Direct corticospinal pathways contribute to neuromuscular control of perturbed stance

2006 ◽  
Vol 101 (2) ◽  
pp. 420-429 ◽  
Author(s):  
Wolfgang Taube ◽  
Martin Schubert ◽  
Markus Gruber ◽  
Sandra Beck ◽  
Michael Faist ◽  
...  
Keyword(s):  
Magnetic Stimulation ◽  
Evoked Potential ◽  
Cortical Excitability ◽  
Motor Evoked Potential ◽  
Neuromuscular Control ◽  
H Reflex ◽  
Compensatory Response ◽  
Long Latency Responses ◽  
Long Latency ◽  
Posterior Translation

The antigravity soleus muscle (Sol) is crucial for compensation of stance perturbation. A corticospinal contribution to the compensatory response of the Sol is under debate. The present study assessed spinal, corticospinal, and cortical excitability at the peaks of short- (SLR), medium- (MLR), and long-latency responses (LLR) after posterior translation of the feet. Transcranial magnetic stimulation (TMS) and peripheral nerve stimulation were individually adjusted so that the peaks of either motor evoked potential (MEP) or H reflex coincided with peaks of SLR, MLR, and LLR, respectively. The influence of specific, presumably direct, corticospinal pathways was investigated by H-reflex conditioning. When TMS was triggered so that the MEP arrived in the Sol at the same time as the peaks of SLR and MLR, EMG remained unaffected. Enhanced EMG was observed when the MEP coincided with the LLR peak ( P < 0.001). Similarly, conditioning of the H reflex by subthreshold TMS facilitated H reflexes only at LLR ( P < 0.001). The earliest facilitation after perturbation occurred after 86 ms. The TMS-induced H-reflex facilitation at LLR suggests that increased cortical excitability contributes to the augmentation of the LLR peaks. This provides evidence that the LLR in the Sol muscle is at least partly transcortical, involving direct corticospinal pathways. Additionally, these results demonstrate that ∼86 ms after perturbation, postural compensatory responses are cortically mediated.

Reduced cortical excitability in depression

1999 ◽  
Vol 174 (5) ◽  
pp. 449-454 ◽  
Author(s):  
P. M. Shajahan ◽  
M. F. Glabus ◽  
P. A. Gooding ◽  
P. J. Shah ◽  
K. P. Ebmeier
Keyword(s):  
Magnetic Stimulation ◽  
Evoked Potential ◽  
Primary Motor Cortex ◽  
Cortical Excitability ◽  
Motor Evoked Potential ◽  
Abductor Pollicis Brevis ◽  
Post Exercise ◽  
Significant Difference ◽  
Dsm Iv ◽  
The Mean

BackgroundIn healthy controls, preactivation of muscles by exercise results in enhanced motor-evoked potential (MEP) responses to transcranial magnetic stimulation (TMS).AimsWe tested the hypothesis that medicated, depressed patients would show reduced post-exercise MEP facilitation compared with controls.MethodTen patients with DSM-IV depression (two male, eight female) and ten controls (three male, seven female) participated. MEPs were elicited at rest, then after exercising the contralateral abductor pollicis brevis muscle, using TMS of the primary motor cortex.ResultsThe mean MEP amplitude recorded after exercise (expressed as a percentage of baseline) was 210% in controls and 130% in patients. There was a significant difference in post-exercise MEP between patients and controls (P=0.03).ConclusionsPost-exercise MEP facilitation was demonstrated in controls but not in patients. This supports the hypothesis that the modulation of cortical excitability may be impaired in depression.

scholarly journals Modulation of the Corticomotor Excitability by Repetitive Peripheral Magnetic Stimulation on the Median Nerve in Healthy Subjects

2021 ◽  
Vol 15 ◽  
Author(s):  
Yanbing Jia ◽  
Xiaoyan Liu ◽  
Jing Wei ◽  
Duo Li ◽  
Chun Wang ◽  
...  
Keyword(s):  
Peripheral Nerve ◽  
Healthy Subjects ◽  
Magnetic Stimulation ◽  
Evoked Potential ◽  
Sham Group ◽  
Motor Evoked Potential ◽  
Dominant Hand ◽  
Corticomotor Excitability ◽  
Hand Dexterity ◽  
Stimulation Group

