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stdp_nn_symm_synapse.h
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stdp_nn_symm_synapse.h
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/*
* stdp_nn_symm_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
* 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 STDP_NN_SYMM_SYNAPSE_H
#define STDP_NN_SYMM_SYNAPSE_H
// C++ includes:
#include <cmath>
// Includes from nestkernel:
#include "common_synapse_properties.h"
#include "connection.h"
#include "connector_model.h"
#include "event.h"
// Includes from sli:
#include "dictdatum.h"
#include "dictutils.h"
namespace nest
{
/* BeginUserDocs: synapse, spike-timing-dependent plasticity
Short description
+++++++++++++++++
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.
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
++++++++
stdp_synapse
EndUserDocs */
// connections are templates of target identifier type (used for pointer /
// target index addressing) derived from generic connection template
template < typename targetidentifierT >
class stdp_nn_symm_synapse : public Connection< targetidentifierT >
{
public:
typedef CommonSynapseProperties CommonPropertiesType;
typedef Connection< targetidentifierT > ConnectionBase;
/**
* Default Constructor.
* Sets default values for all parameters. Needed by GenericConnectorModel.
*/
stdp_nn_symm_synapse();
/**
* Copy constructor.
* Needs to be defined properly in order for GenericConnector to work.
*/
stdp_nn_symm_synapse( const stdp_nn_symm_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_steps;
using ConnectionBase::get_delay;
using ConnectionBase::get_rport;
using ConnectionBase::get_target;
/**
* Get all properties of this connection and put them into a dictionary.
*/
void get_status( DictionaryDatum& d ) const;
/**
* Set properties of this connection from the values given in dictionary.
*/
void set_status( const DictionaryDatum& d, ConnectorModel& cm );
/**
* Send an event to the receiver of this connection.
* \param e The event to send
* \param cp common properties of all synapses (empty).
*/
void send( Event& e, thread 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;
port
handles_test_event( SpikeEvent&, rport )
{
return invalid_port_;
}
};
void
check_connection( Node& s, Node& t, rport 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 norm_w = ( w / Wmax_ ) + ( lambda_ * std::pow( 1.0 - ( w / Wmax_ ), mu_plus_ ) * kplus );
return norm_w < 1.0 ? norm_w * Wmax_ : Wmax_;
}
double
depress_( double w, double kminus )
{
double norm_w = ( w / Wmax_ ) - ( alpha_ * lambda_ * std::pow( w / Wmax_, mu_minus_ ) * kminus );
return norm_w > 0.0 ? norm_w * Wmax_ : 0.0;
}
// data members of each connection
double weight_;
double tau_plus_;
double lambda_;
double alpha_;
double mu_plus_;
double mu_minus_;
double Wmax_;
double t_lastspike_;
};
/**
* Send an event to the receiver of this connection.
* \param e The event to send
* \param t The thread on which this connection is stored.
* \param cp Common properties object, containing the stdp parameters.
*/
template < typename targetidentifierT >
inline void
stdp_nn_symm_synapse< targetidentifierT >::send( Event& e, thread t, const CommonSynapseProperties& )
{
// synapse STDP depressing/facilitation dynamics
double t_spike = e.get_stamp().get_ms();
// 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;
// For a new synapse, t_lastspike_ contains the point in time of the last
// spike. So we initially read the
// history(t_last_spike - dendritic_delay, ..., T_spike-dendritic_delay]
// which increases the access counter for these entries.
// At registration, all entries' access counters of
// history[0, ..., t_last_spike - dendritic_delay] have been
// incremented by ArchivingNode::register_stdp_connection(). See bug #218 for
// details.
target->get_history( t_lastspike_ - dendritic_delay, t_spike - dendritic_delay, &start, &finish );
// facilitation due to postsynaptic spikes since the last pre-synaptic spike
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_, std::exp( minus_dt / tau_plus_ ) );
}
// depression due to the new pre-synaptic spike
double nearest_neighbor_Kminus;
double value_to_throw_away; // discard Kminus and Kminus_triplet here
target->get_K_values( t_spike - dendritic_delay, value_to_throw_away, nearest_neighbor_Kminus, value_to_throw_away );
weight_ = depress_( weight_, nearest_neighbor_Kminus );
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();
t_lastspike_ = t_spike;
}
template < typename targetidentifierT >
stdp_nn_symm_synapse< targetidentifierT >::stdp_nn_symm_synapse()
: ConnectionBase()
, weight_( 1.0 )
, tau_plus_( 20.0 )
, lambda_( 0.01 )
, alpha_( 1.0 )
, mu_plus_( 1.0 )
, mu_minus_( 1.0 )
, Wmax_( 100.0 )
, t_lastspike_( 0.0 )
{
}
template < typename targetidentifierT >
void
stdp_nn_symm_synapse< targetidentifierT >::get_status( DictionaryDatum& d ) const
{
ConnectionBase::get_status( d );
def< double >( d, names::weight, weight_ );
def< double >( d, names::tau_plus, tau_plus_ );
def< double >( d, names::lambda, lambda_ );
def< double >( d, names::alpha, alpha_ );
def< double >( d, names::mu_plus, mu_plus_ );
def< double >( d, names::mu_minus, mu_minus_ );
def< double >( d, names::Wmax, Wmax_ );
def< long >( d, names::size_of, sizeof( *this ) );
}
template < typename targetidentifierT >
void
stdp_nn_symm_synapse< targetidentifierT >::set_status( const DictionaryDatum& d, ConnectorModel& cm )
{
ConnectionBase::set_status( d, cm );
updateValue< double >( d, names::weight, weight_ );
updateValue< double >( d, names::tau_plus, tau_plus_ );
updateValue< double >( d, names::lambda, lambda_ );
updateValue< double >( d, names::alpha, alpha_ );
updateValue< double >( d, names::mu_plus, mu_plus_ );
updateValue< double >( d, names::mu_minus, mu_minus_ );
updateValue< double >( d, names::Wmax, Wmax_ );
// check if weight_ and Wmax_ have the same sign
if ( not( ( ( weight_ >= 0 ) - ( weight_ < 0 ) ) == ( ( Wmax_ >= 0 ) - ( Wmax_ < 0 ) ) ) )
{
throw BadProperty( "Weight and Wmax must have same sign." );
}
}
} // of namespace nest
#endif // of #ifndef STDP_NN_SYMM_SYNAPSE_H