Spike timing dependent plasticity (STDP) protocols.

STDP protocols used by [19] and corresponding terminology used here. For the doublet protocol, refers to the time between the pre-synaptic spike and the post-synaptic spike at each pairing. Pairings are referred to as pre-post (left) and post-pre (right). For the triplet protocol, refers to the time between the pre-synaptic spike and the second post-synaptic spike. Pairings are referred to as pre-post-post (left), post-pre-post (middle) and post-post-pre (right). The time between post-synaptic spikes is referred as to . The inter-pairing frequency is the reciprocal of the time between pairings, the inter-pairing interval. Two spike trains are depicted for pre-post-post pairings, with low (upper) and high (lower) inter-pairing frequency respectively.