Transcranial Magnetic Stimulation with the Maximum Voluntary Muscle Contraction Facilitates Motor Neuron Excitability and Muscle Force (original) (raw)
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Muscle & Nerve, 1996
~ ~ Vertex transcranial magnetic stimulation (TMS) elicited tibialis anterior motor evoked potentials (MEPs) and silent periods (SPs) that were recorded during and following isometric maximal volitional contraction (MVC). During MVC in 6 healthy subjects, MEP amplitudes in the exercised muscle showed an increasing trend from an initial value of 4539 t 809 pV (mean -c SE) to 550 -c 908 pV ( P < 0.13) while force and EMG decreased ( P < 0.01). Also, SP duration increased from 165 2 37 ms to 231 5 32 ms (P < 0.01). Thus, during a fatiguing MVC both excitatory and inhibitory TMS-induced responses increased. TMS delivered during repeated brief 10% MVC contractions before and after a fatiguing MVC in 5 subjects, showed no change in MEP amplitude but SP duration was prolonged after MVC. This SP prolongation was focal to the exercised muscle. Silent periods recorded after pyramidal tract stimulation were unchanged following the MVC. These results suggest that MEP and SP might have common sources of facilitation during an MVC and that inhibitory mechanisms remain focally augmented following a fatiguing MVC. o 1996 John Wiley & Sons, Inc.
Clinical Neurophysiology, 2002
Objectives: The objective of the present study is to quantify the effects of voluntary muscle contraction of the small hand (abductor pollicis brevis, first dorsal interosseus (FDI)) and forearm muscles (extensor carpi radialis (ECR), extensor carpi ulnaris (ECU), flexor carpi radialis (FCR) and flexor carpi ulnaris (FCU)) on motor evoked potentials (MEPs). Methods: MEPs were recorded in 12 healthy subjects by a circular coil placed over the vertex at 1.2 times the resting motor threshold at different levels of the muscle contraction (0-100% of maximum voluntary contraction (MVC)). The effects of transcranial magnetic stimulation (TMS) on the onset latency, MEP area and silent period (SP) as a function of the %MVC were evaluated using a piecewise linear regression analysis. Results: The MEP areas for the small hand muscles were almost completely saturated at 20% of MVC. In contrast, the MEP areas for radial muscles (ECR, FCR) had a dual increase at 40% of MVC while the ulnar muscles (ECU, FCU) had a dual increase at 20% of MVC. A uniform latency shift (1.5-3 ms reduction) was observed in all muscles with a changing point at 10% of MVC. The SPs were the longest for FDI and were not significantly influenced by MVC for any muscles. Conclusions: The excitatory and inhibitory effects of TMS on the MEPs differed for the small hand and forearm muscles and also between the ulnar and radial muscles. These results probably resulted from the different degrees of direct corticomotoneuronal inputs to each muscle and the inherent properties of the spinal motoneurons.
Muscle vibration: Different effects on transcranial magnetic and electrical stimulation
Muscle & Nerve, 1999
Transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (TES) were applied before and 3 s after onset of vibration (0.5 mm, 80 Hz) of the right extensor carpi radialis muscle in 5 healthy subjects. Vibration induced significant augmentation and latency shortening of motor evoked potentials elicited by TMS, but not TES. This provides evidence for an involvement of cortical mechanisms by muscle vibration in the augmentation of MEPs following TMS.
Facilitation of muscle responses to magnetic brain stimulation by mechanical stimuli in man
Experimental Brain Research, 1988
Transcranial magnetic brain stimuh were applied to 9 normal subjects and compound muscle action potentials were recorded from the right abductor digiti minimi with surface electrodes. Vibration of 120 Hz, 0.6 mm peak to peak amplitude, applied to the muscle tendon enhanced its responses to magnetic brain stimuli. This facilitation corresponds to the tonic vibration reflex. Inhibition of muscle responses was not seen with vibration. Thus it is likely that the known inhibition of stretch reflexes by vibration is purely presynaptic. Small rectangular mechanical stimuli (rise time 200 ram/s, amplitude I ram) applied to ADM elicited short and long loop reflex responses. When brain stimuli were given 7-16 ms after the muscle tap, muscle responses were enhanced. It is argued that this is a result of the summation of the effects of Ia afferent impulses and descending pyramidal volleys at the alpha motoneurones. A separate late facilitation corresponding with the arrival of muscle afferent inputs to the sensori-motor cortex was not seen.
International Congress Series, 2004
In healthy subjects, we studied the late electromyographic response elicited by transcranial magnetic stimulation (TMS) applied at the level of the foramen magnum in the left soleus muscle in an upright and supine posture. The late response at the latency of approximately 40 ms was constantly elicited during both postures. It was elicited during planter flexion, but not dorsi flexion. Additionally, no response appeared in the relaxed muscle. Those behaviours are the same as that of the long-loop reflex (LLR). We believe that the late response may be a long-loop reflex. D 2004 Elsevier B.V. All rights reserved.
