The Roles of Experience in Different Developmental Information Stage Processes

Abstract

There are at least 3 levels of experience involvement in the specification of connections in the nervous system; connections may be experience-independent, with no detectable influence of experience on their formation, experience-expectant, where synapses are generated in advance of the experience that selects a patterned subset of them for survival, and experience-dependent, the apparent form subserving adult learning and memory, where experience appears to trigger the formation of new connections. Molecular substrates of these three types of synapse formation are probably shared to a great extent, although, when synapses are triggered by experience, there must be regulators of any gene expression involved, structural proteins expressed that can bring about synapse formation, and, we argue, a local marker, that either initiates synaptogenesis or otherwise mediates the interval between nerve cell activity and the subsequent formation of a synapse. We discuss several candidates for these roles that we have studied.