Motor unit recruitment strategies and muscle properties determine the influence of synaptic noise on force steadiness

被引:131
作者
Dideriksen, Jakob L. [3 ]
Negro, Francesco
Enoka, Roger M. [2 ]
Farina, Dario [1 ]
机构
[1] Univ Gottingen, Univ Med Ctr Gottingen, Bernstein Ctr Computat Neurosci, Dept Neurorehabil Engn, D-37075 Gottingen, Germany
[2] Univ Colorado, Dept Integrat Physiol, Boulder, CO 80309 USA
[3] Aalborg Univ, Dept Hlth Sci & Technol, Ctr Sensory Motor Interact SMI, Aalborg, Denmark
基金
欧洲研究理事会;
关键词
motor control; neuromuscular modeling; SLOW LENGTHENING CONTRACTIONS; DORSAL INTEROSSEOUS MUSCLE; SHORT-TERM SYNCHRONIZATION; RATE CODING ORGANIZATION; SIGNAL-DEPENDENT NOISE; ELBOW FLEXOR MUSCLES; ISOMETRIC CONTRACTIONS; HAND MUSCLE; OLD ADULTS; SUBMAXIMAL CONTRACTIONS;
D O I
10.1152/jn.00938.2011
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
Dideriksen JL, Negro F, Enoka RM, Farina D. Motor unit recruitment strategies and muscle properties determine the influence of synaptic noise on force steadiness. J Neurophysiol 107: 3357-3369, 2012. First published March 14, 2012; doi:10.1152/jn.00938.2011.-Motoneurons receive synaptic inputs from tens of thousands of connections that cause membrane potential to fluctuate continuously (synaptic noise), which introduces variability in discharge times of action potentials. We hypothesized that the influence of synaptic noise on force steadiness during voluntary contractions is limited to low muscle forces. The hypothesis was examined with an analytical description of transduction of motor unit spike trains into muscle force, a computational model of motor unit recruitment and rate coding, and experimental analysis of interspike interval variability during steady contractions with the abductor digiti minimi muscle. Simulations varied contraction force, level of synaptic noise, size of motor unit population, recruitment range, twitch contraction times, and level of motor unit short-term synchronization. Consistent with the analytical derivations, simulations and experimental data showed that force variability at target forces above a threshold was primarily due to low-frequency oscillations in neural drive, whereas the influence of synaptic noise was almost completely attenuated by two low-pass filters, one related to convolution of motoneuron spike trains with motor unit twitches (temporal summation) and the other attributable to summation of single motor unit forces (spatial summation). The threshold force above which synaptic noise ceased to influence force steadiness depended on recruitment range, size of motor unit population, and muscle contractile properties. This threshold was low (<10% of maximal force) for typical values of these parameters. Results indicate that motor unit recruitment and muscle properties of a typical muscle are tuned to limit the influence of synaptic noise on force steadiness to low forces and that the inability to produce a constant force during stronger contractions is mainly attributable to the common low-frequency oscillations in motoneuron discharge rates.
引用
收藏
页码:3357 / 3369
页数:13
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