SPATIAL ORIENTATION OF MARINE MOLLUSK CLIONE LIMACINA

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The overall object of the proposed work is to utilize Clione as a model subject for studying the neural basis of animal behavior. The specific aim is to study neural mechanisms of spatial orientation as determined by the activity of statocyst receptors. The proposal is designed to continue ongoing work on the central mechanisms responsible for changes in statocyst information processing in different behavioral contexts, one of which involves triggering a reversal in the normal response, and two of which are believed to temporarily decrease the significance of statocyst inputs during food acquisition and during passive avoidance behavior. Statocyst cells have been identified, and their activity during varying degrees of tilt has been documented with a very clever recording system. Furthermore, central neurons which receive statocyst input, and which provide output that is capable of modifying swimming activity, have been found. The missing puzzle piece is a complete identification and thorough description of tail motoneurons which produce tail bending and thus alter the direction of swimming. This represents the first goal of the project - a thorough description of tail motoneurons. Once identified, the investigators propose to describe the cellular and synaptic mechanisms of modification of swimming and tail bending activities during different behaviors. They have chosen three behavior contexts which can be easily simulated experimentally. A reversal from positive to negative geotaxis can be triggered by simply changing temperature in the recording system. The apparent inhibition of statocyst inputs during feeding behavior will be studying by simply initiating feeding activity - the circuits involved in feeding are well known to the investigators. Finally, stimuli that trigger passive avoidance behavior can be delivered in a reduced preparation, to describe behaviorally relevant changes in activity in the steering system. Overall, the investigators propose to describe behavioral plasticity in the spatial orientation system following network modulation in behaviorally relevant contexts.