised controlled trial

IntroductionKnee osteoarthritis (OA) represents a leading cause of disability globally. Exercise has been demonstrated to improve pain and function in people with knee OA. However, when in pain, commencement of...

State dependent motor cortex stimulation reveals distinct mechanisms for corticospinal excitability and cortical responses.

Transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation method that modulates brain activity by inducing electric fields in the brain. Real-time, state-dependent stimulation with TMS has shown that neural oscillation phase modulates corticospinal excitability. However, such motor-evoked potentials (MEPs) only indirectly reflect motor cortex activation and are unavailable at other brain regions of interest. The direct and secondary cortical effects of phase-dependent brain stimulation remain an open question. In this study, we recorded the cortical responses during single-pulse TMS using electroencephalography (EEG) concurrently with the MEP measurements in 20 healthy human volunteers (11 female). TMS was delivered at peak, rising, trough, and falling phases of mu (8-13 Hz) and beta (14-30 Hz) oscillations in the motor cortex. The cortical responses were quantified through TMS-evoked potential components N15, P50, and N100 as peak-to-peak amplitudes (P50-N15 and P50-N100). We further analyzed whether the pre-stimulus frequency band power was predictive of the cortical responses. We demonstrated that phase-specific targeting modulates cortical responses. The phase relationship between cortical responses was different for early and late responses. In addition, pre-TMS mu oscillatory power and phase significantly predicted both early and late cortical EEG responses in mu-specific targeting, indicating the independent causal effects of phase and power. However, only pre-TMS beta power significantly predicted the early and late TEP components during beta-specific targeting. Further analyses indicated distinct roles of mu and beta power on cortical responses. These findings provide insight to mechanistic understanding of neural oscillation states in cortical and corticospinal activation in humans.Significance Statement Understanding the effects of noninvasive neuromodulation on human brain provides valuable insights to its clinical utility. Brain state dependent stimulation helps us understand mechanisms leading to cortical responses and behavioral outcomes. Here we study the effects of the phase of ongoing oscillations in the motor cortex on cortical responses measured by electroencephalography. We also studied the relationship of phase preference between cortical responses and motor evoked potentials. Furthermore, we investigated the effects of the power of ongoing oscillations on cortical responses. These findings are important to understand the changes in biomarkers during state-dependent brain stimulation and their relationship to behavioral outcomes. At large, this helps the researchers to utilize state-dependent brain stimulation to enhance treatment efficacy.

Exploring Magnetic and Electrical Brain Stimulation in Parkinsonian Dyskinetic Monkeys.

Parkinson's disease (PD) chronic L-Dopa treatment often triggers motor complications, such as L-Dopa-induced dyskinesias (LID). LID are reported to be associated with abnormal glutamatergic activity between the striatum and primary motor cortex (M1), resulting in M1 hyperactivation. Beneficial noninvasive brain stimulation (NIBS) paradigms were reported to normalize glutamatergic activity. The objective of the present study was thus to set up a NIBS paradigm in parkinsonian monkeys to investigate motor behavior under basal conditions and with L-Dopa treatment-inducing dyskinesias. Motor behavior was investigated in five 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) dyskinetic female Macaca fascicularis monkey models of PD, allowing us to monitor the administration of NIBS and drugs. NIBS used were inhibitory protocols, that is, cathodal transcranial direct current stimulation (c-tDCS) and continuous theta-burst stimulation (cTBS). A procedure of three weeks was developed to progressively acclimate animals to the experimental conditions, equipment and noise of c-tDCS and cTBS before stimulating them with either vehicle or L-Dopa. One session of c-tDCS with L-Dopa yielded no effect, whereas five sessions briefly reduced LID but decreased the duration of L-Dopa anti-PD effects. cTBS alone improved (decreased) parkinsonian scores as compared to sham stimulation or vehicle alone. Two sessions of cTBS with L-Dopa decreased LID without affecting L-Dopa anti-PD effects. This is the first study testing c-tDCS and cTBS on the motor behavior of MPTP dyskinetic monkeys. As compared to medicated patients, MPTP monkeys offer the opportunity to evaluate NIBS after-effects in drug-free and LID conditions, which are critical in the search for new PD treatment.

