In many regions of the brain, the activity-dependent changes in synaptic strength depend on the frequency and timing of presynaptic stimulation and postsynaptic activity (synaptic plasticity), as well as the history of activity at those synapses (metaplasticity). The Bienenstock, Cooper and Munro (BCM) theory made several assumptions about how synapses modify and these have helped to guide various neurobiological and neurocomputational experiments. There does appear to be a good correspondence of the synaptic plasticity and metaplasticity experimental data with the BCM model. (Fig. 1, Ref. 57.).