Repeatability and reliability of muscle relaxation properties induced by motor cortical stimulation
Journal of Applied Physiology, 2018
Impaired muscle relaxation is a feature of many neuromuscular disorders. However, few tests are available to quantify muscle relaxation. Transcranial magnetic stimulation (TMS) of the motor cortex can induce muscle relaxation by abruptly inhibiting corticospinal drive. The aim of our study was to investigate whether repeatability and reliability of TMS-induced relaxation are greater than voluntary relaxation. Furthermore, effects of sex, cooling, and fatigue on muscle relaxation properties were studied. Muscle relaxation of deep finger flexors was assessed in 25 healthy subjects (14 men and 11 women, age 39.1 Ϯ 12.7 and 45.3 Ϯ 8.7 yr, respectively) with handgrip dynamometry. All outcome measures showed greater repeatability and reliability in TMS-induced relaxation compared with voluntary relaxation. The within-subject coefficient of variability of normalized peak relaxation rate was lower in TMS-induced relaxation than in voluntary relaxation (3.0% vs. 19.7% in men and 6.1% vs. 14.3% in women). The repeatability coefficient was lower (1.3 vs. 6.1 s Ϫ1 in men and 2.3 vs. 3.1 s Ϫ1 in women) and the intraclass correlation coefficient was higher (0.95 vs. 0.53 in men and 0.78 vs. 0.69 in women) for TMS-induced relaxation compared with voluntary relaxation. TMS enabled demonstration of slowing effects of sex, muscle cooling, and muscle fatigue on relaxation properties that voluntary relaxation could not. In conclusion, repeatability and reliability of TMS-induced muscle relaxation were greater compared with voluntary muscle relaxation. TMS-induced muscle relaxation has the potential to be used in clinical practice for diagnostic purposes and therapy effect monitoring in patients with impaired muscle relaxation. NEW & NOTEWORTHY Transcranial magnetic stimulation (TMS)-induced muscle relaxation demonstrates greater repeatability and reliability compared with voluntary relaxation, represented by the ability to demonstrate typical effects of sex, cooling, and fatigue on muscle relaxation properties that were not seen in voluntary relaxation. In clinical practice, TMS-induced muscle relaxation could be used for diagnostic purposes and therapy effect monitoring. Furthermore, fewer subjects will be needed for future studies when using TMS to demonstrate differences in muscle relaxation properties.
Experimental Brain Research, 2006
The purpose of this research was to determine whether motor cortex excitability assessed using transcranial magnetic stimulation (TMS) is less variable when subjects maintain a visually controlled low-level contraction of the muscle of interest. We also examined the dependence of single motor evoked potential (MEP) amplitude on stimulation intensity and pre-stimulus muscle activation level using linear and non-linear multiple regression analysis. Eight healthy adult subjects received single pulse TMS over the left motor cortex at a point where minimal stimulation intensity was required to produce MEPs in extensor digitorum communis (EDC). Voluntary activation of the muscle was controlled by visual display of a target force (indicated by a stable line on an oscilloscope) and the isometric force produced as the subject attempted to extend the fingers (indicated by a line on the oscilloscope representing the finger extension force) while subjects were instructed to: exert zero extension force (0%) and produce forces equal to 5 and 10% of maximum voluntary finger extension under separate conditions. Relative variability (coefficient of variation) of single MEPs at a constant stimulus intensity and of pre-stimulus muscle EMG was lower during maintained 5 and 10% contractions than at 0% contraction levels. Therefore, maintaining a stable low intensity contraction helps stabilize cortical and spinal excitability. Multiple regression analyses showed that a linear dependence of single MEPs on stimulation intensity and pre-stimulus muscle activation level produced similar fits to those for a non-linear dependence on stimulus intensity and a linear dependence on pre-stimulus EMG. Thus, a simple linear method can be used to assess dependence of single MEP amplitudes on both stimulus intensity (to characterize slope of the recruitment curve) and low intensity background muscle activation level.
Electroencephalography and clinical neurophysiology, 1995
We examined the inhibitory effect of a brief train of digital (D2) electrical stimuli at 4 times perception threshold on transcranial magnetic motor evoked potentials (MEPs) recorded from abductor pollicis brevis (APB) and flexor carpi radialis (FCR) muscles ipsilateral to the side of D2 stimulation. We compared this to the inhibitory effect of ipsilateral D2 stimulation on averaged rectified EMG recorded at 10% maximum voluntary contraction and on F-responses and H-reflexes recorded from these same muscles. We also compared MEPs recorded following D2 stimulation just above perception threshold to MEPs following higher intensity D2 stimulation. As well, we assessed the effect of preceding D2 stimulation on MEPs recorded from a relaxed versus tonically contracted hand muscle. D2 stimulation elicited a triphasic response of modest MEP facilitation followed by inhibition and further facilitation. The duration and onset of MEP inhibition correlated with those of the initial period of re...
Neuroscience Letters, 1986
Magnetic brain stimulation-Compound muscle action potential-Facilitation-Human An intense rapidly changing magnetic field generated in a coil over the scalp can excite motor pathways to hand muscles. With a suprathreshold stimulus, the amplitude of the muscle action potential of the abductor digiti minimi is increased: by weak contraction of the muscle itself, by weak contraction of the ipsilateral first dorsal interosseus, by stronger contraction of the contralateral abductor digiti minimi, but not by contraction of the contralateral first dorsal interosseus, nor by the ipsilateral quadriceps muscle. This facilitation of response to brain stimulation may occur by two mechanisms, one related to the focussing of attention onto a particular hand, the second involving a rise in excitability of homologous motor pathways.
Surabaya Physical Medicine and Rehabilitation Journal
Background: Stroke may disrupt a patient’s motor function, consequently affecting the quality of life. A stroke surviving brain has the ability to repair itself through neuroplasticity mechanism. Transcranial Magnetic Stimulation (TMS) is a non-invasive device which can be used to stimulate the lesioned part of the brain in hope of triggering neuroplasticity.Aims: To find prove of the repetitive Transcranial Magnetic Stimulation (rTMS) effect on extensor digitorum communis muscle strength improvement in ischemic stroke patients.Methods: Subjects suitable with the inclusion criteria (N=18) were divided into two groups, control group and intervention group. The control group underwent conventional therapy exclusively every day for 5 days in a row, while the intervention group underwent rTMS therapy and conventional therapy every day for 5 days in a row. Extensor digitorum communis muscle strength was measured using surface electromyography (sEMG) before and after treatment.Result: Si...