Objective: We aimed to examine the effects of repetitive peripheral nerve magnetic stimulation (rPNMS) on the excitability of the contralateral motor cortex and motor function of the upper limb in healthy subjects.Methods: Forty-six healthy subjects were randomly assigned to either a repetitive peripheral nerve magnetic stimulation group (n = 23) or a sham group (n = 23). The repetitive peripheral nerve magnetic stimulation group received stimulation using magnetic pulses at 20 Hz, which were applied on the median nerve of the non-dominant hand, whereas the sham group underwent the same protocol without the stimulation output. The primary outcome was contralateral transcranial magnetic stimulation (TMS)-induced corticomotor excitability for the abductor pollicis brevis of the stimulated hand in terms of resting motor threshold (rMT), the slope of recruitment curve, and peak amplitude of motor evoked potential (MEP), which were measured at baseline and immediately after each session. The secondary outcomes were motor hand function including dexterity and grip strength of the non-dominant hand assessed at baseline, immediately after stimulation, and 24 h post-stimulation.Results: Compared with the sham stimulation, repetitive peripheral nerve magnetic stimulation increased the peak motor evoked potential amplitude immediately after the intervention. The repetitive peripheral nerve magnetic stimulation also increased the slope of the recruitment curve immediately after intervention and enhanced hand dexterity after 24 h. However, the between-group difference for the changes was not significant. The significant changes in hand dexterity and peak amplitude of motor evoked potential after repetitive peripheral nerve magnetic stimulation were associated with their baseline value.Conclusions: Repetitive peripheral nerve magnetic stimulation may modulate the corticomotor excitability together with a possible lasting improvement in hand dexterity, indicating that it might be helpful for clinical rehabilitation.

scholarly journals The effects of forearm position and contraction intensity on cortical and spinal excitability during a submaximal force steadiness task of the elbow flexors

2020 ◽  
Vol 123 (2) ◽  
pp. 522-528
Author(s):  
Alexandra F. Yacyshyn ◽  
Samantha Kuzyk ◽  
Jennifer M. Jakobi ◽  
Chris J. McNeil
Keyword(s):  
Evoked Potential ◽  
Biceps Brachii ◽  
Cortical Excitability ◽  
Motor Evoked Potential ◽  
Elbow Flexor ◽  
Elbow Flexors ◽  
Neural Excitability ◽  
Force Steadiness ◽  
Maximal Force ◽  
Spinal Excitability

Elbow flexor force steadiness is less with the forearm pronated (PRO) compared with neutral (NEU) or supinated (SUP) and may relate to neural excitability. Although not tested in a force steadiness paradigm, lower spinal and cortical excitability was observed separately for biceps brachii in PRO, possibly dependent on contractile status at the time of assessment. This study aimed to investigate position-dependent changes in force steadiness as well as spinal and cortical excitability at a variety of contraction intensities. Thirteen males (26 ± 7 yr; means ± SD) performed three blocks (PRO, NEU, and SUP) of 24 brief (~6 s) isometric elbow flexor contractions (5, 10, 25 or 50% of maximal force). During each contraction, transcranial magnetic stimulation or transmastoid stimulation was delivered to elicit a motor-evoked potential (MEP) or cervicomedullary motor-evoked potential (CMEP), respectively. Force steadiness was lower in PRO compared with NEU and SUP ( P ≤ 0.001), with no difference between NEU and SUP. Similarly, spinal excitability (CMEP/maximal M wave) was lower in PRO than NEU (25 and 50% maximal force; P ≤ 0.010) and SUP (all force levels; P ≤ 0.004), with no difference between NEU and SUP. Cortical excitability (MEP/CMEP) did not change with forearm position ( P = 0.055); however, a priori post hoc testing for position showed excitability was 39.8 ± 38.3% lower for PRO than NEU at 25% maximal force ( P = 0.006). The data suggest that contraction intensity influences the effect of forearm position on neural excitability and that reduced spinal and, to a lesser extent, cortical excitability could contribute to lower force steadiness in PRO compared with NEU and SUP. NEW & NOTEWORTHY To address conflicting reports about the effect of forearm position on spinal and cortical excitability of the elbow flexors, we examine the influence of contraction intensity. For the first time, excitability data are considered in a force steadiness context. Motoneuronal excitability is lowest in pronation and this disparity increases with contraction intensity. Cortical excitability exhibits a similar pattern from 5 to 25% of maximal force. Lower corticospinal excitability likely contributes to relatively poor force steadiness in pronation.

Design and analysis of motor-evoked potential data in pediatric neurobehavioral disorder investigations

2012 ◽  
Author(s):  
Donald L. Gilbert
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Research Methods ◽  
Magnetic Stimulation ◽  
Evoked Potential ◽  
Motor Evoked Potential ◽  
Experimental Designs ◽  
Future Research ◽  
Paired Pulse ◽  
Practical Guidance

This article discusses how transcranial magnetic stimulation (TMS) can be used to study the pathophysiological substrata of pediatric neurological and neurobehavioural disorders and to provide practical guidance for future research. It outlines the substantial challenges inherent in studying in vivo the neurobiology of pediatric neurobehavioural disorders, such as safety, quantitative versus categorical measures, and challenges in correlational studies. It discusses ways in which TMS generates quantitative measures that may function as endophenotypes for neurobehavioural disorders. Combining TMS with other modalities may also be informative. Single- and paired-pulse TMS is safe and well tolerated in children. The application of rigorous experimental designs and a combination of TMS with other research methods may increase the knowledge of pathophysiology and treatment of pediatric neurobehavioural disorders.

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