A model of closed-loop motor unit including muscle spindle feedback (Kim, 2020)

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Persistent inward current generating ion channels are located over spinal motoneurons and actively recruited during normal behaviors. Constructing a realistic computational model of closed-loop motor unit, a motoneuron and muscle fibers that it innervates including muscle spindle afferents, the study reveals functional linkage between persistent inward current location, motoneuron discharge pattern and muscle force output at various muscle lengths. This systematic analysis may provide useful insights into interplay of spinal and muscular mechanisms in control of movements.
1 . Kim H (2020) Linking Motoneuron PIC Location to Motor Function in Closed-Loop Motor Unit System Including Afferent Feedback: A Computational Investigation. eNeuro [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Neuron or other electrically excitable cell;
Brain Region(s)/Organism: Spinal motoneuron;
Cell Type(s):
Channel(s): I Calcium; I Potassium; I Sodium; I_AHP;
Gap Junctions:
Gene(s): Cav1.3 CACNA1D;
Simulation Environment: NEURON;
Model Concept(s): Motor control;
Implementer(s): Kim, Hojeong [hojeong.kim03 at gmail.com];
Search NeuronDB for information about:  I Sodium; I Calcium; I Potassium; I_AHP;
The simulation data used for the present study can be reproduced via the following steps. 

STEP 1: Set the value of "dpath" and "gcalbar" for the localization of Cav1.3 channels and their peak conductance over the motoneuron in the hoc file (add_pics_istim.hoc or add_pics_syns.hoc).

STEP 2: Set the value of "gmax_IaSyn" for the localization of muscle spindle inputs and thier peak conductance over the motoneuron in the hoc file (group_Ia.hoc).

STEP 3: Run the main hoc file (motor_unit.hoc).

STEP 4: Set the value of "amp" for the state of muscle length on the Xm[0] GUI window.

STEP 5: Push the "Init & Run" botton on the RunControl GUI window for starting simulation.

The STEP 1-5 should be repeated for simulations at different conditions of "dpath" and "xm". The defualt values of "dpath" and "xm" were set to 600 microns and -8 mm for Figs 2-7 and 800 microns and -16 mm for Figs 8. For Fig 9, the defualt value of "dpath" was set to 800 microns and the value of "Gaff" varied from 0 to 19 uS/cm^2 in a sinusoidal form. The simulation codes were compiled for use in the Microsoft Windows operating system (version > 7 and 64 bit).

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