THE NEURAL CELL-ADHESION MOLECULE AND SYNAPTIC PLASTICITY

Highly stereotyped patterns of neuronal connections are laid down duri ng the development of the nervous system via a range of activity indep endent and activity dependent mechanisms, Whereas the coarse hard-wiri ng of the nervous system appears to rely on molecular recognition even ts between the neuron, its pathway, and its target, the establishment of precisely patterned functional circuits is thought to be driven by neuronal activity. In this review we discuss the role that the neurona l cell adhesion molecule (NCAM) plays in morphological plasticity, Rec ent studies on NCAM and its probable species homologue in Aplysia (apC AM) suggests that an individual CAM can function to both promote synap tic plasticity and maintain the structure of the synapse, In the adult brain, changes between stability and plasticity are likely to underli e dynamic morphological changes in synaptic structures associated with learning and memory, In this review we use NCAM as an example to illu strate mechanisms that can change the function of an individual CAM fr om a molecule that promotes plasticity to one that does not. We also d iscuss evidence that NCAM promotes plasticity by activating a conventi onal signal transduction cascade, rather than by modulating adhesion p er se. Finally, we consider the evidence that supports a role for NCAM in learning and memory. (C) 1995 John Wiley and Sons, Inc.