Nerve cells undergo dynamic changes during development as well as after reaching maturity. During development the establishment of specific interconnected neural networks is accomplished, in part, by the removal of extraneous or inappropriate connections ("synapses"). Similar structural changes in synapses ("plasticity") can also occur in the mature nervous system following appropriate environmental stimuli including those associated with learning and memory. The research technique involves the use of a simple culture system of nerve cells isolated from the marine invertebrate, Aplysia. Using this model system one can examine whether common mechanisms are responsible for synapse elimination during development and synapse plasticity under conditions which simulate learning and memory in the adult. One important advantage of this model system is that changes in the same set of connections can be compared during development and in the mature nervous system. An understanding of these mechanisms may provide insight into process of development of the nervous system and abnormalities which may occur in adults.