Regularization mechanisms of spiking-bursting neurons

An essential question raised after the observation of highly variable burst ing activity in individual neurons of Central Pattern Generators (CPGs) is how an assembly of such cells can cooperatively act to produce regular sign als to motor systems. It is well known that some neurons in the lobster sto matogastric ganglion have a highly irregular spiking-bursting behavior when they are synaptically isolated from any connection in the CPG. Experimenta l recordings show that periodic stimuli on a single neuron can regulate its firing activity. Other evidence demonstrates that specific chemical and/or electrical synapses among neurons also induce the regularization of the rh ythms. In this paper we present a modeling study in which a slow subcellula r dynamics, the exchange of calcium between an intracellular store and the cytoplasm, is responsible for the origin and control of the irregular spiki ng-bursting activity. We show this in simulations of single cells under per iodic driving and in minimal networks where the cooperative activity can in duce regularization. While often neglected in the description of realistic neuron models, subcellular processes with slow dynamics may play an importa nt role in information processing and short-term memory of spiking-bursting neurons. (C) 2001 Elsevier Science Ltd. All rights reserved.