CSIM: MembranePatchSimple Class Reference

MembranePatchSimple Class Reference

#include <membranepatchsimple.h>

Inheritance diagram for MembranePatchSimple:

List of all members.

Detailed Description

A a path of membrane with an arbitrary number of channels and current supplying synapses.

Model

The membrane voltage $V_m$ is governed by

$C_m \frac{V_m}{dt} = -\frac{V_m-E_m}{R_m} - \sum_{c=1}^{N_c} g_c(t) ( V_m - E_{rev}^c ) + \sum_{s=1}^{N_s} I_s(t) + I_{inject}$

with the following meanings of symbols

membrane capacity (Farad)
reversal potential of the leak current (Volts)
membrane resistance (Ohm)
total number of channels (active + synaptic)
current conductance of channel (Siemens)
$E_{rev}^c(t)$ reversal potential of channel (Volts)
total number of current supplying synapses
current supplied by synapse (Ampere)
$I_{inject}$ injected current (Ampere)

At time $t=0$ $V_m$ ist set to $V_{init}$ .

The value of $E_m$ is calculated to compensate for ionic currents such that $V_m$ actually has a resting value of $V_\mathit{resting}$ .

Spiking and reseting the membrane voltage

If the membrane voltage $V_m$ exceeds the threshold $V_{tresh}$ the MembranePatchSimple sends a spike to all its outgoing synapses.

The membrane voltage is reseted and clamped during the absolute refractory period of length $T_{refract}$ to $V_{reset}$ if the flag doReset=1. This is similar to a LIF neuron (see LifNeuron).

If the flag doReset=0 the membrane voltage is not reseted and the above equation is also applied during the absolute refractory period but the event of threshold crossing is transmitted as a spike to outgoing synapses. This is usfull if one includes channels which produce a real action potential (see HH_K_Channel and HH_Na_Channel ) but one still just wants to communicate the spikes as events in time.

Implementation

The exponential Euler method is used for numerical integration.

Public Member Functions

virtual void reset (void)
Reset the MembranePatchSimple.
virtual void IandGtot (double *i, double *g)
Calculate the new membrane voltage and check wheter Vm exceeds the threshold V_thresh.

Public Attributes

float Cm
The membrane capacity [range=(0,1); units=F;].
float Rm
The membrane resistance [units=Ohm; range=(0,1e30)].
double Em
The reversal potential of the leakage channel [readonly; units=V; range=(-1,1)].
float Vresting
The resting membrane voltage. [units=V; range=(-1,1);].
float Vinit
Initial condition for at time . [units=V; range=(-1,1);].
float VmScale
Defines the difference between Vresting and the Vthresh for the calculation of the iongate tables and the ionbuffer Erev. [units=V; range=(0,1e5);].
double Vm
The membrane voltage [readonly; units=V;].
float Inoise
Variance of the noise to be added each integration time constant. [range=(0,1); units=W^2;].
float Iinject
Constant current to be injected into the CB neuron. [units=A; range=(-1,1);].

Protected Member Functions

virtual void addChannel (IonChannel *newChannel)
Call to add a new channel.
virtual void destroyChannels (void)
Call to destroy the channels.

Protected Attributes

int nChannels
Number of channels [readonly; units=;].
int lChannels
Length of list of channels [hidden].
IonChannel ** channels
W list of associated channels [hidden].

Friends

class IonChannel
class ActiveChannel

Member Function Documentation

void MembranePatchSimple::reset ( void ) [virtual]

Reset the MembranePatchSimple.

$V_m$ is set to $V_{init}$

$E_m$ is calculated such that for no input $V_m$ relaxes to $V_{resting}$ :

$E_m = R_m \cdot \left( V_{resting} G_{tot} - I_{ch} \right)$
$G_{tot} = \frac{1}{R_m} + \sum_{c=1}^{N_c} g_\infty(V_{resting})$
$I_{ch} = \sum_{c=1}^{N_c} g_\infty(V_{resting}) E_{rev}^c$

Reimplemented in CbNeuron, and MembranePatch.

Member Data Documentation

float MembranePatchSimple::Vresting

The resting membrane voltage. [units=V; range=(-1,1);].
The value of $E_m$ is calculated to compensate for ionic currents such that $V_m$ actually has a resting value of $V_\mathit{resting}$ . This is done in reset().

last modified 07/10/2006