# -*- coding: utf-8 -*-
from typing import Union, Callable, Optional
import jax.numpy as jnp
import brainpy.math as bm
from brainpy._src.dynold.synapses.base import _SynOut
from brainpy._src.initialize import parameter, Initializer
from brainpy.types import ArrayType
__all__ = [
'MgBlock',
]
[docs]
class MgBlock(_SynOut):
r"""Synaptic output based on Magnesium blocking.
Given the synaptic conductance, the model output the post-synaptic current with
.. math::
I_{syn}(t) = g_{\mathrm{syn}}(t) (E - V(t)) g_{\infty}(V,[{Mg}^{2+}]_{o})
where The fraction of channels :math:`g_{\infty}` that are not blocked by magnesium can be fitted to
.. math::
g_{\infty}(V,[{Mg}^{2+}]_{o}) = (1+{e}^{-\alpha V} \frac{[{Mg}^{2+}]_{o}} {\beta})^{-1}
Here :math:`[{Mg}^{2+}]_{o}` is the extracellular magnesium concentration.
Parameters
----------
E: float, ArrayType, callable, Initializer
The reversal potential for the synaptic current. [mV]
alpha: float, ArrayType
Binding constant. Default 0.062
beta: float, ArrayType, callable, Initializer
Unbinding constant. Default 3.57
cc_Mg: float, ArrayType, callable, Initializer
Concentration of Magnesium ion. Default 1.2 [mM].
name: str
The model name.
"""
[docs]
def __init__(
self,
E: Union[float, ArrayType, Callable, Initializer] = 0.,
cc_Mg: Union[float, ArrayType, Callable, Initializer] = 1.2,
alpha: Union[float, ArrayType, Callable, Initializer] = 0.062,
beta: Union[float, ArrayType, Callable, Initializer] = 3.57,
target_var: Optional[Union[str, bm.Variable]] = 'input',
membrane_var: Union[str, bm.Variable] = 'V',
name: str = None,
):
super().__init__(name=name, target_var=target_var)
self._E = E
self._cc_Mg = cc_Mg
self._alpha = alpha
self._beta = beta
self._target_var = target_var
self._membrane_var = membrane_var
def register_master(self, master):
super().register_master(master)
self.E = parameter(self._E, self.master.post.num, allow_none=False)
self.cc_Mg = parameter(self._cc_Mg, self.master.post.num, allow_none=False)
self.alpha = parameter(self._alpha, self.master.post.num, allow_none=False)
self.beta = parameter(self._beta, self.master.post.num, allow_none=False)
if isinstance(self._membrane_var, str):
if not hasattr(self.master.post, self._membrane_var):
raise KeyError(f'Post-synaptic group does not have membrane variable: {self._membrane_var}')
self.membrane_var = getattr(self.master.post, self._membrane_var)
elif isinstance(self._membrane_var, bm.Variable):
self.membrane_var = self._membrane_var
else:
raise TypeError('"membrane_var" must be instance of string or Variable. '
f'But we got {type(self._membrane_var)}')
def filter(self, g):
V = self.membrane_var.value
I = g * (self.E - V) / (1 + self.cc_Mg / self.beta * jnp.exp(-self.alpha * V))
return super(MgBlock, self).filter(I)
def clone(self):
return MgBlock(E=self._E,
cc_Mg=self._cc_Mg,
alpha=self._alpha,
beta=self._beta,
target_var=self._target_var,
membrane_var=self._membrane_var)
