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Coordinated alpha and gamma control of muscles and spindles in movement and posture
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2015 (English)In: Frontiers in Computational Neuroscience, ISSN 1662-5188, E-ISSN 1662-5188, Vol. 9, 122Article in journal (Refereed) Published
Abstract [en]

Mounting evidence suggests that both a and gamma motoneurons are active during movement and posture, but how does the central motor system coordinate the alpha-gamma controls in these tasks remains sketchy due to lack of in vivo data. Here a computational model of alpha-gamma control of muscles and spindles was used to investigate a -gamma integration and coordination for movement and posture. The model comprised physiologically realistic spinal circuitry, muscles, proprioceptors, and skeletal biomechanics. In the model, we divided the cortical descending commands into static and dynamic sets, where static commands (alpha(s) and gamma(s)) were for posture maintenance and dynamic commands (alpha(d) and gamma(d)) were responsible for movement. We matched our model to human reaching movement data by straightforward adjustments of descending commands derived from either minimal-jerk trajectories or human EMGs. The matched movement showed smooth reach-to-hold trajectories qualitatively close to human behaviors, and the reproduced EMGs showed the classic tri-phasic patterns. In particular, the function of gamma(d) was to gate the alpha(d) command at the propriospinal neurons (PN) such that antagonistic muscles can accelerate or decelerate the limb with proper timing. Independent control of joint position and stiffness could be achieved by adjusting static commands. Deefferentation in the model indicated that accurate static commands of as and gamma(s) are essential to achieve stable terminal posture precisely, and that the gamma(d) command is as important as the alpha(d) command in controlling antagonistic muscles for desired movements. Deafferentation in the model showed that losing proprioceptive afferents mainly affected the terminal position of movement, similar to the abnormal behaviors observed in human and animals. Our results illustrated that tuning the simple forms of alpha-gamma commands can reproduce a range of human reach-to-hold movements, and it is necessary to coordinate the set of alpha-gamma descending commands for accurate and stable control of movement and posture.

Place, publisher, year, edition, pages
[Li, Si; Zhuang, Cheng; Hao, Manzhao; He, Xin; Marquez, Juan C.; Lan, Ning] Shanghai Jiao Tong Univ, Med X Res Inst, Sch Biomed Engn, Shanghai 200030, Peoples R China. [Marquez, Juan C.] Royal Inst Technol, Sch Technol & Hlth, Stockholm, Sweden. [Niu, Chuanxin M.] Shanghai Jiao Tong Univ, Sch Med, Ruijin Hosp, Dept Rehabil, Shanghai 200030, Peoples R China. [Lan, Ning] Univ So Calif, Div Biokinesiol & Phys Therapy, Los Angeles, CA USA., 2015. Vol. 9, 122
Keyword [en]
alpha-gamma motor system, propriospinal neurons, spinal circuits, muscle and spindle, computational modeling, simulation, movement and posture
National Category
Bioinformatics (Computational Biology) Neurosciences
URN: urn:nbn:se:kth:diva-176338DOI: 10.3389/fncom.2015.00122ISI: 000362660100001ScopusID: 2-s2.0-84944327537OAI: diva2:868020

QC 20151109

Available from: 2015-11-09 Created: 2015-11-03 Last updated: 2015-11-09Bibliographically approved

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