Modulation of Synaptic Transmission and Plasticity in Nervous Systems

Summary

In recent years the study of learning and memory proceeded to an analysis on the cellular and molecular level. In some cases conditioned behaviour could be traced down to the modulation of synaptic transmission between nerve cells. Different approaches to elucidate the basic elements of the molecular mechanisms seem to converge to a unifying picture.

The genetic information for an organism must fit into every one of its cells. It is, therefore, too limited to endow an active animal with a sufficiently large repertoire of reactions to respond to a changing environment. A second system of information processing, the nervous system was developed, refined and enlarged to enormous complexity during evolution.

The brain may indeed be considered as an organ, specialized to collect, process and store information about the status of the body and about the environment and to formulate commands for appropriate interactions. The huge dimension of the task is represented in the stupendous number of nerve cells in the brain. It is, however, a simplification to see complexity only as a system property. Part of the information processing occurs already at the level of the individual nerve cell (1). While this seems to be hard to accept for some “neural network” theoreticians, it is obvious to the student of microscopic neuroanatomy who observes the diversity of size and shape of the nerve cells and yet realizes the high degree of order in the system.