Audiovestibular Dysfunction Related to Anti-Phospholipid Syndrome: A Systematic Review

Background: Anti-phospholipid syndrome (APS) has emerged as a significant issue in autoimmune diseases over recent decades. Its hallmark feature is thromboembolic events, potentially affecting any vascularized area including the microcirculation of the inner ear. Since the first case report of APS-related audiovestibular dysfunction described in 1993, numerous reports have explored the association between APS-related antibodies and audiovestibular dysfunction. These studies indicate a higher prevalence of APS-related antibodies in patients with sensorineural hearing loss compared to healthy controls. Unlike other idiopathic hearing loss disorders, audiovestibular dysfunction associated with APS may respond to appropriate treatments, highlighting the importance of timely recognition by clinicians to potentially achieve favorable outcomes. Therefore, this systematic review aims to consolidate current evidence on the characteristics, pathophysiology, assessment, and management of audiovestibular dysfunction linked to APS. Methods: This systematic review utilized electronic searches of the PubMed, Embase, ClinicalKey, Web of Science, and ScienceDirect online platforms. The initial search was performed on 27 January 2024, with the final update search completed on 20 June 2024. Results: Based on theoretical pathophysiology, anticoagulation emerges as a pivotal treatment strategy. Additionally, drawing from our preliminary data, we propose a modified protocol combining anticoagulants, steroids, and non-invasive brain stimulation to offer clinicians a novel therapeutic approach for managing these symptoms. Conclusions: Clinicians are encouraged to remain vigilant about the possibility of APS and its complex audiovestibular manifestations, as prompt intervention could stabilize audiovestibular function effectively.

Fluoxetine does not influence response to continuous theta burst stimulation in human motor cortex.

Selective serotonin reuptake inhibitors are thought to exert a clinical effect through various mechanisms, including through alteration in synaptic plasticity. Repetitive transcranial magnetic stimulation can induce temporary changes in synaptic excitability in cerebral cortex that resemble long-term potentiation and long-term depression that serve as a measure of synaptic plasticity invivo. A version of repetitive transcranial magnetic stimulation called continuous theta burst stimulation can induce inhibition of cortical excitability that can be measured through a motor evoked potential. Previous work has suggested that this response can be modulated by administration of selective serotonin reuptake inhibitors. Thirty-one healthy volunteers received both fluoxetine 20 mg and placebo in randomly ordered sessions, followed by spaced continuous theta burst stimulation to motor cortex. Changes in Motor Evoked Potentials were then recorded over 60 min. The response to spaced continuous theta burst stimulation did not differ significantly between fluoxetine and placebo sessions. Spaced continuous theta burst stimulation produced a paradoxical excitatory response in an unexpected number of participants. A single dose of fluoxetine 20 mg does not influence the response to continuous theta burst stimulation. Previous results suggesting an effect of selective serotonin reuptake inhibitors on inhibitory non-invasive brain stimulation protocols may be due to insufficiently large sample sizes.

Reproducible routes: reliably navigating the connectome to enrich personalized brain stimulation strategies

