Low-intensity contralesional electrical theta burst stimulation modulates ipsilesional excitability and enhances stroke recovery

The Effect of Intermittent Theta Burst Stimulation for Post-Stroke Lower Limb Motor Recovery: A Systematic Review and Meta-Analysis

BackgroundIntermittent theta burst stimulation (iTBS) appears to be a potential intervention for enhancing motor recovery in post-stroke. However, the optimal parameters of iTBS protocol for lower limb dysfunction is ambiguous.ObjectiveTo evaluate the efficacy of iTBS in treating lower limb motor impairment after stroke and to explore the optimal stimulation parameters.MethodsRelevant randomized controlled trials (RCTs) were retrieved from seven databases from their inception to May 2024. We defined primary outcomes as Fugl-Meyer Assessment for Lower Extremity (FMA-LE) and Berg Balance Scale (BBS). Subgroup analyses included stroke stage, stimulation sites, dosages and treatment sessions.ResultsThe study results indicated that compared with the sham iTBS group, the iTBS group showed a significant improvement in lower limb motor recovery, balance, gait and activity of daily living (ADL). No significant effect was found in the Motor Evoked Potential amplitude. Subgroup analysis demonstrated that cerebellar iTBS had a therapeutic effect on subacute stroke patients. Furthermore, administrating 1200 pulses per session for a minimum of 15 sessions of iTBS intervention could significantly improve the balance and ADL performance.ConclusioniTBS could enhance lower limb motor function, improving the quality of life in subacute stroke patients with relatively high safety.

Effects of intermittent theta burst stimulation on upper limb motor recovery in early stroke patients: an fNIRS study

Objective

To explore the recovery of upper limb motor function and the changes in cortical functional connectivity in patients with early subcortical small infarcts accompanied by severe upper limb motor dysfunction (PESSUM) after intermittent theta burst stimulation (iTBS) via functional near-infrared spectroscopy (fNIRS) and to explore the related mechanisms.

Methods

We enrolled 56 subcortical ischemic stroke patients with FMA-UE ≤28 and randomly assigned them to receive either genuine (TG, n = 29) or sham (CG, n = 23) iTBS plus standard rehabilitation over 8 days. fNIRS was used to monitor cerebral HbO, HbD, and HbT concentrations, and RSFC changes were analyzed. The FMA-UE and MBI scores were used to evaluate upper limb motor function and daily activities. Intergroup comparisons were conducted using independent samples t tests, whereas intragroup comparisons were performed using paired samples t tests or Mann-Whitney U tests. The trend of the RSFC changes was analyzed via repeated-measures Analysis of Variance (ANOVA).

Results

Both groups showed significant improvements in FMA-UE and MBI scores postintervention (p < 0.001). The TG had higher MBI scores than the CG (p = 0.005). fNIRS revealed accelerated cyclical changes in cortical activity in the TG.

Conclusion

iTBS significantly improved motor function and daily living ability in stroke patients, supporting a role for iTBS in promoting neural repair by accelerating cortical recovery cycles. This study provides evidence that iTBS is an effective rehabilitation strategy poststroke.

Clinical trial registration

https://www.chictr.org.cn/showproj.html?proj=169674, ChiCTR2200060955.

Quantum Computing in the Realm of Neurosurgery

Quantum computing leverages the principles of quantum mechanics to provide unprecedented computational power by processing data in a fundamentally different way from classical binary computers. Quantum computers use "qubits" which superimpose 0 and 1. Because qubits can exist in multiple states at the same time, quantum computers can perform "quantum parallelism" wherein data are processed simultaneously rather than sequentially. The quantum parallelism is what enables the computer to have exponentially larger processing capabilities and consider all potential outcomes simultaneously to derive solutions. Our study aims to explore aspects of neurosurgery through which quantum computing could improve patient outcomes and enhance quality of care. Quantum computing has the potential for future applications in neuroprosthetics, neurostimulation, surgical precision, diagnosis, and patient privacy and security. It promises improved patient outcomes, enhanced surgical precision, and personalized healthcare delivery. With its inherent sensitivity and precision, quantum computing could advance the understanding of disease processes and development, providing neurosurgeons with deeper insight into patient pathologies. Challenges such as biocompatibility, cost, and ethical considerations remain significant barriers to integrating the technology into neurosurgical practice. Addressing these challenges will be crucial for realizing the transformative potential of quantum computing in advancing neurosurgical care and improving clinical outcomes.

