A model for interaural time difference sensitivity in the medial superior olive (Zhou et al 2005)

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Accession:53869
This model simulates responses of neurons to interaural time difference (ITD) in the medial superior olive (MSO) of the mammalian brainstem. The model has a bipolar cell structure and incorporates two anatomic observations in the MSO: (1) the axon arises from the dendrite that receives ipsilateral inputs and (2) inhibitory synapses are located primarily on the soma in adult animals. Fine adjustment of the best ITD is achieved by the interplay of somatic sodium currents and synaptic inhibitory currents. The model suggests a mechanism for dynamically "fine-tuning" the ITD sensitivity of MSO cells by the opponency between depolarizing sodium currents and hyperpolarizing inhibitory currents.
Reference:
1 . Zhou Y, Carney LH, Colburn HS (2005) A model for interaural time difference sensitivity in the medial superior olive: interaction of excitatory and inhibitory synaptic inputs, channel dynamics, and cellular morphology. J Neurosci 25:3046-58 [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:
Cell Type(s): Medial Superior Olive (MSO) cell;
Channel(s): I h; I Sodium; I Potassium;
Gap Junctions:
Receptor(s): AMPA; Glycine;
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Coincidence Detection; Axonal Action Potentials;
Implementer(s): Zhou, Yi [yizhou at bu.edu];
Search NeuronDB for information about:  AMPA; Glycine; I h; I Sodium; I Potassium;
TITLE Na channels in VCN auditory neurons of guinea pig
 
: na=gna*m^3*h   
: based on Rothman and Manis 2003
: Modifications by Yi Zhou for an MSO model


INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}

NEURON {
	SUFFIX na_VCN2003
	USEION na READ ena WRITE ina
	NONSPECIFIC_CURRENT il
	RANGE gnabar 
	RANGE m_inf,h_inf
	RANGE tau_m,tau_h
	RANGE m_exp,h_exp
	RANGE ina,gna
	RANGE gl,el
	
}


UNITS {
	(mA) = (milliamp)
	(mV) = (millivolt)
}

PARAMETER {
	gnabar	= 0.2	(mho/cm2) 
	ena=55		(mV) 
	gl= 4.0e-4	(mho/cm2)   
        el=-57		(mV)
	celsius=22 		(degC)
	dt              (ms)
	v               (mV)
	
}

STATE {
	m h
}

ASSIGNED {
	gna (mho/cm2)
	ina	(mA/cm2)
	il	(mA/cm2)
	m_inf
	h_inf
	tau_m
	tau_h
	m_exp
	h_exp
	tadj3
	
}


BREAKPOINT {
	SOLVE states
	gna=gnabar * m*m*h
	ina  = gna * (v - ena)
	il=gl*(v-el)
}



PROCEDURE states() {	: this discretized form is more stable
	evaluate_fct(v)
	m = m + m_exp * (m_inf - m)
	h = h + h_exp * (h_inf - h)
	VERBATIM
	return 0;
	ENDVERBATIM
}

UNITSOFF
INITIAL {
:
:  Q10 was assumed to be 3 for both currents
:
	tadj3 = 3.0 ^ ((celsius-22)/ 10 )
	
	evaluate_fct(v)
	m= m_inf
	h= h_inf
	}

PROCEDURE evaluate_fct(v(mV)) { 
	
	m_inf = 1 / (1+exp(-(v + 38) / 7))
    	h_inf = 1 / (1+exp((v + 65) / 6))

    	tau_m =  (10 / (5*exp((v+60) / 18) + 36*exp(-(v+60) / 25))) + 0.04
    	tau_h =  (100 / (7*exp((v+60) / 11) + 10*exp(-(v+60) / 25))) + 0.6
	
	tau_m=tau_m/tadj3	
	tau_h=tau_h/tadj3

	m_exp = 1 - exp(-dt/tau_m)
	h_exp = 1 - exp(-dt/tau_h)
	
}

UNITSON



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