stdp_nn_restr_synapse – Synapse type for spike-timing dependent plasticity with restricted symmetric nearest-neighbour spike pairing scheme =========================================================================================================================================== Description +++++++++++ ``stdp_nn_restr_synapse`` is a connector to create synapses with spike time dependent plasticity with the restricted symmetric nearest-neighbour spike pairing scheme (fig. 7C in [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, but only if the latter occurred not earlier than the previous presynaptic one. When a postsynaptic spike occurs, it is accounted in the facilitation rule with the nearest preceding presynaptic one, but only if the latter occurred not earlier than the previous postsynaptic one. So, a spike can participate neither in two depression pairs nor in two potentiation pairs. 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 relies on an additional variable - the postsynaptic eligibility trace [1]_ (implemented on the postsynaptic neuron side). It decays exponentially with the time constant ``tau_minus`` and increases to 1 on a post-spike occurrence (instead of increasing by 1 as in ``stdp_synapse``). .. 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., Diesmann M., and Gerstner W. (2008) Phenomenological models of synaptic plasticity based on spike timing, Biol. Cybern. 98, 459--478 See also ++++++++ stdp_synapse, stdp_nn_symm_synapse Examples using this model +++++++++++++++++++++++++ .. listexamples:: stdp_nn_restr_synapse