Faculty Opinions recommendation of A gradient in endogenous rhythmicity and oscillatory drive matches recruitment order in an axial motor pool.

2013 ◽  
Author(s):  
Joe Fetcho
Keyword(s):  
Endogenous Rhythmicity ◽  
Recruitment Order

Computer simulations of the effects of different synaptic input systems on motor unit recruitment

1993 ◽  
Vol 70 (5) ◽  
pp. 1827-1840 ◽  
Author(s):  
C. J. Heckman ◽  
M. D. Binder
Keyword(s):  
Motor Unit ◽  
Computer Simulations ◽  
Synaptic Input ◽  
Reciprocal Inhibition ◽  
Excitatory Input ◽  
Medial Gastrocnemius ◽  
Synaptic Inputs ◽  
Monte Carlo Techniques ◽  
Recruitment Order ◽  
Random Variance

1. The effects of four different synaptic input systems on the recruitment order within a mammalian motoneuron pool were investigated using computer simulations. The synaptic inputs and motor unit properties in the model were based as closely as possible on the available experimental data for the cat medial gastrocnemius pool and muscle. Monte Carlo techniques were employed to add random variance to the motor unit thresholds and forces and to sample the resulting recruitment orders. 2. The effects of the synaptic inputs on recruitment order depended on how they modified the range of recruitment thresholds established by differences in the intrinsic current thresholds of the motoneurons. Application of a uniform synaptic input to the pool (i.e., distributed equally to all motoneurons) resulted in a recruitment sequence that was quite stable even with the addition of large amounts of random variance. With 50% added random variance, the recruitment reversals did not exceed 8%. 3. The simulated monosynaptic input from homonymous Ia afferent fibers generated a twofold expansion of the range of recruitment thresholds beyond that attributed to the differences in the intrinsic current thresholds. The Ia input generated a small reduction in the number of recruitment reversals due to random variance (6% reversals at 50% random variance). The simulated monosynaptic vestibulospinal input generated a twofold compression of the range of recruitment thresholds that exerted a modest increase in the number of recruitment reversals (12% reversals at 50% random variance). 4. In comparison with the modest effects of the two monosynaptic inputs, the simulated oligosynpatic rubrospinal excitatory input exerted a nine-fold compression in the recruitment threshold range that resulted in a recruitment sequence that was highly sensitive to random variance. With 50% added random variance, the sequence became nearly random (40% reversals). 5. Reciprocal Ia inhibition was simulated by a uniform distribution within the pool, but its effects on recruitment order were highly dependent on the distribution of the excitatory input. Reciprocal inhibition exerted only minor effects on recruitment order when combined with the Ia or vestibulospinal inputs. However, when the excitatory drive was supplied by the rubrospinal input, even small amounts of reciprocal inhibition were sufficient to completely reverse the normal recruitment sequence. 6. The simulated monosynaptic Ia input was highly effective in compensating for the disruptive effects of rubrospinal excitation on recruitment order. Even a small Ia bias combined with the rubrospinal excitation was sufficient to halve the effects of random variance and to restore the normal recruitment sequence in the presence of rather large amounts of reciprocal inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)

The recruitment order of scapular muscles depends on the characteristics of the postural task

2016 ◽  
Vol 31 ◽  
pp. 40-47 ◽  
Author(s):  
Guillermo Mendez-Rebolledo ◽  
Valeska Gatica-Rojas ◽  
Eduardo Martinez-Valdes ◽  
H.B. Xie
Keyword(s):  
Recruitment Order ◽  
Postural Task

scholarly journals Recruitment Order Among Motoneurons From Different Motor Nuclei

1999 ◽  
Vol 81 (5) ◽  
pp. 2485-2492 ◽  
Author(s):  
Alan J. Sokoloff ◽  
Sondra G. Siegel ◽  
Timothy C. Cope
Keyword(s):  
Conduction Velocity ◽  
Biceps Femoris ◽  
Medial Gastrocnemius ◽  
Size Principle ◽  
Lateral Gastrocnemius ◽  
Decerebrate Cat ◽  
Ankle Muscles ◽  
Recruitment Order ◽  
Motor Nuclei ◽  
First Time

