Increased probability of repetitive spinal motoneuron activation by transcranial magnetic stimulation after muscle fatigue in healthy subjects

2012 ◽  
Vol 112 (5) ◽  
pp. 832-840 ◽  
Author(s):  
Birgit Andersen ◽  
Ulrik Ascanius Felding ◽  
Christian Krarup
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Healthy Subjects ◽  
Magnetic Stimulation ◽  
Motor Evoked Potential ◽  
Excitatory Input ◽  
Observation Time ◽  
Voluntary Activity ◽  
Abductor Digiti Minimi ◽  
Motor Unit Activation ◽  
Fatiguing Exercise

Triple stimulation technique (TST) has previously shown that transcranial magnetic stimulation (TMS) fails to activate a proportion of spinal motoneurons (MNs) during motor fatigue. The depression in size of the TST response, but no attenuation of the conventional motor-evoked potential, suggested increased probability of repetitive spinal MN activation during exercise, even if some MNs failed to discharge by the brain stimulus. Here we used a modified TST [quadruple stimulation (QuadS) and quintuple stimulation (QuintS)] to examine the influence of fatiguing exercise on second and third MN discharges after a single TMS in healthy subjects. This method allows an estimation of the percentage of double and triple discharging MNs. Following a sustained contraction of the abductor digiti minimi muscle at 50% maximal force maintained to exhaustion, the size of QuadS and QuintS responses increased markedly, reflecting that a greater proportion of spinal MNs was activated two or three times by the transcranial stimulus. The size of QuadS responses did not return to precontraction levels during 10-min observation time, indicating long-lasting increase in excitatory input to spinal MNs. In addition, the postexercise behavior of QuadS responses was related to the duration of the contraction, pointing to a correlation between repeated activation of MNs and the subject's ability to maintain force. In conclusion, the study confirmed that an increased fraction of spinal MNs fire more than once in response to TMS when the muscle is fatigued. Repetitive MN firing may provide an adaptive mechanism to maintain motor unit activation and task performance during sustained voluntary activity.

Influence of CO2 on upper airway muscles and chest wall/diaphragm corticomotor responses assessed by transcranial magnetic stimulation in awake healthy subjects

2012 ◽  
Vol 112 (5) ◽  
pp. 798-805 ◽  
Author(s):  
Jean-Christian Borel ◽  
Cesar Augusto Melo-Silva ◽  
Simon Gakwaya ◽  
Frédéric Sériès
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Tidal Volume ◽  
Chest Wall ◽  
Healthy Subjects ◽  
Magnetic Stimulation ◽  
Minute Ventilation ◽  
Motor Evoked Potential ◽  
Upper Airway ◽  
Random Order ◽  
Respiratory Drive

Rationale: functional interaction between upper airway (UA) dilator muscles and the diaphragm is crucial in the maintenance of UA patency. This interaction could be altered by increasing respiratory drive. The aim of our study was to compare the effects of hypercapnic stimulation on diaphragm and genioglossus corticomotor responses to transcranial magnetic stimulation (TMS). Methods: 10 self-reported healthy men (32 ± 9 yr; body mass index = 24 ± 3 kg/m−2) breathed, in random order, room air or 5% and then 7% FiCO2, both balanced with pure O2. Assessments included ventilatory variables, isoflow UA resistance (at 300 ml/s), measurement of lower chest wall/diaphragm (LCW/diaphragm), and genioglossus motor threshold (MT) and motor-evoked potential (MEP) characteristics. TMS twitches were applied during early inspiration and end expiration at stimulation intensity 30% above LCW/diaphragm and genioglossus MT. Results: compared with room air, CO2 inhalation significantly augmented minute ventilation, maximal inspiratory flow, tidal volume, and tidal volume/respiratory time ratio. UA resistance was unchanged with CO2 inhalation. During 7% CO2 breathing, LCW/diaphragm MT decreased by 9.6 ± 10.1% whereas genioglossus MT increased by 7.2 ± 9%. CO2-induced ventilatory stimulation led to elevation of LCW/diaphragm MEP amplitudes during inspiration but not during expiration. LCW/diaphragm MEP latencies remained unaltered both during inspiration and expiration. Genioglossus MEP latencies and amplitudes were unchanged with CO2. Conclusion: in awake, healthy subjects, CO2-induced hyperventilation is associated with heightened LCW/diaphragm corticomotor activation without modulating genioglossus MEP responses. This imbalance may promote UA instability during increased respiratory drive.

