Mechanisms Mediating Motor Pattern Selection from a Multi-Functional Neuronal Network

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IBN-9808356 Nusbaum LAY ABSTRACT The goal of this proposal is to understand, at the cellular level, how specific rhythmic motor patterns are selected from a multifunctional neuronal network. Previous work in several invertebrate and vertebrate systems has shown that the networks generating rhythmic movements are functionally flexible. That is, the same neuronal ensemble generates distinct rhythmic motor patterns when influenced by different neuromodulatory inputs. We do not fully understand how any individual motor pattern is selected for activation from such a network. Motor pattern selection, however, is likely involve the coactivation of distinct inputs from higher centers. This and related issues regarding motor pattern selection are readily addressed in the stomatogastric nervous system. This is a very well-characterized model system that contains a set of distinct but interacting networks that generate the motor patterns underlying rhythmic contractions of striated foregut muscles involved in the ingestion, chewing and processing of food. As is true for all rhythmically active networks, these networks can still operate in the completely isolated nervous system, where all experiments will be performed. The working hypothesis is that motor pattern selection from a multifunctional neuronal network results in part from different input pathways (i.e.- different sensory systems) having distinct effects on overlapping subsets of modulatory projection neurons. To examine the validity of this hypothesis, we proposed to examine whether: (1) different input pathways evoke different motor patterns from the same network; (2) these different input pathways activate different subsets of projection neurons that influence this network; (3) different co-transmitters released by an identified sensory neuron are used to influence spatially separate neuronal targets, and (4) an individual sensory pathway exhibits an activity- dependent compartmentalization of action. Combining electrophysiological, pharmacological and anatomical approaches will attain these aims. This proposed study will provide novel physiological information regarding how the nervous system selects different motor patterns from a multifunctional neuronal network. This will be a valuable model for comparable but less accessible events occurring in the numerically more complex vertebrate nervous system. It will also provide extensive technical and intellectual training for pre- and post- doctoral students interested in the functional organization of the central nervous system.