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;
// This is the NEURON startup file for the motoneuron model set
{load_file("nrngui.hoc")}

// NOTE: this init file must be executed from a directory containing
// the hoc files specifying parameters for one or more motoneuron models


strdef startloc, codeloc, myfile
DEBUG=0
strdef start_dir
start_dir = getcwd()

// code location is 1 directory up, under the "code" directory
startloc = getcwd()
{sprint(codeloc, "%s../code", codeloc)}

type = unix_mac_pc()
{sprint(codeloc, "%s../code", startloc)}
if (type == 3) { // this is a mswin PC
    {sprint(myfile, "%s/nrnmech.dll", codeloc)}
} else { // this is a unix OS
    //    {sprint(myfile, "%s/i686/.libs/libnrnmech.so", codeloc)}
    {sprint(myfile, "%s/umac/.libs/libnrnmech.so", codeloc)}
}    
// load the compiled dll
{nrn_load_dll(myfile)}

// Base code
{sprint(myfile, "%s/FRMotoneuronNaHH.hoc", codeloc)}
{xopen(myfile)}

// GUI to select stuff to run. This is in the code directory
{sprint(myfile, "%s/GUI_FR_analysis.hoc", codeloc)}
{load_file(myfile)}

// file to generate small current pulses for passive analysis
{sprint(myfile, "%s/ana_passive.hoc", codeloc)}
{load_file(myfile)}

// file to record/analyze AP, AHP
{sprint(myfile, "%s/RecActive.hoc", codeloc)}
{load_file(myfile)}

// file to generate current ramps for frequency-current plots
{sprint(myfile, "%s/ana_FI.hoc", codeloc)}
{load_file(myfile)}

// file to generate voltage ramps for frequency-current plots
{sprint(myfile, "%s/ana_vc_synss.hoc", codeloc)}
{load_file(myfile)}

// file to generate conductance ramps
{sprint(myfile, "%s/ana_G.hoc", codeloc)}
{load_file(myfile)}