brainpy.neurons.Izhikevich#
- class brainpy.neurons.Izhikevich(*args, input_var=True, spike_fun=None, **kwargs)[source]#
The Izhikevich neuron model.
Model Descriptions
The dynamics of the Izhikevich neuron model [1] [2] is given by:
\[ \begin{align}\begin{aligned}\frac{d V}{d t} &= 0.04 V^{2}+5 V+140-u+I\\\frac{d u}{d t} &=a(b V-u)\end{aligned}\end{align} \]\[\begin{split}\text{if} v \geq 30 \text{mV}, \text{then} \begin{cases} v \leftarrow c \\ u \leftarrow u+d \end{cases}\end{split}\]Model Examples
Model Parameters
Parameter
Init Value
Unit
Explanation
a
0.02
It determines the time scale of the recovery variable \(u\).
b
0.2
It describes the sensitivity of the recovery variable \(u\) to the sub-threshold fluctuations of the membrane potential \(v\).
c
-65
It describes the after-spike reset value of the membrane potential \(v\) caused by the fast high-threshold \(K^{+}\) conductance.
d
8
It describes after-spike reset of the recovery variable \(u\) caused by slow high-threshold \(Na^{+}\) and \(K^{+}\) conductance.
tau_ref
0
ms
Refractory period length. [ms]
V_th
30
mV
The membrane potential threshold.
Model Variables
Variables name
Initial Value
Explanation
V
-65
Membrane potential.
u
1
Recovery variable.
input
0
External and synaptic input current.
spike
False
Flag to mark whether the neuron is spiking.
refractory
False
Flag to mark whether the neuron is in refractory period.
t_last_spike
-1e7
Last spike time stamp.
References
Methods
__init__
(*args[, input_var, spike_fun])add_aft_update
(key, fun)Add the after update into this node
add_bef_update
(key, fun)Add the before update into this node
add_inp_fun
(key, fun[, label, category])Add an input function.
clear_input
()Empty function of clearing inputs.
cpu
()Move all variable into the CPU device.
cuda
()Move all variables into the GPU device.
dV
(V, t, u, I)du
(u, t, V)get_aft_update
(key)Get the after update of this node by the given
key
.get_batch_shape
([batch_size])get_bef_update
(key)Get the before update of this node by the given
key
.get_delay_data
(identifier, delay_pos, *indices)Get delay data according to the provided delay steps.
get_delay_var
(name)get_inp_fun
(key)Get the input function.
get_local_delay
(var_name, delay_name)Get the delay at the given identifier (name).
has_aft_update
(key)Whether this node has the after update of the given
key
.has_bef_update
(key)Whether this node has the before update of the given
key
.init_param
(param[, shape, sharding])Initialize parameters.
init_variable
(var_data, batch_or_mode[, ...])Initialize variables.
inv_scaling
(x[, scale])jit_step_run
(i, *args, **kwargs)The jitted step function for running.
load_state
(state_dict, **kwargs)Load states from a dictionary.
load_state_dict
(state_dict[, warn, compatible])Copy parameters and buffers from
state_dict
into this module and its descendants.nodes
([method, level, include_self])Collect all children nodes.
offset_scaling
(x[, bias, scale])register_delay
(identifier, delay_step, ...)Register delay variable.
register_implicit_nodes
(*nodes[, node_cls])register_implicit_vars
(*variables[, var_cls])register_local_delay
(var_name, delay_name[, ...])Register local relay at the given delay time.
reset
(*args, **kwargs)Reset function which reset the whole variables in the model (including its children models).
reset_local_delays
([nodes])Reset local delay variables.
reset_state
([batch_size])return_info
()save_state
(**kwargs)Save states as a dictionary.
setattr
(key, value)- rtype:
state_dict
(**kwargs)Returns a dictionary containing a whole state of the module.
std_scaling
(x[, scale])step_run
(i, *args, **kwargs)The step run function.
sum_current_inputs
(*args[, init, label])Summarize all current inputs by the defined input functions
.current_inputs
.sum_delta_inputs
(*args[, init, label])Summarize all delta inputs by the defined input functions
.delta_inputs
.sum_inputs
(*args, **kwargs)to
(device)Moves all variables into the given device.
tpu
()Move all variables into the TPU device.
tracing_variable
(name, init, shape[, ...])Initialize the variable which can be traced during computations and transformations.
train_vars
([method, level, include_self])The shortcut for retrieving all trainable variables.
tree_flatten
()Flattens the object as a PyTree.
tree_unflatten
(aux, dynamic_values)Unflatten the data to construct an object of this class.
unique_name
([name, type_])Get the unique name for this object.
update
([x])The function to specify the updating rule.
update_local_delays
([nodes])Update local delay variables.
vars
([method, level, include_self, ...])Collect all variables in this node and the children nodes.
Attributes
after_updates
before_updates
cur_inputs
current_inputs
delta_inputs
derivative
implicit_nodes
implicit_vars
mode
Mode of the model, which is useful to control the multiple behaviors of the model.
name
Name of the model.
spk_dtype
supported_modes
Supported computing modes.
varshape
The shape of variables in the neuron group.