Non-invasive brain stimulation (NIBS) technologies, such as repetitive transcranial magnetic stimulation (rTMS), offer significant therapeutic potential for a growing number of neuropsychiatric conditions. Concurrent with the expansion of this field is the swift evolution of rTMS methodologies, including approaches to optimize stimulation site planning. Traditional targeting methods, foundational to early successes in the field and still widely employed today, include using scalp-based heuristics or integrating structural MRI co-registration to align the transcranial magnetic stimulation (TMS) coil with anatomical landmarks. Recent evidence, however, supports refining and personalizing stimulation sites based on the target's structural and/or functional connectivity profile. These connectomic approaches harness the network-wide neuromodulatory effects of rTMS to reach deeper brain structures while also enabling a greater degree of personalization by accounting for heterogenous network topology. In this study, we acquired baseline multimodal magnetic resonance (MRI) at two time points to evaluate the reliability and reproducibility of distinct connectome-based strategies for stimulation site planning. Specifically, we compared the intra-individual difference between the optimal stimulation sites generated at each time point for (1) functional connectivity (FC) guided targets derived from resting-state functional MRI and (2) structural connectivity (SC) guided targets derived from diffusion tensor imaging. Our findings suggest superior reproducibility of SC-guided targets. We emphasize the necessity for further research to validate these findings across diverse patient populations, thereby advancing the personalization of rTMS treatments.

Effectiveness of non-invasive brain stimulation on depressive symptoms targeting prefrontal cortex in functional magnetic resonance imaging studies: a combined systematic review and meta-analysis

Abstract The prefrontal cortex (PFC) is a critical non-invasive brain stimulation (NIBS) target for treating depression. However, the alterations of brain activations post-intervention remain inconsistent and the clinical moderators that could improve symptomatic effectiveness are unclear. The study aim was to systematically review the effectiveness of NIBS on depressive symptoms targeting PFC in functional magnetic resonance imaging (fMRI) studies. In our study, we delivered a combined activation likelihood estimation (ALE) meta-analysis and meta-regression. Until November 2020, three databases (PubMed, Web of Science, EMBASE) were searched and fourteen studies with a total sample size of 584 were included in the ALE meta-analysis; after NIBS, four clusters in left cerebrum revealed significant activation while two clusters in right cerebrum revealed significant deactivation (P < 0.001, cluster size > 150 mm3). Eleven studies were statistically reanalyzed for depressive symptoms pre-post active-NIBS and the pooled effect size was very large (d = 1.82, 95%CI [1.23, 2.40]); significant moderators causing substantial heterogeneity (Chi2 = 75.25, P < 0.01; I2 = 87%) were detected through subgroup analysis and univariate meta-regression. Multivariate meta-regression was then conducted accordingly and the model suggested good fitness (Q = 42.32, P < 0.01). In all, NIBS targeting PFC balanced three core depressive-related neurocognitive networks (the salience network, the default mode network and the central executive network); striatum played a central role and might serve as a candidate treatment biomarker; gender difference, treatment-resistant condition, comorbidity, treatment duration and localization all contributed to moderating depressive symptoms during NIBS. More high-quality, multi-center randomized controlled trails delivering personalized NIBS are urged for clinical practice in the future.

Safety of non-invasive brain stimulation in patients with implants: a computational risk assessment.

Non-invasive brain stimulation (NIBS) methodologies, such as transcranial electric (tES) are increasingly employed for therapeutic, diagnostic, or research purposes. The concurrent presence of active/passive implants can pose safety risks, affect the NIBS delivery, or generate confounding signals. A systematic investigation is required to understand the interaction mechanisms, quantify exposure, assess risks, and establish guidance for NIBS applications. We used measurements, simplified generic, and detailed anatomical modeling to: (i) systematically analyze exposure conditions with passive and active implants, considering local field enhancement, exposure dosimetry, tissue heating and neuromodulation, capacitive lead current injection, low-impedance pathways between electrode contacts, and insulation damage; (ii) identify risk metrics and efficient prediction strategies; (iii) quantify these metrics in relevant exposure cases and (iv) identify worst case conditions. Various aspects including implant design, positioning, scar tissue formation, anisotropy, and frequency were investigated. At typical tES frequencies, local enhancement of dosimetric exposure quantities can reach up to one order of magnitude for deep brain stimulation (DBS) and stereoelectroencephalography implants (more for elongated passive implants), potentially resulting in unwanted neuromodulation that can confound results but is still 2-3 orders of magnitude lower than active DBS. Under worst-case conditions, capacitive current injection in the active implants' lead can produce local exposures of similar magnitude as the passive field enhancement, while capacitive pathways between contacts are negligible. Above 10 kHz, applied current magnitudes increase, necessitating consideration of tissue heating. Furthermore, capacitive effects become more prominent, leading to current injection that can reach DBS-like levels. Adverse effects from abandoned/damaged leads in direct electrode vicinity cannot be excluded. Safety related concerns of tES application in the presence of implants are systematically identified and explored, resulting in specific and quantitative guidance and establishing basis for safety standards. Furthermore,several methods for reducing risks are suggested while acknowledging the limitations(see Sec. 4.5).

