The role of synaptic morphology in neural plasticity: structural interactions underlying synaptic power.

The study of synaptic plasticity has revealed a common cascade of ultrastructural events across several paradigms. Most notable of these paradigms are development, long-term potentiation (LTP), and adult reactive synaptogenesis (RS). These plastic neural events are discussed in terms of major categories of synaptic morphological change--synaptic density, curvature, and perforations, as well as the size of synaptic elements. The potential functional implications of these morphological changes are reviewed, along with considerations based on recently developed mathematical models of synaptic function. These considerations are then incorporated into the common structural alterations observed during multiple forms of synaptic activation, producing a sequential model supporting increased efficacy associated with neural plasticity. The data suggest that during a plastic challenge, synapses move through a continuum of morphological change, dependent upon the interaction of structural parameters and their effect on various aspects critical to synaptic efficacy. This complex interplay of morphological alterations and synaptic types over time and location may form a critical aspect of neural plasticity.