Synaptic remodeling is driven by both activity-dependent and spontaneous processes.
The magnitude of spontaneous synaptic remodeling is comparable with that of activity-dependent remodeling.
Spontaneous synaptic remodeling processes can give rise to a full repertoire of synaptic sizes even in the complete absence of activity.
While spontaneous remodeling processes drive continuous fluctuations in the properties of individual synapses, stable and skewed distributions of the same properties emerge as population invariants.
Scaling of synaptic size distributions appears as a population-level phenomenon when spontaneous remodeling processes are modulated by perturbations of spontaneous network activity.
Synaptic plasticity – the directed modulation of synaptic connections by specific activity histories or physiological signals – is believed to be a major mechanism for the modification of neuronal network function. This belief, however, has a ‘flip side’: the supposition that synapses do not change spontaneously in manners unrelated to such signals. Contrary to this supposition, recent studies reveal that synapses do change spontaneously, and to a fairly large extent. Here we review experimental results on spontaneous synaptic remodeling, its relative contributions to total synaptic remodeling, its statistical characteristics, and its physiological importance. We also address challenges it poses and avenues it opens for future experimental and theoretical research.
