vogels_sprekeler_synapse.h

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/*
 *  vogels_sprekeler_synapse.h
 *
 *  This file is part of NEST.
 *
 *  Copyright (C) 2004 The NEST Initiative
 *
 *  NEST is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
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 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
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 *  You should have received a copy of the GNU General Public License
 *  along with NEST.  If not, see <http://www.gnu.org/licenses/>.
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#ifndef VOGELS_SPREKELER_SYNAPSE_H
#define VOGELS_SPREKELER_SYNAPSE_H
 
// C-header for math.h since copysign() is in C99 but not C++98
#include "connection.h"
#include <math.h>
 
namespace nest
{
 
/* BeginUserDocs: synapse, chemical, functional, stdp, Vogels
 
Short description
+++++++++++++++++
 
Synapse type for symmetric spike-timing dependent plasticity with constant depression
 
Description
+++++++++++
 
``vogels_sprekeler_synapse`` is a connector to create synapses with symmetric
spike time dependent plasticity and constant depression (as defined in :footcite:p:`Vogels2011`).
The learning rule is symmetric, that is, the synapse is strengthened
irrespective of the order of the pre- and postsynaptic spikes. Each
pre-synaptic spike also causes a constant depression of the synaptic weight
which differentiates this rule from other classical STDP rules.
 
.. warning::
 
   This synaptic plasticity rule does not take
   :ref:`precise spike timing <sim_precise_spike_times>` into
   account. When calculating the weight update, the precise spike time part
   of the timestamp is ignored.
 
Parameters
++++++++++
 
======  ======  =========================================================
 tau    ms      Time constant of STDP window, potentiation
 Wmax   real    Maximum allowed weight
 eta    real    Learning rate
 alpha  real    Constant depression (= 2 * tau * target firing rate in
                :footcite:p:`Vogels2011`)
======  ======  =========================================================
 
Transmits
+++++++++
 
SpikeEvent
 
References
++++++++++
 
.. footbibliography::
 
Examples using this model
+++++++++++++++++++++++++
 
.. listexamples:: vogels_sprekeler_synapse
 
EndUserDocs */
 
// connections are templates of target identifier type (used for pointer /
// target index addressing)
// derived from generic connection template
 
void register_vogels_sprekeler_synapse( const std::string& name );
 
template < typename targetidentifierT >
class vogels_sprekeler_synapse : public Connection< targetidentifierT >
{
 
public:
  typedef CommonSynapseProperties CommonPropertiesType;
  typedef Connection< targetidentifierT > ConnectionBase;
 
  static constexpr ConnectionModelProperties properties = ConnectionModelProperties::HAS_DELAY
    | ConnectionModelProperties::IS_PRIMARY | ConnectionModelProperties::SUPPORTS_HPC
    | ConnectionModelProperties::SUPPORTS_LBL | ConnectionModelProperties::SUPPORTS_WFR;
 
  vogels_sprekeler_synapse();
 
 
  vogels_sprekeler_synapse( const vogels_sprekeler_synapse& ) = default;
  vogels_sprekeler_synapse& operator=( const vogels_sprekeler_synapse& ) = default;
 
  // Explicitly declare all methods inherited from the dependent base
  // ConnectionBase.
  // This avoids explicit name prefixes in all places these functions are used.
  // Since ConnectionBase depends on the template parameter, they are not
  // automatically
  // found in the base class.
  using ConnectionBase::get_delay;
  using ConnectionBase::get_delay_steps;
  using ConnectionBase::get_rport;
  using ConnectionBase::get_target;
 
  void get_status( Dictionary& d ) const;
 
  void set_status( const Dictionary& d, ConnectorModel& cm );
 
  bool send( Event& e, size_t t, const CommonSynapseProperties& cp );
 
 
  class ConnTestDummyNode : public ConnTestDummyNodeBase
  {
  public:
    // Ensure proper overriding of overloaded virtual functions.
    // Return values from functions are ignored.
    using ConnTestDummyNodeBase::handles_test_event;
    size_t
    handles_test_event( SpikeEvent&, size_t ) override
    {
      return invalid_port;
    }
  };
 
  void
  check_connection( Node& s, Node& t, size_t receptor_type, const CommonPropertiesType& )
  {
    ConnTestDummyNode dummy_target;
 
    ConnectionBase::check_connection_( dummy_target, s, t, receptor_type );
 
    t.register_stdp_connection( t_lastspike_ - get_delay(), get_delay() );
  }
 
  void
  set_weight( double w )
  {
    weight_ = w;
  }
 
private:
  double
  facilitate_( double w, double kplus )
  {
    double new_w = std::abs( w ) + ( eta_ * kplus );
    return copysign( new_w < std::abs( Wmax_ ) ? new_w : Wmax_, Wmax_ );
  }
 
  double
  depress_( double w )
  {
    double new_w = std::abs( w ) - ( alpha_ * eta_ );
    return copysign( new_w > 0.0 ? new_w : 0.0, Wmax_ );
  }
 