Strategies for applying noninvasive brain stimulation techniques to treat psychiatric disorders

With the continuous development of science and technology, medical science, and bioengineering technology, various neuromodulation techniques, such as electrical, magnetic, acoustic, and optical modalities, are rapidly emerging in the therapeutic regime of psychiatric disorders. How to choose the appropriate noninvasive brain stimulation techniques for different psychiatric disorders and their clinical features is becoming a practical dilemma in clinical setting. In this paper, by describing the complex pathogenesis of psychiatric disorders and the limitations of existing therapeutic approaches on psychiatric disorders, combining with the characteristics of different neuromodulation techniques, we propose a new strategy of combined noninvasive brain stimulation to intervene in psychiatric disorders: high-intensity stimulation modulating the whole brain without inducing epilepsy should be as the basic treatment of psychiatric disorders, applying low-intensity stimulation with the advantage of specific targets/brain regions to modulate the residual symptoms or/and single symptom, and for refractory and acute psychiatric disorders, ECT/MECT is preferred for rapid symptom control; different noninvasive brain stimulation techniques can be combined with pharmacological and psychotherapeutic treatments, which will provide a new idea for the future development of this field.

Balance of power: The choice between trial and participant numbers to optimise the detection of phase-dependent effects

Abstract The fields of neuroscience and psychology are currently in the midst of a so-called reproducibility crisis, with growing concerns regarding a history of weak effect sizes and low statistical power in much of the research published in these fields over the last few decades. Whilst the traditional approach for addressing this criticism has been to increase participant sample sizes, there are many research contexts in which the number of trials per participant may be of equal importance. The present study aimed to compare the relative importance of participants and trials in the detection of phase-dependent phenomena, which are measured across a range of neuroscientific contexts (e.g., neural oscillations, non-invasive brain stimulation). This was achievable within a simulated environment where one can manipulate the strength of this phase dependency in two types of outcome variables: one with normally distributed residuals (idealistic) and one comparable with motor-evoked potentials (an MEP-like variable). We compared the statistical power across thousands of experiments with the same number of sessions per experiment but with different proportions of participants and number of sessions per participant (30 participants × 1 session, 15 participants × 2 sessions, and 10 participants × 3 sessions), with the trials being pooled across sessions for each participant. These simulations were performed for both outcome variables (idealistic and MEP-like) and four different effect sizes (0.075—“weak,” 0.1—“moderate,” 0.125—“strong,” 0.15—“very strong”), as well as separate control scenarios with no true effect. Across all scenarios with (true) discoverable effects, and for both outcome types, there was a statistical benefit for experiments maximising the number of trials rather than the number of participants (i.e., it was always beneficial to recruit fewer participants but have them complete more trials). These findings emphasise the importance of obtaining sufficient individual-level data rather than simply increasing number of participants.

Effect of Dual-Site Non-Invasive Brain Stimulation on Upper-Limb Function After Stroke: A Systematic Review and Meta-Analysis.

