# Command: stdp_facetshw_synapse_hom

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Name:

    stdp_facetshw_synapse_hom - Synapse type for spike-timing dependent
      plasticity using homogeneous parameters,
      i.e. all synapses have the same parameters.

Description:

      stdp_facetshw_synapse is a connector to create synapses with spike-timing
      dependent plasticity (as defined in [1]).
      This connector is a modified version of stdp_synapse.
      It includes constraints of the hardware developed in the FACETS (BrainScaleS)
      project [2,3], as e.g. 4-bit weight resolution, sequential updates of groups
      of synapses and reduced symmetric nearest-neighbor spike pairing scheme. For
      details see [3].
      The modified spike pairing scheme requires the calculation of tau_minus_
      within this synapse and not at the neuron site via Kplus_ like in
      stdp_connection_hom.

Parameters:

      Common properties:
      tau_plus	 double	- Time constant of STDP window, causal branch in ms
      tau_minus_stdp  double	- Time constant of STDP window, anti-causal branch
      in ms
      Wmax	 double	- Maximum allowed weight

      no_synapses	 long	- total number of synapses
      synapses_per_driver	 long	- number of synapses updated at once
      driver_readout_time	 double	- time for processing of one synapse row
      (synapse line driver)
      readout_cycle_duration	 double	- duration between two subsequent
      updates of same synapse (synapse line
      driver)
      lookuptable_0	 vector<long>	- three look-up tables (LUT)
      lookuptable_1	 vector<long>
      lookuptable_2	 vector<long>
      configbit_0	 vector<long>	- configuration bits for evaluation
      function. For details see code in
      function eval_function_ and [4]
      (configbit[0]=e_cc, ..[1]=e_ca,
      ..[2]=e_ac, ..[3]=e_aa).
      Depending on these two sets of
      configuration bits weights are updated
      according LUTs (out of three: (1,0),
      (0,1), (1,1)). For (0,0) continue
      without reset.
      configbit_1	 vector<long>
      reset_pattern	 vector<long>	- configuration bits for reset behavior.
      Two bits for each LUT (reset causal
      and acausal). In hardware only (all
      false; never reset) or (all true;
      always reset) is allowed.

      Individual properties:
      a_causal	 double	- causal and anti-causal spike pair accumulations
      a_acausal   double
      a_thresh_th  double	- two thresholds used in evaluation function.
      No common property, because variation of analog
      synapse circuitry can be applied here
      a_thresh_tl  double
      synapse_id   long  	- synapse ID, used to assign synapses to groups (synapse
      drivers)

Transmits:

    SpikeEvent

Remarks:

      The synapse IDs are assigned to each synapse in an ascending order (0,1,2,
      ...) according their first presynaptic activity and is used to group synapses
      that are updated at once. It is possible to avoid activity dependent synapse
      ID assignments by manually setting the no_synapses and the synapse_id(s)
      before running the simulation. The weights will be discretized after the
      first presynaptic activity at a synapse.

      Common properties can only be set on the synapse model using SetDefaults.

References:

      [1] Morrison, A., Diesmann, M., and Gerstner, W. (2008).
      Phenomenological models of synaptic plasticity based on
      spike-timing, Biol. Cybern., 98,459--478

      [2] Schemmel, J., Gruebl, A., Meier, K., and Mueller, E. (2006).
      Implementing synaptic plasticity in a VLSI spiking neural
      network model, In Proceedings of the 2006 International
      Joint Conference on Neural Networks, pp.1--6, IEEE Press

      [3] Pfeil, T., Potjans, T. C., Schrader, S., Potjans, W., Schemmel, J.,
      Diesmann, M., & Meier, K. (2012).
      Is a 4-bit synaptic weight resolution enough?	-
      constraints on enabling spike-timing dependent plasticity in neuromorphic
      hardware. Front. Neurosci. 6 (90).

      [4] Friedmann, S. in preparation

Author:

    Thomas Pfeil (TP), Moritz Helias, Abigail Morrison

FirstVersion:

    July 2011

SeeAlso:

- stdp_synapse
- synapsedict
- tsodyks_synapse
- static_synapse

Source:

    /opt/conda/conda-bld/nest_1510212701067/work/nest-2.14.0/models/stdp_connection_facetshw_hom.h

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