SELF-ORGANIZING EFFECTS OF SPONTANEOUS NEURAL ACTIVITY ON THE DEVELOPMENT OF SPINAL LOCOMOTOR CIRCUITS IN VERTEBRATES

Presented in this paper is a neural network model that can be used to investigate the possible self-organizing mechanisms occurring during t he early ontogeny of spinal neural circuits in the vertebrate motor sy stem. The neural circuit is composed of multiple types of neurons whic h correspond to motorneurons, Renshaw cells and a hypothetical class o f interneurons. While the connectivity of this circuit is genetically predetermined, the efficacies of these connections - the synaptic stre ngths - evolve in accordance with activity-dependent mechanisms which are initiated by the intrinsic, autonomous activity present in the dev eloping spinal cord. Using Oja's rule, a modified Hebbian learning sch eme for adjusting the values of the connections, the network stably se lf-organizes developing, in the process, reciprocally activated motorn euron pools analogous to those which exist in vivo.