Corticospinal excitability

Short- and long-latency afferent inhibition (SAI and LAI respectively) are phenomenon whereby the motor evoked potential induced by transcranial magnetic stimulation (TMS) is inhibited by a sensory afferent volley consequent to nerve stimulation. It remains unclear whether dopamine participates in the genesis or modulation of SAI and LAI. The present study aimed to determine if SAI and LAI are modulated by levodopa (l-DOPA). In this placebo-controlled, double-anonymized study Apo-Levocarb (100 mg l-DOPA in combination with 25 mg carbidopa) and a placebo were administered to 32 adult males (mean age 24 ± 3 years) in two separate sessions...

PURPOSE: Motor evoked potential (MEP) characteristics are potential biomarkers of whether rehabilitation interventions drive motor recovery after stroke. The test-retest reliability of Transcranial Magnetic Stimulation (TMS) measurements in sub-acute stroke remains unclear. This study aims to determine the test-retest reliability of upper limb MEP measures elicited by non-neuronavigated transcranial magnetic stimulation in sub-acute-stroke. METHODS: In two identical data collection sessions, 1-3 days apart, TMS measures assessed: motor threshold (MT), amplitude, latency (MEP-L), silent period (SP), recruitment curve slope in the biceps brachii (BB), extensor carpi radialis (ECR), and abductor pollicis brevis (APB) muscles of paretic and non-paretic upper limbs...

BACKGROUND: Non-invasive brain stimulation techniques such as transcranial magnetic stimulation and transcranial direct current stimulation hold promise for inducing brain plasticity. However, their limited precision may hamper certain applications. In contrast, Transcranial Ultrasound Stimulation (TUS), known for its precision and deep brain targeting capabilities, requires further investigation to establish its efficacy in producing enduring effects for treating neurological and psychiatric disorders...

INTRODUCTION: Central nervous system excitability depends on the task performed, muscle group solicited, and contraction type. However, little is known on corticospinal and motoneuronal excitability measured during locomotor exercise. This study aimed at determining the reliability of motor-evoked potentials (MEP) and thoracic motor-evoked potentials (TMEP) in dynamic mode during unfatiguing and fatiguing cycling exercise. METHODS: Twenty-two participants completed four visits...

The ingestion of dietary cocoa flavanols acutely alters functions of the cerebral endothelium, but whether the effects of flavanols permeate beyond this to alter other brain functions remains unclear. Based on converging evidence, this work tested the hypothesis that cocoa flavanols would alter brain excitability in young healthy adults. In a randomised, cross-over, double-blinded, placebo-controlled design, transcranial magnetic stimulation was used to assess corticospinal and intracortical excitability before as well as 1 and 2 h post-ingestion of a beverage containing either high (695 mg flavanols, 150 mg (-)-epicatechin) or low levels (5 mg flavanols, 0 mg (-)-epicatechin) of cocoa flavanols...

BACKGROUND: Previous research has shown that noninvasive brain stimulation can be used to study how the central nervous system (CNS) prepares the execution of a motor task. However, these previous studies have been limited to a single muscle or single degree of freedom movements (e.g., wrist flexion). It is currently unclear if the findings of these studies generalize to multi-joint movements involving multiple muscles, which may be influenced by kinematic redundancy and muscle synergies...

INTRODUCTION: Brain computer interface-based action observation (BCI-AO) is a promising technique in detecting the user's cortical state of visual attention and providing feedback to assist rehabilitation. Peripheral nerve electrical stimulation (PES) is a conventional method used to enhance outcomes in upper extremity function by increasing activation in the motor cortex. In this study, we examined the effects of different pairings of peripheral nerve electrical stimulation (PES) during BCI-AO tasks and their impact on corticospinal plasticity...

Layer 5 neurons of the neocortex receive their principal inputs from layer 2/3 neurons. We seek to identify the nature and extent of the plasticity of these projections with motor learning. Using optogenetic and viral intersectional tools to selectively stimulate distinct neuronal subsets in rat primary motor cortex, we simultaneously record from pairs of corticospinal neurons associated with distinct features of motor output control: distal forelimb vs. proximal forelimb. Activation of Channelrhodopsin2-expressing layer 2/3 afferents onto layer 5 in untrained animals produces greater monosynaptic excitation of neurons controlling the proximal forelimb...

INTRODUCTION: Transcutaneous spinal cord stimulation (TSCS), a non-invasive form of spinal cord stimulation, has been shown to improve motor function in individuals living with spinal cord injury (SCI). However, the effects of different types of TSCS currents including direct current (DC-TSCS), alternating current (AC-TSCS), and spinal paired stimulation on the excitability of neural pathways have not been systematically investigated. The objective of this systematic review was to determine the effects of TSCS on the excitability of neural pathways in adults with non-progressive SCI at any level...

