stdp_nn_symm_synapse – Synapse type for spike-timing dependent plasticity with symmetric nearest-neighbour spike pairing scheme
===============================================================================================================================
Description
+++++++++++
``stdp_nn_symm_synapse`` is a connector to create synapses with spike time
dependent plasticity with the symmetric nearest-neighbour spike pairing
scheme [1]_.
When a presynaptic spike occurs, it is taken into account in the depression
part of the STDP weight change rule with the nearest preceding postsynaptic
one, and when a postsynaptic spike occurs, it is accounted in the
facilitation rule with the nearest preceding presynaptic one (instead of
pairing with all spikes, like in ``stdp_synapse``). For a clear illustration of
this scheme see fig. 7A in [2]_.
The pairs exactly coinciding (so that ``presynaptic_spike == postsynaptic_spike
+ dendritic_delay``), leading to zero ``delta_t``, are discarded. In this case the
concerned pre/postsynaptic spike is paired with the second latest preceding
post/presynaptic one (for example, ``pre=={10 ms; 20 ms}`` and ``post=={20 ms}`` will
result in a potentiation pair 20-to-10).
The implementation involves two additional variables - presynaptic and
postsynaptic traces [2]_. The presynaptic trace decays exponentially over
time with the time constant ``tau_plus`` and increases to 1 on a pre-spike
occurrence. The postsynaptic trace (implemented on the postsynaptic neuron
side) decays with the time constant ``tau_minus`` and increases to 1 on a
post-spike occurrence.
.. warning::
This synaptic plasticity rule does not take
:ref:`precise spike timing ` into
account. When calculating the weight update, the precise spike time part
of the timestamp is ignored.
Parameters
++++++++++
========= ======= ======================================================
tau_plus ms Time constant of STDP window, potentiation
(tau_minus defined in postsynaptic neuron)
lambda real Step size
alpha real Asymmetry parameter (scales depressing increments as
alpha*lambda)
mu_plus real Weight dependence exponent, potentiation
mu_minus real Weight dependence exponent, depression
Wmax real Maximum allowed weight
========= ======= ======================================================
Transmits
+++++++++
SpikeEvent
References
++++++++++
.. [1] Morrison A., Aertsen A., Diesmann M. (2007) Spike-timing dependent
plasticity in balanced random networks, Neural Comput. 19:1437--1467
.. [2] Morrison A., Diesmann M., and Gerstner W. (2008) Phenomenological
models of synaptic plasticity based on spike timing,
Biol. Cybern. 98, 459--478
See also
++++++++
:doc:`Synapse `, :doc:`Spike-Timing-Dependent Plasticity `
Examples using this model
+++++++++++++++++++++++++
.. listexamples:: stdp_nn_symm_synapse