Therapeutic ultrasound: an innovative approach for targeting neurological disorders affecting the basal ganglia

The basal ganglia are involved in motor control and action selection, and their impairment manifests in movement disorders such as Parkinson's disease (PD) and dystonia, among others. The complex neuronal circuitry of the basal ganglia is located deep inside the brain and presents significant treatment challenges. Conventional treatment strategies, such as invasive surgeries and medications, may have limited effectiveness and may result in considerable side effects. Non-invasive ultrasound (US) treatment approaches are becoming increasingly recognized for their therapeutic potential for reversibly permeabilizing the blood-brain barrier (BBB), targeting therapeutic delivery deep into the brain, and neuromodulation. Studies conducted on animals and early clinical trials using ultrasound as a therapeutic modality have demonstrated promising outcomes for controlling symptom severity while preserving neural tissue. These results could improve the quality of life for patients living with basal ganglia impairments. This review article explores the therapeutic frontiers of ultrasound technology, describing the brain mechanisms that are triggered and engaged by ultrasound. We demonstrate that this cutting-edge method could transform the way neurological disorders associated with the basal ganglia are managed, opening the door to less invasive and more effective treatments.

Pilot study of using transcranial temporal interfering theta-burst stimulation for modulating motor excitability in rat

Transcranial temporal interference stimulation (tTIS) is a promising brain stimulation method that can target deep brain regions by delivering an interfering current from surface electrodes. Most instances of tTIS stimulate the brain with a single-frequency sinusoidal waveform generated by wave interference. Theta burst stimulation is an effective stimulation scheme that can modulate neuroplasticity by generating long-term potentiation- or depression-like effects. To broaden tTIS application, we developed a theta burst protocol using tTIS technique to modulate neuroplasticity in rats. Two cannula electrodes were unilaterally implanted into the intact skull over the primary motor cortex. Electrical field of temporal interference envelopes generated by tTIS through cannula electrodes were recorded from primary motor cortex. Theta burst schemes were characterized, and motor activation induced by the stimulation was also evaluated simultaneously by observing electromyographic signals from the corresponding brachioradialis muscle. After validating the stimulation scheme, we further tested the modulatory effects of theta burst stimulation delivered by tTIS and by conventional transcranial electrical stimulation on primary motor cortex excitability. Changes in the amplitude of motor evoked potentials, elicited when the primary motor cortex was activated by electrical pulses, were measured before and after theta burst stimulation by both techniques. Significant potentiation and suppression were found at 15 to 30 min after the intermittent and continuous theta burst stimulation delivered using tTIS, respectively. However, comparing to theta burst stimulations delivered using conventional form of transcranial electrical stimulation, using tTIS expressed no significant difference in modulating motor evoked potential amplitudes. Sham treatment from both methods had no effect on changing the motor evoked potential amplitude. The present study demonstrated the feasibility of using tTIS to achieve a theta burst stimulation scheme for motor cortical neuromodulation. These findings also indicated the future potential of using tTIS to carry out theta burst stimulation protocols in deep-brain networks for modulating neuroplasticity.

