 A third important feature for didactic organisation in vivo concerns the spatial scale of spike propagation within a network.While it is expected that didactic organisation will always be present among neurons that exhibit spike timing-dependent plasticity and causal activity (see above), the spatial scale over which didactic organisation can occur between neurons within a network should be limited by the spatial scale of spike propagation.Evidence suggests that the scale of spike propagation can be actively controlled by adjusting the balance of excitation and inhibition within a network (a balance that can be modulated by synaptic scaling, for example), thus providing a means by which a network can actively control when and to what extent didactic organisation can occur.