Non-invasive brain stimulation (NIBS) has attracted significant attention as it has been proven to be effective in facilitating upper limb motor recovery in patients with stroke. This meta-analysis evaluates the efficacy of dual-site non-invasive brain stimulation (DS-NIBS) in improving upper extremity motor function after stroke. A PRISMA systematic search was conducted for randomized controlled trials. Two authors independently extracted data, and the quality of included studies was assessed. Ten studies were included in the current review. DS-NIBS demonstrated a significant effect on upper extremity motor function impairment. However, only two studies showed no clear effects of DS-tDCS on upper extremity motor function after stroke. Due to the limited number of studies, the effects of DS-NIBS remain inconclusive. This review found evidence for the relatively higher efficacy of DS-NIBS on post-stroke upper extremity motor function impairment, compared to the sham and SS-NIBS. Additionally, DS-TMS was found to generate better improvement than DS-tDCS.

Safety and efficacy of individual target transcranial magnetic stimulation to stimulate the most negative correlate of DLPFC-pgACC in the treatment of major depressive disorder: study protocol of a double-blind, randomised controlled trial

IntroductionMajor depressive disorder (MDD) is a common mental disorder that is characterised by high morbidity, high rates of relapse, high rates of disability and, in severe cases, suicide ideas or...

Restorative Treatments for Cervical Spinal Cord Injury, a Narrative Review.

A narrative review. To summarize relevant data from representative studies investigating upper limb restorative therapies for cervical spinal cord injury. Cervical spinal cord injury (SCI) is a debilitating condition resulting in tetraplegia, lifelong disability, and reduced quality of life. Given the dependence of all activities on hand function, patients with tetraplegia rank regaining hand function as one of their highest priorities. Recovery from cervical SCI is heterogeneous and often incomplete; currently, various novel therapies are under investigation to improve neurological function and eventually better quality of life in patients with tetraplegia. In this article, a narrative literature review was performed to identify treatment options targeting the restoration of function in patients with cervical SCI. Studies were included from available literature based on the availability of clinical data and whether they are applicable to restoration of arm and hand function in patients with cervical SCI. We describe relevant studies including indications and outcomes with a focus on arm and hand function. Different treatment modalities described include nerve transfers, tendon transfers, spinal cord stimulation, functional electrical stimulation, non-invasive brain stimulation, brain-machine interfaces and neuroprosthetics, stem cell therapy, and immunotherapy. As the authors' institution leads one of the largest clinical trials on nerve transfers for cervical SCI, we also describe how patients undergoing nerve transfers are managed and followed at our center. While complete recovery from cervical spinal cord injury may not be possible, novel therapies aimed at the restoration of upper limb motor function have made significant progress toward the realization of complete recovery.

Inhibitory effect of Transcranial Magnetic Stimulation (TMS) in the case of stroke: literature study

Background: Transcranial Magnetic Stimulation (TMS) is a form of non-invasive brain stimulation with the capacity to modulate cortical excitability. Low-frequency TMS (1 Hz) inhibits regional brain activity and allows contralateral cortical excitability through modulation of interhemispheric inhibition. Until now, research on low-frequency TMS that shows its inhibition on regional brain and the possibility of contralateral cortical stimulation is still very limited and not widely known. The purpose of this study was to determine the inhibitory effect of Transcranial Magnetic Stimulation (TMS) in post-stroke patients. Methods: Literature review was conducted to identify all articles that discuss the use of low-frequency TMS to determine the inhibitory effect of post-stroke patients on non-lesion areas. Databases from Hindawi, PubMed, Science Direct, and Cochrane with research types of pilot studies and randomized controlled trials published in the last 10 years by entering the keywords “Transcranial Magnetic Stimulation”, “Inhibition”, and “Stroke”. The research was conducted by systematically collecting, processing, and analyzing data. Results: Of the 505 articles identified, then selected according to the title there were 57 articles, obtained 10 articles that had abstracts according to the study. After that, the selection of articles according to the inclusion and exclusion criteria by reading the full article, there were 4 studies selected for review. 4 articles were included in this study showing motor improvement, increased functional ability, and cognitive improvement in post-stroke patients. Conclusion: TMS has beneficial effects on motor recovery in post-stroke patients with lasting effects.

Efficacy of non-invasive brain stimulation for post-stroke sleep disorders: a systematic review and meta-analysis.