  // data members of each connection
  double weight_;
  double tau_;
  double alpha_;
  double eta_;
  double Wmax_;
  double Kplus_;
 
  double t_lastspike_;
};
 
template < typename targetidentifierT >
constexpr ConnectionModelProperties vogels_sprekeler_synapse< targetidentifierT >::properties;
 
template < typename targetidentifierT >
inline bool
vogels_sprekeler_synapse< targetidentifierT >::send( Event& e, size_t t, const CommonSynapseProperties& )
{
  // synapse STDP depressing/facilitation dynamics
  double t_spike = e.get_stamp().get_ms();
  // t_lastspike_ = 0 initially
 
  // use accessor functions (inherited from Connection< >) to obtain delay and
  // target
  Node* target = get_target( t );
  double dendritic_delay = get_delay();
 
  // get spike history in relevant range (t1, t2] from postsynaptic neuron
  std::deque< histentry >::iterator start;
  std::deque< histentry >::iterator finish;
  target->get_history( t_lastspike_ - dendritic_delay, t_spike - dendritic_delay, &start, &finish );
 
  // presynaptic neuron j, postsynaptic neuron i
  // Facilitation for each postsynaptic spike
  // Wij = Wij + eta*xj
  double minus_dt;
  while ( start != finish )
  {
    minus_dt = t_lastspike_ - ( start->t_ + dendritic_delay );
    ++start;
    // get_history() should make sure that
    // start->t_ > t_lastspike - dendritic_delay, i.e. minus_dt < 0
    assert( minus_dt < -1.0 * kernel().connection_manager.get_stdp_eps() );
    weight_ = facilitate_( weight_, Kplus_ * std::exp( minus_dt / tau_ ) );
  }
 
  // For pre-synaptic spikes
  // Wij = Wij + eta(xi - alpha)
  // Facilitation and constant depression
  // Getting kvalue at required time already for deferred processing, so no
  // need to transform it to the current time, and so, no exponential required
  weight_ = facilitate_( weight_, target->get_K_value( t_spike - dendritic_delay ) );
  weight_ = depress_( weight_ );
 
  e.set_receiver( *target );
  e.set_weight( weight_ );
  // use accessor functions (inherited from Connection< >) to obtain delay in
  // steps and rport
  e.set_delay_steps( get_delay_steps() );
  e.set_rport( get_rport() );
  e();
 
  // exponential part for the decay, addition of one for each spike
  Kplus_ = Kplus_ * std::exp( ( t_lastspike_ - t_spike ) / tau_ ) + 1.0;
 
  t_lastspike_ = t_spike;
 
  return true;
}
 
 
template < typename targetidentifierT >
vogels_sprekeler_synapse< targetidentifierT >::vogels_sprekeler_synapse()
  : ConnectionBase()
  , weight_( 0.5 )
  , tau_( 20.0 )
  , alpha_( 0.12 )
  , eta_( 0.001 )
  , Wmax_( 1.0 )
  , Kplus_( 0.0 )
  , t_lastspike_( 0.0 )
{
}
 
template < typename targetidentifierT >
void
vogels_sprekeler_synapse< targetidentifierT >::get_status( Dictionary& d ) const
{
  ConnectionBase::get_status( d );
  d[ names::weight ] = weight_;
  d[ names::tau ] = tau_;
  d[ names::alpha ] = alpha_;
  d[ names::eta ] = eta_;
  d[ names::Wmax ] = Wmax_;
  d[ names::Kplus ] = Kplus_;
  d[ names::size_of ] = static_cast< long >( sizeof( *this ) );
}
 
template < typename targetidentifierT >
void
vogels_sprekeler_synapse< targetidentifierT >::set_status( const Dictionary& d, ConnectorModel& cm )
{
  ConnectionBase::set_status( d, cm );
  d.update_value( names::weight, weight_ );
  d.update_value( names::tau, tau_ );
  d.update_value( names::alpha, alpha_ );
  d.update_value( names::eta, eta_ );
  d.update_value( names::Wmax, Wmax_ );
  d.update_value( names::Kplus, Kplus_ );
 
  // if the weight_ is not 0, we check to ensure that weight_ and Wmax_ are of
  // the same sign
  if ( weight_ != 0 and ( std::signbit( weight_ ) != std::signbit( Wmax_ ) ) )
  {
    throw BadProperty( "Weight and Wmax must have same sign." );
  }
 
  if ( not( Kplus_ >= 0 ) )
  {
    throw BadProperty( "State Kplus must be positive." );
  }
}
}  // of namespace nest
 
#endif  // of #ifndef VOGELS_SPREKELER_SYNAPSE_H