Neuron Model Properties

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Figure 1. Spiking neuron properties window.

All the neurons in this module are derived from the Node object and share the properties of that item. For a description of these properties please see the text that discusses the Node properties.

Bursting (Ca) Properties
Bursting is modeled using an inactivating slow calcium current. If you do not wish the neuron to show bursting or plateau properties, set the maximum Ca conductance to 0, and ignore the remaining Ca properties.

Maximum Ca conductance
This sets the Ca conductance when all Ca channels are fully activated. A value of 15 will induce endogenous bursting if the other parameters are left at their default values.
Default value: 0 uS. Acceptable range: 0 to 100 uS.

Activation mid-point
This sets the voltage at which, after allowing sufficient time to achieve steady state, the Ca activation variable has a value of 0.5.
Default value: -30 mV. Acceptable range: -200 to 200 mV.

Activation slope
This sets the slope of the Ca activation variable against voltage, at the mid-point.
Default value: 0.1. Acceptable range: 0.01 to 10.

Activation time constant
This sets the maximum rate (time constant) with which the activation variable achieves a new value after a change in voltage. The actual time constant is itself voltage-dependent, following a Gaussian distribution with a peak value (this parameter) at the voltage of the activation variable mid-point, and the same slope as the activation variable.
Default value: 20 ms. Acceptable range: 1 to 100000 ms.

Inactivation mid-point
This is similar to the activation mid-point, but works to inactivate the calcium current.
Default value: -90 mV. Acceptable range: -200 to 200 mV.

Inactivation slope
This is similar to the activation slope, but works to inactivate the calcium current.
Default value: -0.1. Acceptable range: -0.01 to -10.

Inactivation time constant
This is similar to the activation time constant, but works to inactivate the calcium current.
Default value: 7500 ms. Acceptable range: 1 to 100000 ms.

Accommodation time constant
This sets the rate at which the threshold adjusts to its new value as the membrane potential changes.
Default value: 10 ms. Acceptable range: 1 to 1000 ms.

AHP conductance
This sets the value of the conductance increase which occurs immediately following a spike.
Default value: 1 uS. Acceptable range: 0 to 100 uS.

AHP time constant
This sets the rate at which the conductance increase which follows a spike decays.
Default value: 3 ms. Acceptable range: 1 to 100 ms.

Description
This is a text area where you can enter a detailed description of this neuron. When a user moves the mouse over this neuron a pop-up window will be briefly displayed that shows this descriptive text. This area is very useful for annotizing the parts of your circuit. For example, we are using it to keep track of which neurons in our circuits are based on real physiological data, and which are simply speculative. You can also add standard link descriptors in the text like ftp:\\, http:\\, and file:\\ for locations on your harddrive. This allows you to link a neuron or synapse to documents on the internet that describe it in detail.

Enabled
If this is false then it as if this neuron is no longer a part of the network. It does not process any incoming inputs and does not produce spikes or outputs.
Default value: -40 mV. Acceptable range: -100 to -1 mV.

Initial threshold
This is the threshold prior to any spike threshold accommodation that may occur.
Default value: -40 mV. Acceptable range: -100 to -1 mV.

Name
This is the name of this neuron that will be displayed within its node in the diagram.
Neuron Type
This is a read-only description of the type of this neuron. It can be spiking or non-spiking.
Relative accommodation
This sets the degree to which the spike threshold accommodates (increases) in response to depolarization. A value of 0 means no accommodation (threshold constant). A value of 1 means that when the membrane potential changes, the steady-state threshold (i.e. the threshold when the membrane potential has remained at its new level for a long period of time) exactly parallels the membrane potential: it remains as far above the membrane potential as it was in the resting condition.
Default value: 0.3. Acceptable range: 0 to 1.

Resting potential
This is the membrane potential in the absence of any stimulus or synaptic input:
Default value: -60 mV. Acceptable range: -100 to -20 mV.

Constant current stimulus
This is a constant current which will be injected into this neuron. Default value: 0 nA. Acceptable range: -1000 to 1000 nA.

Noise
This causes random (uniform distribution) changes in membrane potential within the limits set by this parameter. This is useful to prevent metastable output patterns, and does not slow the simulation as much as using random synaptic input (see below).
Default value: 0 mV. Acceptable range: 0 to 5 mV.

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