.. currentmodule:: brian

Short-term plasticity
=====================

Brian implements the short-term plasticity model described in:
Markram et al (1998). Differential signaling via the same axon of neocortical
pyramidal neurons, PNAS 95(9):5323-8.
Synaptic dynamics is described by two variables x and u, which
follows the following differential equations::

  dx/dt=(1-x)/taud  (depression)
  du/dt=(U-u)/tauf  (facilitation)

where taud, tauf are time constants and U is a parameter in 0..1.
Each a presynaptic spike triggers modifications of the variables::

  x->x*(1-u)
  u->u+U*(1-u)

Note that the update order is important. 
Synaptic weights are modulated by the product u*x (in 0..1), which is taken
before updating the variables. This model describes both depression and
facilitation.

To introduce short-term plasticity into an existing connection C, use the class
:class:`STP`::

  mystp=STP(C,taud=100*ms,tauf=5*ms,U=.6)