Integrate and Fire Cells
Integrate and Fore cell models are characterized by a threshold.....
A simple IaFCell specification looks like:<IaFCell id="iaf1" capacitance="3pF" threshold="-45mV" reset_potentail="-70mv" refractory_period="5ms"> </IaFCell>
This defines a cell model which will generate a spike when the potential crosses -45mV from below. The potental is then reset to -70mV and held there for 5ms before it begins to integrate again.
Without any input, however there is nothing to cause the potential to change. The cell can have one or more populations of synapses refereing to separate synapse models:
<IaFCell id="iaf2" capacitance="0.04nF" threshold="-45mV" reset_potentail="--0.07V" refractory_period="0.01s"> <SynapseSet synapse="syn1" number="50" /> <SynapseSet synapse="syn2" number="50" /> </IaFCell>
The cell may also containany combiantion of membrane channels. Since there is not concept of area for an IaFCell, the channels are expressed by total number rather than by their surface density.
<IaFCell id="iaf2" capacitance="3pF" threshold="-0.45V" reset_potentail="-70mV" refractory_period="0.04s"> <SynapseSet synapse="syn1" number="50" /> <SynapseSet synapse="syn2" number="50" /> <ChannelSet channel="Ca_t" number="3400" /> <ChannelSet channel="H1" number="800" /> </IaFCell>
IaFCell |
Simple Integrate and Fire cell with a capacitance and a threshold |
Standalone model |
An Integrate and Fire cell defined by a capacitance, threshold, reset potentialrefractory period and optional leak timescale. Channel populations can be included in the cell with conductance, current or charge based synapses. Note that the leak timescale, is simply a convenience and is equivalent to adding a population of non-gated channels with reversal potential Vrest.
Attributes
| Name | Type | Definition | Units | Range | Required |
|---|---|---|---|---|---|
| id | identifier | Identifier for the cell type; unique within the model | yes | ||
| capacitance | Floating point value | Capacitance of the cell. IaF cells are point-like with surface area. To use the standard channel distribution components on an Integrate and Fire cell, use the SphericalIaFCell | pF | (0.1, 100) | yes |
| reset_potential | Floating point value | Potential to which the cell is reset after a spike | mV | (-80, -50) | yes |
| threshold | Floating point value | Threshold for generating a spike. | mV | (-60, -20) | yes |
| refractory_period | Floating point value | After a spike, the membrane potential is held at the reset potential for the refractory_period. Synaptic input and channel currents have no effect, though ongoing synaptic conductances from events that arrived during the refractory period will have an effect once the refractory period expires. | ms | (0.1, 10) | |
| leak_timescale | Floating point value | Convenience parameter for creating a leaky cell model. It adds a conductance that reverses at the reset potential with magnitude capacitance / leak_timescale | ms | (1, 100) |
Elements
| Element type | Role |
|---|---|
| ChannelSet | channel sets |
| SynapseSet | synapse sets |
ChannelSet |
Population of channels for an IaFCell |
within: IaFCell |
A population of channels for an IaF cell. It just requires the channel type and the number of channels.
Attributes
| Name | Type | Definition | Units | Range | Required |
|---|---|---|---|---|---|
| channel | identifier reference | The channel type (KSChannel) | yes | ||
| number | Whole number | Total number of channels in the population | [0, 10^6) |
Elements - No child elements are allowed
SynapseSet |
Population of synapse for an IaFCell |
within: IaFCell |
A population of synapses for an IaF cell. The synapse reference can point to a conductance based or current based synapse model
Attributes
| Name | Type | Definition | Units | Range | Required |
|---|---|---|---|---|---|
| synapse | identifier reference | The synapse type (Synapse) | yes | ||
| number | Whole number | Total number of channels in the population | [0, 10^6) |
Elements - No child elements are allowed