Electromechanical coupling and synchronous firing of single wrist extensor motor units in sporadic amyotrophic lateral sclerosis

Schmied, Annie; Pouget, Jean; Vedel, Jean‐Pierre

doi:10.1016/s1388-2457(99)00032-2

Cited by 55 publications

(49 citation statements)

References 49 publications

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“…The lack of intergroup difference in the electromechanomyographical and electromechanical ratios is in contrast to findings by Barry et al, 2 Marusiak et al, 20,21 Orizio et al, 25 and Schmied et al 28 Barry et al and Orizio et al found smaller values for the RMS-MMG/EMG ratio in patients with neuromuscular disorders (Becker muscular dystrophy, Duchenne muscular dystrophy, myotonic muscular dystrophy, congenital myopathy, mild myopathy, and dermatomyositis) compared with control subjects. They explained their results as an effect of FT muscle fiber atrophy and replacement of the fibers with connective tissue, which is stiffer.…”

Section: Discussioncontrasting

confidence: 67%

Electromyography and mechanomyography of elbow agonists and antagonists in Parkinson disease

et al. 2009

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The purpose of this study was to assess the electromyographic (EMG) and mechanomyographic (MMG) activities of agonist and antagonist muscles in Parkinson disease patients during maximal isometric elbow contraction in flexion and extension. Ten elderly females with Parkinson disease (average age 75 years) and 10 age-matched healthy females were tested. The torque and the EMG and MMG signals from biceps brachii and triceps brachii were recorded during sustained maximal voluntary isometric contraction of the elbow flexors and extensors. There were no intergroup differences in the EMG and MMG activities of agonist and antagonist muscles or in torque. This might be because the Parkinson subjects were tested during their medication "ON" phase, or perhaps maximal isometric contraction (MVC) induced greater active muscle stiffness that affected the MMG signal. Muscle Nerve 40: 240-248, 2009.

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Section: Discussioncontrasting

confidence: 67%

Electromyography and mechanomyography of elbow agonists and antagonists in Parkinson disease

et al. 2009

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“…For example, motor unit synchronization is lower during index finger flexion compared with abduction (Bremner et al 1991), but is greater during lengthening compared with shortening muscle contractions . These findings are interpreted as a change in the number and/or excitability of branched corticospinal inputs used to perform these tasks (Farmer et al 1990;Schmied et al 1999). However, most measurements of the strength of motor unit synchronization in humans are performed in hand or wrist muscles, which have strong corticospinal projections to motor neurons (Clough et al 1968;Phillips and Porter 1964).…”

Section: Motor Unit Synchronizationmentioning

confidence: 99%

“…For voluntary isometric contractions of fresh muscle, the prevailing view is that motor unit synchronization arises from common synaptic input received by motor neurons from either branched last-order interneurons or cortical efferents that receive common input (Datta et al 1991;Farmer et al 1990Farmer et al , 1993bMantel and Lemon 1987;Moritz et al 2005;Schmied et al 1999), but does not seem to be influenced by peripheral afferents (Farmer et al 1993a(Farmer et al , 1997. However, the mechanisms responsible for an increase in motor unit synchronization after eccentric exercise are less clear, because the exerciseinduced muscle damage is likely to cause physiological adjustments within the muscle that influence both the spinal and cortical control of movement.…”

Section: Motor Unit Synchronizationmentioning

confidence: 99%

“…In human limb muscles, for example, changes in motor unit synchronization during isometric contractions have been observed when forces are exerted in different directions (Bremner et al 1991), during performance of an action that requires significant attention (Schmied et al 1999), and when object compliance has been altered (Kilner et al 2002). Furthermore, correlated motor unit activity can be altered during changes in muscle length, because motor unit synchronization is enhanced during slowlengthening contractions and low-frequency (2-12 Hz) coherence is reduced during shortening contractions .…”

Section: Introductionmentioning

confidence: 99%

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Motor Unit Synchronization Is Increased in Biceps Brachii After Exercise-Induced Damage to Elbow Flexor Muscles

Dartnall¹,

Nordstrom²,

Semmler³

2008

Journal of Neurophysiology

104

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“…However, some of the few single motor unit studies performed in patients with ALS have not been covered in this review. The interested reader may find additional information in Schmied et al (1999), Attarian et al (2006Attarian et al ( , 2008.…”

mentioning

confidence: 99%

Mechanisms underlying firing in healthy and sick human motoneurons

2015

Frontiers Research Topics

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Keywords: human motoneuron discharge mechanisms, motor unit, afterhyperpolarization and delayed depolarization, double and triple discharges, recruitment and rate coding, axon and peripheral afferents, excitability, motoneuron pathologyIn an address to the British Association for the Advancement of Science in Cambridge, Professor Sherrington introduced the terms "motor neurone" and "the final common path," the latter term implying that all motor commands converge onto the motoneuron which integrates the incoming information and passes the net information to the muscle for contraction (Sherrington, 1904). The relative ease of access of the spinal motoneuron made it feasible to set up techniques for investigating the physiological, biophysical and molecular properties of these neurons. It became the most investigated neuron of the CNS in the twentieth century and the information gained from studies on motoneurons formed the basis for examining the other neurons of the CNS. Since the compound action potential of a muscle unit is strictly related one-to-one to the action potential arriving from the innervating motoneuron, the statistical analysis of muscle unit action potentials provides an investigator with an elegant way to probe the properties of motoneurons in behaving humans. In the following review the terms motoneuron and motor unit might be used interchangeably. Different aspects of human motoneuron investigations in health and disease are presented in 16 articles of this topic which are summarized below.An increase in the net excitatory synaptic input to the motoneuron pool results in an increase in the level of muscle contraction by recruitment of additional motor units (MUs) and an increase in firing rates of the already recruited units (Milner-Brown et al., 1973;Henneman et al., 1974). The principle of orderly recruitment of motoneurons by size was originally proposed by Henneman (1957) but was later questioned by other researchers presenting examples of selective, rather than orderly recruitment (e.g., Smith et al., 1980). These controversies are assessed by Bawa et al. (2014), and the opinion unifying the concept of orderly recruitment is presented. In humans, increases in firing rates of motor units have been shown to follow the "onion skin" pattern at lower levels of contraction, meaning that the lower-threshold motor units discharge with higher rates than higher-threshold ones. However, studies performed on the whole range of muscle forces indicated that for higher force levels the motor unit firing rate follows a "reverse onion skin" pattern. Hu et al. (2014) decided to approach this problem using small surface electrodes and step increases in force instead of the "ramp and hold" protocols used by previous authors. They showed that the "onion skin" pattern was preserved until 15% of maximal voluntary contraction, and from their results predict this pattern to be valid for the whole range of muscle forces, which is not supported by the previous published works. However, the reported rate saturation ...

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Electromechanical coupling and synchronous firing of single wrist extensor motor units in sporadic amyotrophic lateral sclerosis

Cited by 55 publications

References 49 publications

Electromyography and mechanomyography of elbow agonists and antagonists in Parkinson disease

Electromyography and mechanomyography of elbow agonists and antagonists in Parkinson disease

Motor Unit Synchronization Is Increased in Biceps Brachii After Exercise-Induced Damage to Elbow Flexor Muscles

Mechanisms underlying firing in healthy and sick human motoneurons

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