This study aimed to systematically assess the clinical efficacy of non-invasive brain stimulation (NIBS) for treating post-stroke sleep disorders (PSSD). We conducted thorough literature search across multiple databases, including PubMed, Web of Science, EmBase, Cochrane Library, Scopus, China Biology Medicine (CBM); China National Knowledge Infrastructure (CNKI); Technology Periodical Database (VIP), and Wanfang Database, focusing on RCTs examining NIBS for PSSD. Meta-analyses were performed using RevMan 5.4 and Stata 14. Eighteen articles were reviewed, including 16 on repetitive Transcranial Magnetic Stimulation (rTMS), one on Theta Burst Stimulation (TBS), and two on transcranial Direct Current Stimulation (tDCS). Meta-analysis results indicated that rTMS within NIBS significantly improved the Pittsburgh Sleep Quality Index (PSQI) score (MD = -1.85, 95% CI [-2.99, -0.71], p < 0.05), the 17-item Hamilton Depression Rating Scale (HAMD-17) score [MD = -2.85, 95% CI (-3.40, -2.30), p < 0.05], and serum brain-derived neurotrophic factor (BDNF) levels [MD = 4.19, 95% CI (2.70, 5.69), p < 0.05], while reducing the incidence of adverse reactions [RR = 0.36, 95% CI (0.23, 0.55), p < 0.05]. TBS significantly improved the PSQI score in patients with PSSD (p < 0.05). Conversely, tDCS significantly improved the HAMD-17 score in PSSD patients [MD = -1.52, 95% CI (-3.41, -0.64), p < 0.05]. Additionally, rTMS improved sleep parameters, including Stage 2 sleep (S2%) and combined Stage 3 and 4 sleep (S3 + S4%) (p < 0.05), while tDCS improved total sleep time (TST) and sleep efficiency (SE) (p < 0.05).Subgroup analysis results indicated: (1) Both LF-rTMS and HF-rTMS improved PSQI scores (p < 0.05). (2) Both rTMS combined with medication and rTMS alone improved PSQI scores (p < 0.05). Compared to the sham/blank group, the rTMS group showed improvements in SE, sleep latency (SL), S1%, S3 + S4%, and REM sleep (REM%). The rTMS combined with medication group showed improved SL compared to the medication-only group (p < 0.05). NIBS effectively improves sleep quality, structure, depression levels, and BDNF levels in PSSD patients, while also being safe. Further investigations into the potential of NIBS in PSSD treatment may provide valuable insights for clinical applications. https://www.crd.york.ac.uk/prospero/, CRD42023485317.

Transcranial Focused Ultrasound Neuromodulation in Psychiatry: Main Characteristics, Current Evidence, and Future Directions

Non-invasive brain stimulation (NIBS) techniques are designed to precisely and selectively target specific brain regions, thus enabling focused modulation of neural activity. Among NIBS technologies, low-intensity transcranial focused ultrasound (tFUS) has emerged as a promising new modality. The application of tFUS can safely and non-invasively stimulate deep brain structures with millimetric precision, offering distinct advantages in terms of accessibility to non-cortical regions over other NIBS methods. However, to date, several tFUS aspects still need to be characterized; furthermore, there are only a handful of studies that have utilized tFUS in psychiatric populations. This narrative review provides an up-to-date overview of key aspects of this NIBS technique, including the main components of a tFUS system, the neuronavigational tools used to precisely target deep brain regions, the simulations utilized to optimize the stimulation parameters and delivery of tFUS, and the experimental protocols employed to evaluate the efficacy of tFUS in psychiatric disorders. The main findings from studies in psychiatric populations are presented and discussed, and future directions are highlighted.

