Simulations of motor unit discharge patterns (Powers et al. 2011)

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Accession:143671
" ... To estimate the potential contributions of PIC (Persistent Inward Current) activation and synaptic input patterns to motor unit discharge patterns, we examined the responses of a set of cable motoneuron models to different patterns of excitatory and inhibitory inputs. The models were first tuned to approximate the current- and voltage-clamp responses of low- and medium-threshold spinal motoneurons studied in decerebrate cats and then driven with different patterns of excitatory and inhibitory inputs. The responses of the models to excitatory inputs reproduced a number of features of human motor unit discharge. However, the pattern of rate modulation was strongly influenced by the temporal and spatial pattern of concurrent inhibitory inputs. Thus, even though PIC activation is likely to exert a strong influence on firing rate modulation, PIC activation in combination with different patterns of excitatory and inhibitory synaptic inputs can produce a wide variety of motor unit discharge patterns."
Reference:
1 . Powers RK, Elbasiouny SM, Rymer WZ, Heckman CJ (2012) Contribution of intrinsic properties and synaptic inputs to motoneuron discharge patterns: a simulation study. J Neurophysiol 107:808-23 [PubMed]
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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:
Cell Type(s): Spinal cord lumbar motor neuron alpha ACh cell;
Channel(s):
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Activity Patterns; Bursting; Action Potentials;
Implementer(s): Powers, Randy [rkpowers at u.washington.edu];
Search NeuronDB for information about:  Spinal cord lumbar motor neuron alpha ACh cell;
//commands for generating response to pure excitatory input
xopen("Medium_thresh_MN.hoc")
SLOPE1=0.001	// slope of increase and decrease of excitatory conductance
SLOPE2=1e-7     //slope  of increase and decrease of inhibitory conductance (can't be zero)
RSTRT1=0	//background level of excitation
RSTRT2=0	//background level of inhibition
TR=20000	//total length of triangular command in milliseconds
HOLD=1000	//length of steady command at beginning and end of trial
simple2del()	//constructs excitatory and inhibitory commands
grampon()	//applies commands

//record spike times and print them out in a file
apc.record()
apc.record(spiketimes)
sprint(filename,"Medium_thresh_MN_g_0_0_0.001_1em7.txt")
init()
run()
spikeout.wopen(filename)
spiketimes.printf(spikeout,"%8.4f\n")
spikeout.close()

//responses to three differen temporal patterns of inhibiton
// when inhibition is uniformly distributed on dendrite and soma

unifinhib()

//commands for generating response to excitation with steady background inhibition
SLOPE1=0.001	
SLOPE2=1e-7     
RSTRT1=0	
RSTRT2=2	
TR=20000	
HOLD=1000	
simple2del()	
grampon()	
apc.record()
apc.record(spiketimes)
sprint(filename,"Medium_thresh_MN_g_0_2_0.001_1em7.txt")
init()
run()
spikeout.wopen(filename)
spiketimes.printf(spikeout,"%8.4f\n")
spikeout.close()

//commands for generating response to "push-pull" inhibition
SLOPE1=0.001	
SLOPE2=-0.001     
RSTRT1=0	
RSTRT2=10	
TR=20000	
HOLD=1000	
simple2del()	
grampon()	
apc.record()
apc.record(spiketimes)
sprint(filename,"Medium_thresh_MN_g_0_1_0.001_m001.txt")
init()
run()
spikeout.wopen(filename)
spiketimes.printf(spikeout,"%8.4f\n")
spikeout.close()

//commands for generating response to excitation with proportional inhibition
SLOPE1=0.001	
SLOPE2=0.001    
RSTRT1=0	
RSTRT2=2	
TR=20000	
HOLD=1000	
simple2del()	
grampon()	
apc.record()
apc.record(spiketimes)
sprint(filename,"Medium_thresh_MN_g_0_2_0.001_0.001.txt")
init()
run()
spikeout.wopen(filename)
spiketimes.printf(spikeout,"%8.4f\n")
spikeout.close()
		
//responses to three differen temporal patterns of inhibiton
// when inhibition is restricted to proximal dendrite and soma

proxinhib()

//commands for generating response to excitation with steady background inhibition
SLOPE1=0.001	
SLOPE2=1e-7     
RSTRT1=0	
RSTRT2=2	
TR=20000	
HOLD=1000	
simple2del()	
grampon()	
apc.record()
apc.record(spiketimes)
sprint(filename,"Medium_thresh_MN_gpr_0_2_0.001_1em7.txt")
init()
run()
spikeout.wopen(filename)
spiketimes.printf(spikeout,"%8.4f\n")
spikeout.close()

//commands for generating response to "push-pull" inhibition
SLOPE1=0.001	
SLOPE2=-0.001     
RSTRT1=0	
RSTRT2=10	
TR=20000	
HOLD=1000	
simple2del()	
grampon()	
apc.record()
apc.record(spiketimes)
sprint(filename,"Medium_thresh_MN_gpr_0_1_0.001_m001.txt")
init()
run()
spikeout.wopen(filename)
spiketimes.printf(spikeout,"%8.4f\n")
spikeout.close()

//commands for generating response to excitation with proportional inhibition
SLOPE1=0.001	
SLOPE2=0.001    
RSTRT1=0	
RSTRT2=2	
TR=20000	
HOLD=1000	
simple2del()	
grampon()	
apc.record()
apc.record(spiketimes)
sprint(filename,"Medium_thresh_MN_gpr_0_2_0.001_0.001.txt")
init()
run()
spikeout.wopen(filename)
spiketimes.printf(spikeout,"%8.4f\n")
spikeout.close()