Cholinergic modulation of interhemispheric inhibition in the mouse motor cortex

Interhemispheric inhibition of the homotopic motor cortex is believed to be effective for accurate unilateral motor function. However, the cellular mechanisms underlying interhemispheric inhibition during unilateral motor behavior remain unclear. Furthermore, the impact of the neuromodulator acetylcholine on interhemispheric inhibition and the associated cellular mechanisms are not well understood. To address this knowledge gap, we conducted recordings of neuronal activity from the bilateral motor cortex of mice during the paw-reaching task. Subsequently, we analyzed interhemispheric spike correlation at the cell-pair level, classifying putative cell types to explore the underlying cellular circuitry mechanisms of interhemispheric inhibition. We found a cell-type pair-specific enhancement of the interhemispheric spike correlation when the mice were engaged in the reaching task. We also found that the interhemispheric spike correlation was modulated by pharmacological acetylcholine manipulation. The local field responses to contralateral excitation differed along the cortical depths, and muscarinic receptor antagonism enhanced the inhibitory component of the field response in deep layers. The muscarinic subtype M2 receptor is predominantly expressed in deep cortical neurons, including GABAergic interneurons. These results suggest that GABAergic interneurons expressing muscarinic receptors in deep layers mediate the neuromodulation of interhemispheric inhibition in the homotopic motor cortex.

Intrinsic Plasticity Mechanisms of Repetitive Transcranial Magnetic Stimulation

Repetitive transcranial magnetic stimulation (rTMS) has become an increasingly popular tool to modulate neural excitability and induce neural plasticity in clinical and preclinical models; however, the physiological mechanisms in which it exerts these effects remain largely unknown. To date, studies have primarily focused on characterizing rTMS-induced changes occurring at the synapse, with little attention given to changes in intrinsic membrane properties. However, accumulating evidence suggests that rTMS may induce its effects, in part, via intrinsic plasticity mechanisms, suggesting a new and potentially complementary understanding of how rTMS alters neural excitability and neural plasticity. In this review, we provide an overview of several intrinsic plasticity mechanisms before reviewing the evidence for rTMS-induced intrinsic plasticity. In addition, we discuss a select number of neurological conditions where rTMS-induced intrinsic plasticity has therapeutic potential before speculating on the temporal relationship between rTMS-induced intrinsic and synaptic plasticity.

Effects of individual metabolic brain network changes co-affected by T2DM and aging on the probabilities of T2DM: protective and risk factors

Neuroimaging markers for risk and protective factors related to type 2 diabetes mellitus are critical for clinical prevention and intervention. In this work, the individual metabolic brain networks were constructed with Jensen-Shannon divergence for 4 groups (elderly type 2 diabetes mellitus and healthy controls, and middle-aged type 2 diabetes mellitus and healthy controls). Regional network properties were used to identify hub regions. Rich-club, feeder, and local connections were subsequently obtained, intergroup differences in connections and correlations between them and age (or fasting plasma glucose) were analyzed. Multinomial logistic regression was performed to explore effects of network changes on the probability of type 2 diabetes mellitus. The elderly had increased rich-club and feeder connections, and decreased local connection than the middle-aged among type 2 diabetes mellitus; type 2 diabetes mellitus had decreased rich-club and feeder connections than healthy controls. Protective factors including glucose metabolism in triangle part of inferior frontal gyrus, metabolic connectivity between triangle of the inferior frontal gyrus and anterior cingulate cortex, degree centrality of putamen, and risk factors including metabolic connectivities between triangle of the inferior frontal gyrus and Heschl's gyri were identified for the probability of type 2 diabetes mellitus. Metabolic interactions among critical brain regions increased in type 2 diabetes mellitus with aging. Individual metabolic network changes co-affected by type 2 diabetes mellitus and aging were identified as protective and risk factors for the likelihood of type 2 diabetes mellitus, providing guiding evidence for clinical interventions.

