BTDP synaptic plasticity rule

To update weights between HVC_RA neurons, we used a BTDP rule based on the burst onset timing between the presynaptic and the postsynaptic neurons (Fig 4A). We defined a “burst” as a continuous group of spikes with duration 30 ms or less. Burst onset time was defined as the first spike in a burst. Each time a neuron produced a new burst, all afferent synapses onto the neuron and all efferent synapses are updated. For a pair of a presynaptic neuron i with burst onset time t_i and a postsynaptic neuron j with burst onset time t_j, an additive LTP would occur for the synapse with weight G_ij if Δt = t_j − t_i > T₀:

If Δt ≤ T₀, the synapse undergoes depression through multiplicative LTD:

The following parameters were used in simulations unless specified: A_P = 0.25 nS, A_D = 0.02, T₀ = 2 ms, T_P = 3 ms, T_D = 3 ms, τ_P = 30 ms, τ_D = 30 ms. All weights were clipped below G_min = 0 nS and above G_max = 4 nS.