LIF¶
Here you find tools for the leaky integrate-and-fire (LIF) neuron. The module is divided into submodules corresponding to synapse types (see theory section below).
nnmt.lif.delta |
Collection of functions for LIF neurons with delta synapses. |
nnmt.lif.exp |
Collection of functions for LIF neurons with exponential synapses. |
nnmt.lif._general |
Collection of functions used by both lif.delta and lif.exp. |
Theory¶
The differential equation describing the membrane potential of the leaky integrate-and-fire (LIF) neuron is given by
with membrane time constant , synaptic current , and external current . Once the membrane voltage reaches a threshold , it is reset to the reset potential and a spike is emitted.
See Fourcaud and Brunel [2002] for more details.
Delta synapses¶
For instantaneous or delta synapses the synaptic current is given by
where the first sum runs over all synapses and the second sum over all presynaptic spikes of each synapse. is the time at which spike arrives at synapse . is the synaptic efficacy or weight of synapse .
Exponential synapses¶
For synapses with instantaneous jump and exponential decay with time constant , or just exponential synapses, the synaptic current is given by
Variables¶
Here you find how variables of LIF neurons are named in NNMT:
Quantity | Symbol | Variable name |
---|---|---|
Synaptic delay matrix | D |
|
Synaptic weight matrix | J |
|
External synaptic weight matrix | J_ext |
|
Indegree matrix | K |
|
External indegree matrix | K_ext |
|
Number of neurons | N |
|
Reset voltage | V_0 |
|
Threshold voltage | V_th |
|
Mean of synaptic input | mu |
|
Population rates | nu |
|
External population rates | nu_ext |
|
Angular frequencies | omegas |
|
Standard deviation of synaptic input | sigma |
|
Post-synaptic membrane time constant | tau_m |
|
Refractory time | tau_r |
|
Pre-synaptic time constant | tau_s |