Structural plasticity and cortical connectivity

Kehayas, V., and Holtmaat, A. (2017). In: Van Ooyen, A., and Butz-Ostendorf, M., eds. The Rewiring Brain: A Computational Approach to Structural Plasticity in the Adult Brain. San Diego: Academic Press, pp. 3-26.

Abstract

Classic post-mortem studies of neuronal morphology have suggested that under particular physiological and pathological circumstances the physical structure of the adult brain can be altered. Neuronal morphology can change at multiple levels, ranging from the level of individual synapses to large-scale rearrangements of dendritic and axonal trees. This phenomenon has become known as neuronal structural plasticity.

Over the last two decades, these findings have been partially corroborated and expanded on by imaging studies in brain slices ex vivo and the intact brain in vivo that could monitor the morphology of neurons over time. In particular, these studies have revealed that adult cortical neurons retain the ability to continuously change their microscopic morphology, thus potentially altering the wiring diagram of the network with minimum cost. Using a multitude of experimental paradigms, researchers have probed the underlying mechanisms of structural plasticity at the level of individual synapses. Synaptic structural plasticity appears to be constrained by spatial and temporal rules, and controlled by activity-dependent and activity-independent processes. Both the spatial and temporal aspects of synaptic structural plasticity, as well as its dependence on activity, are in line with Hebb’s predictions for the formation and function of cell assemblies.

Here, we present the current state of knowledge of neuronal structural plasticity in the adult cortex and discuss its underlying mechanisms and implications for neuronal network function.