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

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Accession:266732
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.
Reference:
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:
Receptor(s):
Gene(s): Cav1.3 CACNA1D;
Transmitter(s):
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;
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Kim2020
fig9
Ca_conc.mod *
CaL.mod *
CaN.mod *
KCa.mod *
KDr.mod *
module1_2.mod *
module3.mod *
mStepIClamp.mod
Naf.mod *
Nap.mod *
syn_Ia_sinewave.mod
Xm.mod *
add_hil_is.hoc *
add_muscle_unit.hoc *
add_pics_istim.hoc
Ca_conc.o *
CaL.o *
CaN.o *
fig.ses
fixnseg.hoc *
group_Ia_sinewave.hoc
KCa.o *
KDr.o *
mem_mechanism_acti.hoc *
mem_mechanism_muscle.hoc *
mem_mechanism_pass.hoc *
mod_func.c
mod_func.o
module1_2.o *
module3.o *
motor_unit.hoc
mStepIClamp.o
Naf.o *
Nap.o *
nrnmech.dll
syn_Ia_sinewave.o
v_e_moto6_export.hoc *
Xm.hoc *
Xm.o *
                            
    COMMENT
    This mechanism is a point process for generation of multiple step currents at different amplitudes over time.
	Since this is an electrode current, positive values of i depolarize the cell
    and in the presence of the extracellular mechanism there will be a change
    in vext since i is not a transmembrane current but a current injected
    directly to the inside of the cell.
    ENDCOMMENT

    NEURON {
        POINT_PROCESS mStepIClamp
        RANGE del, dur
		RANGE ip1, ip2, ip3, ip4, ip5
		RANGE pon1, pon2, pon3, pon4, pon5
		RANGE poff1, poff2, poff3, poff4, poff5
		RANGE i0, s
        ELECTRODE_CURRENT i
    }

    UNITS {
        (nA) = (nanoamp)
    }

    PARAMETER {
        del=0   (ms)
        dur=10000   (ms)
    		
		ip1=-1 (nA)
		ip2=-0.503 (nA)
		ip3=0 (nA)
		ip4=0 (nA)
		ip5=0 (nA)
			
		pon1=0 (ms)
		pon2=4000 (ms)
		pon3=5000 (ms)
		pon4=7000 (ms)
		pon5=9000 (ms)
			
		poff1=4000 (ms)
		poff2=16000 (ms)
		poff3=9000 (ms)
		poff4=7200 (ms)
		poff5=9200 (ms)
			
		i0=0 (nA)
		s=1			
    }

    ASSIGNED {
        i (nA)
    }

    BREAKPOINT {
        at_time(del)
        at_time(del + dur)
		
		i = i0 + s*((heav(poff1-t)*heav(t-pon1)*ip1) + (heav(poff2-t)*heav(t-pon2)*ip2-0.01) + (heav(poff3-t)*heav(t-pon3)*ip3) + (heav(poff4-t)*heav(t-pon4)*ip4) + (heav(poff5-t)*heav(t-pon5)*ip5))
    }
	
	FUNCTION heav (x) {
		if (x < 0) {heav = 0}
		else {heav = 1}
	}

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