Motor activity following the silent period in human muscle

Alston, Walter; Angel, Ronald W.; Fink, F. S.; Hofmann, William W.

doi:10.1113/jphysiol.1967.sp008201

Cited by 28 publications

(8 citation statements)

References 14 publications

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“…10. Similar responses to sudden unloading have been described by Angel, Eppler & lannone (1965), Alston, Angel, Fink & Hofmann (1967) and earlier writers, in muscles initially maintaining a steady force at constant length. In their experiments silence did not persist during free shortening, but was terminated by a large burst of activity after about a tenth of a second, part of the original Entlastungsreflex of Hansen & Hoffmann (1922).…”

Section: C D Marsden P a Merton And H B Mortonsupporting

confidence: 82%

Servo action in the human thumb.

Marsden¹,

Merton²,

Morton³

1976

The Journal of Physiology

305

184

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SUMMARY1. The servo-like properties of muscle in healthy human subjects have been studied by interfering unexpectedly with flexion movements of the top joint of the thumb. This movement is carried out by the flexor pollicis longus muscle only.2. The movements were standardized in rate by giving the subject a tracking task. They started off against a constant torque load offered by an electric motor. 3. In some movements the load remained constant, but in others, in mid-course, perturbations were introduced at random. Either the movement was halted, or released and allowed to accelerate by reducing the load, or reversed by suddenly increasing the current in the motor, so stretching the muscle. 4. Usually eight or sixteen responses to each kind of perturbation and a similar number of controls against a constant load were averaged. 5. Muscle activity was recorded as the electromyogram from surface electrodes over the belly of the long flexor in the lower forearm. Action potentials were usually full-wave rectified and integrated.6. About 50 msec after a perturbation the muscle's activity alters in such a sense as to tend to compensate for the perturbation, i.e. it increases after a halt or a stretch and decreases after a release. The latency is similar in each case.7. These responses are interpreted as manifestations of automatic servo action based on the stretch reflex. They are considered to be too early to be voluntary.8. This interpretation was supported by measuring voluntary reaction times to perturbations under tracking conditions. They were found to be 90 msec or longer.9. When the initial load was increased by a factor of 10, the servo

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Section: C D Marsden P a Merton And H B Mortonsupporting

confidence: 82%

Servo action in the human thumb.

Marsden¹,

Merton²,

Morton³

1976

The Journal of Physiology

305

184

View full text Add to dashboard Cite

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“…The silent period after cortical stimulation can be generated by several mechanisms [4], [5]. One possible explanation for the silent period is the results of activation of inhibitory neurones projecting onto the pyramidal cells of the motor cortex.…”

Section: Discussionmentioning

confidence: 99%

Suppression of Electromyogram of Hand Muscle Elicited by Transcranial Magnetic Stimulation Over the Primary Motor Cortex

et al. 2008

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Cortical motor neuronal activation by transcranial magnetic stimulation (TMS) over the primary motor cortex area (M1) produces efferent signals that pass through the cortico-spinal tracts. As a result, motor evoked potentials (MEPs) are observed at muscles innervated by the stimulated motor neurons. It is well known that TMS can cause a silent period in the voluntary electromyogram (EMG). In the present study, TMS was applied to the M1 during thumb tapping. The influence of TMS on voluntary muscle contraction was discussed. Thumb trajectory was observed with a three-dimensional tracking device, and EMG of the abductor pollicis brevis (APB) muscle was also measured. The authors confirmed a change in thumb velocity in the downward direction during voluntary movement when TMS was applied, indicating that tissue excitation elicited by TMS causes loss of control of peripheral muscle motor control during voluntary movement.

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“…The silent period can therefore be taken as a crude index of spindle sensitivity [5][6][7][17][18][19][20]. A cyclic appearance of the silent period and the return of the motor activity of the muscle with sudden retention of movement in one evoked reflex is related to the mechanism of intramuscular rhythmic oscillation and the grouping of many active tonic motoneurons in the paraspinal muscles [1,8,[14][15][16].…”

Section: Discussionmentioning

confidence: 99%

“…The pause in discharge can be observed only when a certain threshold value of acceleration and shortening of the muscle is exceeded, and it occurs with constant latency corresponding to that of the proprioceptive reflex [9,18,20]. The rebound after the silent period in the unloading refelx results from activation of a pool of motoneurons, all of which reach the firing threshold sinmltaneously after previous silence [1,3,4,20].…”

Section: Introductionmentioning

confidence: 99%

Neurophysiological mechanism of the unloading reflex as a prognostic factor in the early stages of idiopathic adolescent scoliosis

Dobosiewicz¹

1997

Eur Spine J

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This paper presents a new neurophysiological method of evaluating the risk of progression in idiopathic scoliosis in the early stages of the disease, by investigating the unloading reflex in paraspinal muscles. The study included 394 patients with scoliosis and 70 healthy children. Latency of the unloading reflex and repeatability of the rebound and silent period were analysed for each reflex evoked. Prolonged latency and minimal number of cycles are the most important factors in the evaluation of progressive idiopathic scoliosis. The method can be used to detect progressive idiopathic scoliosis in the early stages of the disease. The high sensitivity of the method means it can be used as a basis on which to take an early decision to perform surgery.

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Motor activity following the silent period in human muscle

Cited by 28 publications

References 14 publications

Servo action in the human thumb.

Servo action in the human thumb.

Suppression of Electromyogram of Hand Muscle Elicited by Transcranial Magnetic Stimulation Over the Primary Motor Cortex

Neurophysiological mechanism of the unloading reflex as a prognostic factor in the early stages of idiopathic adolescent scoliosis

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