1. A signal processing apparatus comprising a storage medium, the storage medium comprising a plurality of executable instructions configured to, when executed, determine plasticity rule in a spiking neuron network by at least: determination of an intra-similarity measure between outputs of neurons of a first portion of the network; determination of an inter-similarity measure between outputs of neurons of the first portion and neurons of a second portion of the network; configure the plasticity rule based on a combination of the intra-similarity and inter-similarity measure; and adjust an efficacy of one or more inhibitory connections between neurons of the network in accordance with the plasticity rule.