Figure 1.

Different types of plasticity in the central nervous system. (A) Functional synaptic plasticity (strengthening of synaptic contacts) and structural synaptic plasticity (formation and elimination of synapses) involve modification of contacts among pre-existing elements (images inspired from [24,27]); Act, neuronal activity. Adult neurogenesis, a form of striking structural plasticity implying a change in the number of neurons, and prenatally generated neurons continuing to express molecules of immaturity for long time (“immature” neurons), are thought to provide a similar outcome through progressive maturation and, possibly, integration, thus providing examples of “whole cell structural plasticity”. (B) The main neuronal markers of immaturity (the cytoskeletal protein doublecortin, DCX, and the non-adhesive, polysialylated form of the neural cell adhesion molecule, PSA-NCAM) are co-expressed by both categories of neurons involved in whole cell structural plasticity (WCSP), namely, newly generated and non-newly generated immature neurons. Left, rabbit cerebellum; right, mouse cerebral cortex. Scale bars: 5 µm.