iaf_psc_alpha – Leaky integrate-and-fire neuron model with alpha-function shaped PSCs
Description
iaf_psc_alpha is an implementation of a leaky integrate-and-fire model with alpha-function shaped postsynaptic currents (PSCs). Thus, postsynaptic currents have a finite rise time.
The threshold crossing is followed by an absolute refractory period (t_ref) during which the membrane potential is clamped to the resting potential.
The linear subthreshold dynamics are integrated by the Exact Integration scheme [1]. The neuron dynamics are solved on the time grid given by the computational step size. Incoming as well as emitted spikes are forced into that grid.
An additional state variable and the corresponding differential equation represent a piecewise constant external current.
For conversion between postsynaptic potentials (PSPs) and PSCs,
please refer to the postsynaptic_potential_to_current function in
the helpers.py script of the Cortical Microcircuit model of [2].
Note
If tau_m is very close to tau_syn_ex or tau_syn_in, the model will numerically behave as if tau_m is equal to tau_syn_ex or tau_syn_in, respectively, to avoid numerical instabilities.
Parameters
The following parameters can be set in the status dictionary.
V_m_rel |
mV |
Membrane potential in mV (relative to resting potential) |
I_syn_ex |
pA |
Excitatory synaptic current |
I_syn_in |
pA |
Inhibitory synaptic current |
tau_m |
ms |
Membrane time constant |
C_m |
pF |
Capacity of the membrane |
E_L |
mV |
Resting membrane potential |
I_e |
pA |
Constant input current |
Theta_rel |
mV |
Spike threshold in mV (relative to resting potential) |
V_reset_rel |
mV |
Reset membrane potential after a spike |
tau_syn_ex |
ms |
Exponential decay time constant of excitatory synaptic current kernel |
tau_syn_in |
ms |
Exponential decay time constant of inhibitory synaptic current kernel |
t_ref |
ms |
Duration of refractory period (V_m = V_reset) |
den_delay |
ms |
Dendritic delay |