Recruitment order among motoneurons from different motor nuclei. The principles by which motoneurons (MNs) innervating different multiple muscles are organized into activity are not known. Here we test the hypothesis that coactivated MNs belonging to different muscles in the decerebrate cat are recruited in accordance with the size principle, i.e., that MNs with slow conduction velocity (CV) are recruited before MNs with higher CV. We studied MN recruitment in two muscle pairs, the lateral gastrocnemius (LG) and medial gastrocnemius (MG) muscles, and the MG and posterior biceps femoris (PBF) muscles because these pairs are coactivated reliably in stretch and cutaneous reflexes, respectively. For 29/34 MG-LG pairs of MNs, the MN with lower CV was recruited first either in all trials (548/548 trials for 22 pairs) or in most trials (225/246 trials for 7 pairs), whether the MG or the LG MN in a pair was recruited first. Intertrial variability in the force thresholds of MG and LG MNs recruited by stretch was relatively low (coefficient of variation = 18% on average). Finally, punctate stimulation of the skin over the heel recruited 4/4 pairs of MG-LG MNs in order by CV. By all of these measures, recruitment order is as consistent among MNs from these two ankle muscles as it is for MNs supplying the MG muscle alone. For MG-PBF pairings, the MN with lower CV was recruited first in the majority of trials for 13/24 pairs and in reverse order for 9/24 pairs. The recruitment sequence of coactive MNs supplying the MG and PBF muscles was, therefore, random with respect to axonal conduction velocity and not organized as predicted by the size principle. Taken together, these findings demonstrate for the first time, that the size principle can extend beyond the boundaries of a single muscle but does not coordinate all coactive muscles in a limb.

Recruitment order of motoneurons during functional tasks

1994 ◽  
Vol 79 (2) ◽  
Author(s):  
K.E. Jones ◽  
M. Lyons ◽  
P. Bawa ◽  
R.N. Lemon
Keyword(s):  
Recruitment Order

Recruitment Order of Cat Abducens Motoneurons and Internuclear Neurons

2003 ◽  
Vol 90 (4) ◽  
pp. 2240-2252 ◽  
Author(s):  
Ángel M. Pastor ◽  
David González-Forero
Keyword(s):  
Rectus Muscle ◽  
Neuronal Firing ◽  
Eye Position ◽  
High Dose ◽  
Recruitment Threshold ◽  
Ocular Reflex ◽  
Lateral Rectus Muscle ◽  
Vestibulo Ocular Reflex ◽  
Recruitment Order ◽  
Eye Velocity

Abducens neurons undergo a dose-dependent synaptic blockade (either disinhibition or complete blockade) when tetanus neurotoxin (TeNT) is injected into the lateral rectus muscle at either a low (0.5) or a high dose (5 ng/kg). We studied the firing pattern and recruitment order in abducens neurons both in control and after TeNT injection. The eye position threshold for recruitment of control abducens neurons was exponentially related to the eye position and velocity sensitivities. We also found a constancy of recruitment threshold for different eye movement modalities (spontaneous, optokinetic, and vestibular). Exponential relationships were found, as well, for eye velocity sensitivity during saccades and for position and velocity sensitivities during the vestibulo-ocular reflex. Likewise, inverse relationships were found between recruitment threshold or position sensitivity with the antidromic latency in control abducens neurons. These relationships, however, did not apply following TeNT treatment. Neuronal firing after TeNT appeared either disinhibited (low dose) or depressed (high dose), but the relationships between neuronal sensitivities and recruitment still applied. However, the pattern of recruitment shifted toward the treated side as more inputs were blocked by the low- and high-dose treatments, respectively. Nonetheless, although the recruitment-to-sensitivity relationships persisted under the TeNT synaptic blockade, we conclude that synaptic inputs are determinant for establishing the recruitment threshold and recruitment spacing of abducens motoneurons and internuclear neurons.

Motor unit anatomy and physiology

2017 ◽  
Author(s):  
Matthew Pitt
Keyword(s):  
Quantitative Analysis ◽  
Motor Unit ◽  
Interference Pattern ◽  
Theoretical Explanation ◽  
Motor Unit Potential ◽  
Amplitude Analysis ◽  
Anatomy And Physiology ◽  
Needle Electromyography ◽  
Accurate Quantitative Analysis ◽  
Recruitment Order

This chapter focuses on the signals recorded with needle electromyography (EMG) and the measurement of their specific parameters. These parameters include duration, amplitude, number of phases, and stability. The concept of the electrophysiologic biopsy and the explanation of unusual findings seen on EMG are introduced. In relation to the interference pattern, discussions of the firing rate, recruitment order, and interference pattern are given. Moving from the theoretical explanation of the findings, the problems of the accurate quantitative analysis of the motor unit potential are discussed and measures to improve quantification, particularly in children, are highlighted. The importance of filter settings, the storage of signals, and the different ways of collecting and analysing the potentials are all covered. This section finishes with discussion of the normative range for motor unit duration, and concludes with the automatic analysis of the interference pattern, including turns/amplitude analysis, number of short segments measurement, and envelope analysis.

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