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 low threshold potassium channels in VCN auditory neurons 
: k_LT=glt*w^4*z*(v-Ek)
: based on Rothman and Manis (2003c)
: Modifications by Yi Zhou for an MSO model

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

NEURON {
	SUFFIX kLT_VCN2003
	USEION k READ ek WRITE ik
	RANGE gkbar 
	RANGE w_inf,z_inf
	RANGE tau_w,tau_z
	RANGE w_exp,z_exp
	RANGE ik,gk
	
}


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

PARAMETER {
	gkbar	= 0.04	(mho/cm2)  
	ek=-70		(mV) 
	celsius =22		(degC)
	dt              (ms)
	v               (mV)
	
}

STATE {
	w z
}

ASSIGNED {
	gk(mho/cm2)
	ik(mA/cm2)
	w_inf
	z_inf
	tau_w
	tau_z
	w_exp
	z_exp
	tadj
}


BREAKPOINT {
	SOLVE states
	gk=gkbar *w^4*z
	ik  = gk*(v-ek)
}



PROCEDURE states() {	: this discretized form is more stable
	evaluate_fct(v)
	w = w + w_exp * (w_inf - w)
	z = z + z_exp * (z_inf - z)
	VERBATIM
	return 0;
	ENDVERBATIM
}

UNITSOFF
INITIAL {
:
:  Q10 was assumed to be 3 for both currents
:
	tadj = 3.0 ^ ((celsius-22)/ 10 )
	evaluate_fct(v)
	w= w_inf
	z= z_inf
	}

PROCEDURE evaluate_fct(v(mV)) {LOCAL h
	
	tau_w = (100/(6*exp((v+60)/6)+16*exp(-(v+60)/45))+1.5)/ tadj
	w_inf = 1/(1+exp(-(v+48)/6))^0.25
        
	tau_z = (1000/(exp((v+60)/20)+exp(-(v+60)/8))+50)/ tadj
	h=0.5
	z_inf = (1-h)/(1+exp((v+71)/10))+h
	
	w_exp = 1 - exp(-dt/tau_w)
	z_exp = 1 - exp(-dt/tau_z)
	
}

UNITSON

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