Machine learning-optimized non-invasive brain stimulation and treatment response classification for major depression

Background/ObjectivesTranscranial direct current stimulation (tDCS) is a non-invasive brain stimulation intervention that shows promise as a potential treatment for depression. However, the clinical efficacy of tDCS varies, possibly due to individual differences in head anatomy affecting tDCS dosage. While functional changes in brain activity are more commonly reported in major depressive disorder (MDD), some studies suggest that subtle macroscopic structural differences, such as cortical thickness or brain volume reductions, may occur in MDD and could influence tDCS electric field (E-field) distributions. Therefore, accounting for individual anatomical differences may provide a pathway to optimize functional gains in MDD by formulating personalized tDCS dosage.MethodsTo address the dosing variability of tDCS, we examined a subsample of sixteen active-tDCS participants’ data from the larger ELECT clinical trial (NCT01894815). With this dataset, individualized neuroimaging-derived computational models of tDCS current were generated for (1) classifying treatment response, (2) elucidating essential stimulation features associated with treatment response, and (3) computing a personalized dose of tDCS to maximize the likelihood of treatment response in MDD.ResultsIn the ELECT trial, tDCS was superior to placebo (3.2 points [95% CI, 0.7 to 5.5; P = 0.01]). Our algorithm achieved over 90% overall accuracy in classifying treatment responders from the active-tDCS group (AUC = 0.90, F1 = 0.92, MCC = 0.79). Computed precision doses also achieved an average response likelihood of 99.981% and decreased dosing variability by 91.9%.ConclusionThese findings support our previously developed precision-dosing method for a new application in psychiatry by optimizing the statistical likelihood of tDCS treatment response in MDD.

Promising Neuroscience Methods in Exploring the Spatiotemporal Mechanisms underlying Speech Motor Control

Speech motor control is a complex neuromotor behavior that requires the combined efforts of feedforward control and feedback control subsystems. With the advent of neuroscience, multiple lines of research have explored the spatiotemporal mechanisms underlying this process. The purpose of this review was to point out several promising neuroscience methods and their unique values in enriching the speech motor control literature. We discussed the clinical value of noninvasive brain stimulation methods, and the theoretical value of invasive brain recording methods, as well as the predictive value of brain connectivity techniques. Based on prior findings, we propose a roadmap for future research, identifying structure-function coupling that supports speech motor control.

Syncing the brain's networks: dynamic functional connectivity shifts from temporal interference.

Temporal interference (TI) stimulation, an innovative non-invasive brain stimulation approach, has the potential to activate neurons in deep brain regions. However, the dynamic mechanisms underlying its neuromodulatory effects are not fully understood. This study aims to investigate the effects of TI stimulation on dynamic functional connectivity (dFC) in the motor cortex. 40 healthy adults underwent both TI and tDCS in a double-blind, randomized crossover design, with sessions separated by at least 48 h. The total stimulation intensity of TI is 4 mA, with each channel's intensity set at 2 mA and a 20 Hz frequency difference (2 kHz and 2.02 kHz). The tDCS stimulation intensity is 2 mA. Resting-state functional magnetic resonance imaging (rs-fMRI) data were collected before, during, and after stimulation. dFC was calculated using the left primary motor cortex (M1) as the region of interest (ROI) and analyzed using a sliding time-window method. A two-way repeated measures ANOVA (group × time) was conducted to evaluate the effects of TI and tDCS on changes in dFC. For CV of dFC, significant main effects of stimulation type (P = 0.004) and time (P < 0.001) were observed. TI showed lower CV of dFC than tDCS in the left postcentral gyrus (P < 0.001). TI-T2 displayed lower CV of dFC than TI-T1 in the left precentral gyrus (P < 0.001). For mean dFC, a significant main effect of time was found (P < 0.001). TI-T2 showed higher mean dFC than tDCS-T2 in the left postcentral gyrus (P = 0.018). Within-group comparisons revealed significant differences between time points in both TI and tDCS groups, primarily in the left precentral and postcentral gyri (all P < 0.001). Results were consistent across different window sizes. 20 Hz TI stimulation altered dFC in the primary motor cortex, leading to a significant decreasing variability and increasing mean connectivity strength in dFC. This outcome indicates that the 20 Hz TI frequency interacted with the motor cortex's natural resonance.