OBJECTIVES: We aimed to summarise and critically appraise the available evidence for the effect of age on responsiveness to non-invasive brain stimulation (NBS) paradigms delivered to the primary motor cortex. METHODS: Four databases (Medline, Embase, PsycINFO and Scopus) were searched from inception to February 7, 2023. Studies investigating age group comparisons and associations between age and neuroplasticity induction from NBS paradigms were included. Only studies delivering neuroplasticity paradigms to the primary motor cortex and responses measured via motor-evoked potentials (MEPs) in healthy adults were considered...

This study compared the acute hypoalgesic and neurophysiological responses to low-load resistance exercise with and without blood flow restriction (BFR), and free-flow, high-load exercise. Participants performed four experimental conditions where they completed baseline measures of pain pressure threshold (PPT), maximum voluntary force (MVF) with peripheral nerve stimulation to determine central and peripheral fatigue. Corticospinal excitability (CSE), corticospinal inhibition and short interval intracortical inhibition (SICI) were estimated with transcranial magnetic stimulation...

Spinal cord injury (SCI) is a debilitating condition currently lacking treatment. Severe SCI causes the loss of most supraspinal inputs and neuronal activity caudal to the injury, which, coupled with the limited endogenous capacity for spontaneous regeneration, can lead to complete functional loss even in anatomically incomplete lesions. We hypothesized that transplantation of mature dorsal root ganglia (DRG), genetically modified to express the NaChBac sodium channel, could serve as a therapeutic option for functionally complete SCI...

Prior studies suggest resistance exercise as a potential form of motor learning due to task-specific corticospinal responses observed in single sessions of motor skill and resistance training. While existing literature primarily focuses on upper limb muscles, revealing a task-dependent nature in eliciting corticospinal responses, our aim was to investigate such responses after a single session of lower limb motor skill and resistance training. Twelve participants engaged in a visuomotor force tracking task, self-paced knee extensions, and a control task...

Motor imagery is a cognitive process involving the simulation of motor actions without actual movements. Despite the reported positive effects of motor imagery training on motor function, the underlying neurophysiological mechanisms have yet to be fully elucidated. Therefore, the purpose of the present study was to investigate how sustained tonic finger-pinching motor imagery modulates sensorimotor integration and corticospinal excitability using short-latency afferent inhibition (SAI) and single-pulse transcranial magnetic stimulation (TMS) assessments, respectively...

This scientific commentary refers to 'Explicit and implicit motor simulations are impaired in individuals with aphantasia', by Dupont   et al . (https://doi.org/10.1093/braincomms/fcae072) in Brain Communications .

Individuals with aphantasia report having difficulties or an inability to generate visual images of objects or events. So far, there is no evidence showing that this condition also impacts the motor system and the generation of motor simulations. We probed the neurophysiological marker of aphantasia during explicit and implicit forms of motor simulation, i.e. motor imagery and action observation, respectively. We tested a group of individuals without any reported imagery deficits (phantasics) as well as a group of individuals self-reporting the inability to mentally simulate images or movements (aphantasics)...

Transcranial static magnetic field stimulation (tSMS) is a non-invasive brain stimulation technique that is portable and easy to use. Long-term, home-based treatments with tSMS of the supplementary motor area (SMA) are promising for movement disorders and other brain diseases. The aim of the present work was to investigate the potential of SMA-tSMS for reducing corticospinal excitability. We completed an open pilot study in which twenty right-handed healthy subjects (8 females; age: 31.3 ± 5...

People experiencing kinesiophobia are more likely to develop persistent disabilities and chronic pain. However, the impact of kinesiophobia on the motor system remains poorly understood. We investigated whether kinesiophobia could modulate shoulder pain-induced changes in (1) kinematic parameters and muscle activation during functional movement and (2) corticospinal excitability. Thirty healthy, pain-free subjects took part in the study. Shoulder, elbow, and finger kinematics, as well as electromyographic activity of the upper trapezius and anterior deltoid muscles, were recorded while subjects performed a pointing task before and during pain induced by capsaicin at the shoulder...

INTRODUCTION: Spasticity is a frequent disabling consequence following a stroke. Local muscle vibrations (LMVs) have been proposed as a treatment to address this problem. However, little is known about their clinical and neurophysiological impacts when used repeatedly during the subacute phase post-stroke. This project aims to evaluate the effects of a 6-week LMV protocol on the paretic limb on spasticity development in a post-stroke subacute population. METHODS AND ANALYSIS: This is an interventional, controlled, randomised, single-blind (patient) trial...

Motor sequence learning gradually quickens reaction time, suggesting that sequence learning alters motor preparation processes. Interestingly, evidence has shown that preparing sequence movements decreases short intracortical inhibition (SICI) in the contralateral motor cortex (M1), but also that sequence learning alters motor preparation processes in both the contralateral and ipsilateral M1s. Therefore, one possibility is that sequence learning alters the SICI decreases occurring during motor preparation in bilateral M1s...