Blood-Glucose-Powered Metabolic Fuel Cell for Self-Sufficient Bioelectronics

Currently available bioelectronic devices consume too much power to be continuously operated on rechargeable batteries, and are often powered wirelessly, with attendant issues regarding reliability, convenience, and mobility. Thus, the availability of a robust, self-sufficient, implantable electrical power generator that works under physiological conditions would be transformative for many applications, from driving bioelectronic implants and prostheses to programing cellular behavior and patients' metabolism. Here, capitalizing on a new copper-containing, conductively tuned 3D carbon nanotube composite, an implantable blood-glucose-powered metabolic fuel cell is designed that continuously monitors blood-glucose levels, converts excess glucose into electrical power during hyperglycemia, and produces sufficient energy (0.7 mW cm^-2 , 0.9 V, 50 mm glucose) to drive opto- and electro-genetic regulation of vesicular insulin release from engineered beta cells. It is shown that this integration of blood-glucose monitoring with elimination of excessive blood glucose by combined electro-metabolic conversion and insulin-release-mediated cellular consumption enables the metabolic fuel cell to restore blood-glucose homeostasis in an automatic, self-sufficient, and closed-loop manner in an experimental model of type-1 diabetes.

Excitatory-Inhibitory Homeostasis and Diaschisis: Tying the Local and Global Scales in the Post-stroke Cortex

Maintaining a balance between excitatory and inhibitory activity is an essential feature of neural networks of the neocortex. In the face of perturbations in the levels of excitation to cortical neurons, synapses adjust to maintain excitatory-inhibitory (EI) balance. In this review, we summarize research on this EI homeostasis in the neocortex, using stroke as our case study, and in particular the loss of excitation to distant cortical regions after focal lesions. Widespread changes following a localized lesion, a phenomenon known as diaschisis, are not only related to excitability, but also observed with respect to functional connectivity. Here, we highlight the main findings regarding the evolution of excitability and functional cortical networks during the process of post-stroke recovery, and how both are related to functional recovery. We show that cortical reorganization at a global scale can be explained from the perspective of EI homeostasis. Indeed, recovery of functional networks is paralleled by increases in excitability across the cortex. These adaptive changes likely result from plasticity mechanisms such as synaptic scaling and are linked to EI homeostasis, providing a possible target for future therapeutic strategies in the process of rehabilitation. In addition, we address the difficulty of simultaneously studying these multiscale processes by presenting recent advances in large-scale modeling of the human cortex in the contexts of stroke and EI homeostasis, suggesting computational modeling as a powerful tool to tie the meso- and macro-scale processes of recovery in stroke patients.

Continuous Theta-Burst Stimulation Intensity Dependently Facilitates Motor-Evoked Potentials Following Focal Electrical Stimulation of the Rat Motor Cortex

Although theta-burst stimulation (TBS) is known to differentially modify motor cortical excitability according to stimulus conditions in humans, whether similar effects can be seen in animals, in particular rats, remains to be defined. Given the importance of experimental rat models for humans, this study explored this stimulation paradigm in rats. Specifically, this study aimed to explore corticospinal excitability after TBS in anesthetized animals to confirm its comparability with human results. Both inhibition-facilitation configurations using paired electrical stimulation protocols and the effects of the TBS paradigm on motor-evoked potentials (MEPs) in rat descending motor pathways were assessed. Paired-stimulation MEPs showed inhibition [interstimulus interval (ISI): 3 ms] and facilitation (11 ms) patterns under medetomidine/midazolam/butorphanol (MMB) anesthesia. Furthermore, while ketamine and xylazine (K/X) anesthesia completely blocked facilitation at 11-ms ISI, inhibition at a 3-ms ISI was preserved. Continuous and intermittent TBS strongly facilitated MEPs depending on stimulus intensity, persisting for up to 25 min under both MMB and K/X anesthesia. These findings are similar to the intracortical inhibition and facilitation observed in the human motor cortex using paired-pulse magnetic stimulation, particularly the glutamate-mediated facilitation phase. However, different TBS facilitatory mechanisms occur in the rat motor cortex. These different TBS facilitatory mechanisms affect the comparability and interpretations of TBS between rat and human models.