scholarly journals Onset Latency of Motor Evoked Potentials in Motor Cortical Mapping with Neuronavigated Transcranial Magnetic Stimulation

2015 ◽  
Vol 9 (1) ◽  
pp. 62-69 ◽  
Author(s):  
Elisa Kallioniemi ◽  
Minna Pitkänen ◽  
Laura Säisänen ◽  
Petro Julkunen
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Motor Evoked Potentials ◽  
Motor Evoked Potential ◽  
Cortical Mapping ◽  
Abductor Pollicis Brevis ◽  
Motor Pathways ◽  
Motor Mapping ◽  
Cortical Motor ◽  
Abductor Digiti Minimi

Cortical motor mapping in pre-surgical applications can be performed using motor evoked potential (MEP) amplitudes evoked with neuronavigated transcranial magnetic stimulation. The MEP latency, which is a more stable parameter than the MEP amplitude, has not so far been utilized in motor mapping. The latency, however, may provide information about the stress in damaged motor pathways, e.g. compression by tumors, which cannot be observed from the MEP amplitudes. Thus, inclusion of this parameter could add valuable information to the presently used technique of MEP amplitude mapping. In this study, the functional cortical representations of first dorsal interosseous (FDI), abductor pollicis brevis (APB) and abductor digiti minimi (ADM) muscles were mapped in both hemispheres of ten healthy righthanded volunteers. The cortical muscle representations were evaluated by the area and centre of gravity (CoG) by using MEP amplitudes and latencies. As expected, the latency and amplitude CoGs were congruent and were located in the centre of the maps but in a few subjects, instead of a single centre, several loci with short latencies were observed. In conclusion, MEP latencies may be useful in distinguishing the cortical representation areas with the most direct pathways from those pathways with prolonged latencies. However, the potential of latency mapping to identify stressed motor tract connections at the subcortical level will need to be verified in future studies with patients.

Corticospinal output during muscular fatigue differs in multiple sclerosis patients compared to healthy controls

2012 ◽  
Vol 18 (10) ◽  
pp. 1500-1506 ◽  
Author(s):  
O Scheidegger ◽  
CP Kamm ◽  
SJ Humpert ◽  
KM Rösler
Keyword(s):  
Multiple Sclerosis ◽  
Healthy Subjects ◽  
Magnetic Stimulation ◽  
Group Differences ◽  
Healthy Controls ◽  
Stimulation Protocol ◽  
Contraction Force ◽  
Abductor Digiti Minimi ◽  
Fatiguing Exercise ◽  
Multiple Sclerosis Patients

Background: In multiple sclerosis (MS), fatigue is a common and often disabling symptom. It has multiple causes with central motor fatigue playing an important role. Objective: The objective of this study was to analyse the central motor conduction changes in relation to muscle contraction force during muscle fatigue and recovery in MS patients compared to healthy controls. Methods: A total of 23 MS patients with fatigue and 13 healthy subjects were assessed during 2 minutes of fatiguing exercise of the abductor digiti minimi muscle of the hand and the subsequent 7 minutes of recovery. Central motor conduction was quantified by transcranial magnetic stimulation using the triple stimulation protocol and calculating a central conduction index (CCI). Results: Force declined to 36% of the pre-exercise level (SD 16%; p < 0.01) in MS patients and to 44% (SD 9%, p < 0.01) in healthy subjects (group differences, not statistically significant). The decline of the CCI was significantly less marked in patients (–20%, SD 26%, p < 0.05) than in healthy subjects (–57%, SD 15%, p < 0.05; group differences, p < 0.05). The decline of force and CCI were not correlated in either group. Conclusions: During a fatiguing exercise, the decline in central motor conduction is significantly less pronounced in MS patients than healthy subjects, although the reduction of force is similar.

