ht_connection.h

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/*
 *  ht_connection.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
 *  the Free Software Foundation, either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  NEST is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with NEST.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#ifndef HT_CONNECTION_H
#define HT_CONNECTION_H

#include "connection.h"

/* BeginDocumentation
  Name: ht_synapse - Synapse with depression after Hill & Tononi (2005).

  Description:
  This synapse implements the depression model described in [1, p 1678].
  Synaptic dynamics are given by

  P'(t) = ( 1 - P ) / tau_p 
  P(T+) = (1 - delta_P) P(T-)   for T : time of a spike 
  P(t=0) = 1

  w(t) = w_max * P(t)  is the resulting synaptic weight

  Parameters: 
     The following parameters can be set in the status dictionary:
     tauP     double - synaptic vesicle pool recovery time constant [ms]
     delta_P  double - fractional change in vesicle pool on incoming spikes [unitless]
     P        double - current size of the vesicle pool [unitless, 0 <= P <= 1]

  Warning:
  THIS SYNAPSE MODEL HAS NOT BEEN TESTED EXTENSIVELY!
   
  References:
   [1] S Hill and G Tononi (2005). J Neurophysiol 93:1671-1698.

  Sends: SpikeEvent

  FirstVersion: March 2009
  Author: Hans Ekkehard Plesser, based on markram_synapse
  SeeAlso: ht_neuron, tsodyks_synapse, stdp_synapse, static_synapse
*/

namespace nest {

template<typename targetidentifierT>
class HTConnection : public Connection<targetidentifierT>
{
 public:

  typedef CommonSynapseProperties CommonPropertiesType;
  typedef Connection<targetidentifierT> ConnectionBase;

  HTConnection();
  
  HTConnection(const HTConnection &);

  // 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_steps;
  using ConnectionBase::get_delay;
  using ConnectionBase::get_rport;
  using ConnectionBase::get_target;
  
  virtual ~HTConnection() {}

  virtual void get_status(DictionaryDatum & d) const;
  
  virtual void set_status(const DictionaryDatum & d, ConnectorModel &cm);

  void send(Event& e,thread t, double_t t_lastspike, 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;
    port handles_test_event(SpikeEvent&, rport) { return invalid_port_; }
  };
  
  void check_connection(Node & s, Node & t, rport receptor_type, double_t, const CommonPropertiesType &)
  {
    ConnTestDummyNode dummy_target;
    ConnectionBase::check_connection_(dummy_target, s, t, receptor_type);
  }
 
  void set_weight(double_t w) { weight_ = w; }

 private:
  double_t weight_;    

  double_t tau_P_;     
  double_t delta_P_;   

  double_t p_;         
};


template<typename targetidentifierT>
inline
void HTConnection<targetidentifierT>::send(Event& e,thread t, double_t t_lastspike, 
            const CommonSynapseProperties &)
{
  double_t h = e.get_stamp().get_ms() - t_lastspike;
  Node *target = get_target(t);
  // t_lastspike_ = 0 initially

  // propagation t_lastspike -> t_spike, t_lastspike_ = 0 initially, p_ = 1
  p_ = 1 - ( 1 - p_ ) * std::exp(-h/tau_P_);

  // send the spike to the target
  e.set_receiver(*target);
  e.set_weight( weight_ * p_ );
  e.set_delay( get_delay_steps() );
  e.set_rport( get_rport() );
  e();

  // reduce pool after spike is sent
  p_ *= ( 1 - delta_P_ );
}

template<typename targetidentifierT>
HTConnection<targetidentifierT>::HTConnection() :
    ConnectionBase(),
    weight_(1.0),
    tau_P_(50.0),
    delta_P_(0.2),
    p_(1.0)
  { }

template<typename targetidentifierT>
HTConnection<targetidentifierT>::HTConnection(const HTConnection& rhs) :
    ConnectionBase(rhs),
    weight_(rhs.weight_),
    tau_P_(rhs.tau_P_),
    delta_P_(rhs.delta_P_),
    p_(rhs.p_)
  { }

template<typename targetidentifierT>
void HTConnection<targetidentifierT>::get_status(DictionaryDatum & d) const
  {
    ConnectionBase::get_status(d);
    def<double_t>(d, names::weight, weight_);
    def<double_t>(d, "tau_P", tau_P_);
    def<double_t>(d, "delta_P", delta_P_);
    def<double_t>(d, "P", p_);
    def<long_t>(d, names::size_of, sizeof(*this));
  }

template<typename targetidentifierT>
void HTConnection<targetidentifierT>::set_status(const DictionaryDatum & d, ConnectorModel &cm)
  {
    ConnectionBase::set_status(d, cm);

    updateValue<double_t>(d, names::weight, weight_);
    updateValue<double_t>(d, "tau_P", tau_P_);
    updateValue<double_t>(d, "delta_P", delta_P_);
    updateValue<double_t>(d, "P", p_);

    if ( tau_P_ <= 0.0 ) 
      throw BadProperty("tau_P >= 0 required.");

    if ( delta_P_ < 0.0 || delta_P_ > 1.0 )
      throw BadProperty("0 <= delta_P <= 1 required.");

    if ( p_ < 0.0 || p_ > 1.0 )
      throw BadProperty("0 <= P <= 1 required.");
  }

} // namespace

#endif // HT_CONNECTION_H