Struct Synapse 

pub struct Synapse {
    pub pre_neuron: usize,
    pub post_neuron: usize,
    /* private fields */
}

Synaptic connection with STDP learning

This synapse implements spike-timing dependent plasticity (STDP), a fundamental learning rule in biological neural networks. The synaptic strength is modified based on the relative timing of pre- and post-synaptic spikes.

STDP Rule

• If pre-synaptic spike occurs before post-synaptic spike: potentiation (strengthening)
• If post-synaptic spike occurs before pre-synaptic spike: depression (weakening)
• The magnitude of change decreases exponentially with the time difference

Example

use scirs2_spatial::neuromorphic::core::Synapse;

let mut synapse = Synapse::new(0, 1, 0.5);

// Simulate STDP learning
synapse.update_stdp(10.0, true, false);  // Pre-synaptic spike at t=10
synapse.update_stdp(15.0, false, true);  // Post-synaptic spike at t=15

println!("Updated weight: {}", synapse.weight()); // Should be increased

Fields

pre_neuron: usize

Pre-synaptic neuron ID

post_neuron: usize

Post-synaptic neuron ID

Implementations

impl Synapse

pub fn new(pre_neuron: usize, post_neuron: usize, initial_weight: f64) -> Self

Create new synapse

Arguments

• pre_neuron - ID of pre-synaptic neuron
• post_neuron - ID of post-synaptic neuron
• initial_weight - Initial synaptic weight

Returns

A new Synapse with default STDP parameters

pub fn with_stdp_params( pre_neuron: usize, post_neuron: usize, initial_weight: f64, stdp_rate: f64, stdp_tau: f64, min_weight: f64, max_weight: f64, ) -> Self

Create synapse with custom STDP parameters

Arguments

• pre_neuron - ID of pre-synaptic neuron
• post_neuron - ID of post-synaptic neuron
• initial_weight - Initial synaptic weight
• stdp_rate - STDP learning rate
• stdp_tau - STDP time constant
• min_weight - Minimum weight bound
• max_weight - Maximum weight bound

pub fn update_stdp( &mut self, current_time: f64, pre_spiked: bool, post_spiked: bool, )

Update synaptic weight using STDP rule

Applies the spike-timing dependent plasticity learning rule based on the timing of pre- and post-synaptic spikes.

Arguments

• current_time - Current simulation time
• pre_spiked - Whether pre-synaptic neuron spiked
• post_spiked - Whether post-synaptic neuron spiked

pub fn synaptic_current(&self, pre_spike_strength: f64) -> f64

Calculate synaptic current

Computes the current transmitted through this synapse given the pre-synaptic spike strength.

Arguments

• pre_spike_strength - Strength of the pre-synaptic spike

Returns

Synaptic current (weight * spike strength)

pub fn weight(&self) -> f64

Get synaptic weight

pub fn set_weight(&mut self, weight: f64)

Set synaptic weight

pub fn pre_neuron(&self) -> usize

Get pre-synaptic neuron ID

pub fn post_neuron(&self) -> usize

Get post-synaptic neuron ID

pub fn stdp_rate(&self) -> f64

Get STDP learning rate

pub fn set_stdp_rate(&mut self, rate: f64)

Set STDP learning rate

pub fn stdp_tau(&self) -> f64

Get STDP time constant

pub fn set_stdp_tau(&mut self, tau: f64)

Set STDP time constant

pub fn last_pre_spike(&self) -> f64

Get last pre-synaptic spike time

pub fn last_post_spike(&self) -> f64

Get last post-synaptic spike time

pub fn weight_bounds(&self) -> (f64, f64)

Get weight bounds

pub fn set_weight_bounds(&mut self, min_weight: f64, max_weight: f64)

Set weight bounds

pub fn is_excitatory(&self) -> bool

Check if synapse is excitatory (positive weight)

pub fn is_inhibitory(&self) -> bool

Check if synapse is inhibitory (negative weight)

pub fn reset_spike_history(&mut self)

Reset spike timing history

pub fn time_since_pre_spike(&self, current_time: f64) -> f64

Calculate time since last pre-synaptic spike

pub fn time_since_post_spike(&self, current_time: f64) -> f64

Calculate time since last post-synaptic spike

Trait Implementations

impl Clone for Synapse

fn clone(&self) -> Synapse

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Synapse

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.