scholarly journals Motor disability in patients with multiple sclerosis: transcranial magnetic stimulation study

2020 ◽  
Vol 56 (1) ◽  
Author(s):  
Anssam Bassem Mohy ◽  
Aqeel Kareem Hatem ◽  
Hussein Ghani Kadoori ◽  
Farqad Bader Hamdan
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Lower Limb ◽  
Magnetic Stimulation ◽  
Motor Evoked Potential ◽  
Invasive Procedure ◽  
Single Pulse ◽  
Lower Limbs ◽  
Control Group ◽  
Conduction Time ◽  
Motor Disability

Abstract Background Transcranial magnetic stimulation (TMS) is a non-invasive procedure used in a small targeted region of the brain via electromagnetic induction and used diagnostically to measure the connection between the central nervous system (CNS) and skeletal muscle to evaluate the damage that occurs in MS. Objectives The study aims to investigate whether single-pulse TMS measures differ between patients with MS and healthy controls and to consider if these measures are associated with clinical disability. Patients and methods Single-pulse TMS was performed in 26 patients with MS who hand an Expanded Disability Status Scale (EDSS) score between 0 and 9.5 and in 26 normal subjects. Different TMS parameters from upper and lower limbs were investigated. Results TMS disclosed no difference in all MEP parameters between the right and left side of the upper and lower limbs in patients with MS and controls. In all patients, TMS parameters were different from the control group. Upper limb central motor conduction time (CMCT) was prolonged in MS patients with pyramidal signs. Upper and lower limb CMCT and CMCT-f wave (CMCT-f) were prolonged in patients with ataxia. Moreover, CMCT and CMCT-f were prolonged in MS patients with EDSS of 5–9.5 as compared to those with a score of 0–4.5. EDSS correlated with upper and lower limb cortical latency (CL), CMCT, and CMCT-f whereas motor evoked potential (MEP) amplitude not. Conclusion TMS yields objective data to evaluate clinical disability and its parameters correlated well with EDSS.

Improvement of hand dexterity following motor cortex rTMS in multiple sclerosis patients with cerebellar impairment

2008 ◽  
Vol 14 (7) ◽  
pp. 995-998 ◽  
Author(s):  
G Koch ◽  
S Rossi ◽  
C Prosperetti ◽  
C Codecà ◽  
F Monteleone ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Transcranial Magnetic Stimulation ◽  
Motor Cortex ◽  
Healthy Subjects ◽  
Magnetic Stimulation ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Hand Dexterity ◽  
Time Required ◽  
Multiple Sclerosis Patients ◽  
Cerebellar Symptoms

We tested the effects of 5-Hz repetitive transcranial magnetic stimulation (rTMS) over the motor cortex in multiple sclerosis (MS) subjects with cerebellar symptoms. rTMS improved hand dexterity in cerebellar patients ( n = 8) but not in healthy subjects ( n = 7), as detected by a significant transient reduction of the time required to complete the nine-hole pegboard task. rTMS of the motor cortex may be a useful approach to treat cerebellar impairment in MS patients.

Suppression of the transcallosal motor output: a transcranial magnetic stimulation study in healthy subjects

2004 ◽  
Vol 158 (2) ◽  
Author(s):  
Carlo Trompetto ◽  
Marco Bove ◽  
Lucio Marinelli ◽  
Laura Avanzino ◽  
Alessandro Buccolieri ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Healthy Subjects ◽  
Magnetic Stimulation ◽  
Motor Output
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