Local processing of auditory information in the thorax of Ensifera

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Acoustic signals usually are analyzed regarding carrier frequency, temporal pattern and sound direction for choosing appropriate behaviors like escape movements or approach to a potential mating partner. Many Orthoptera use acoustic signaling for intraspecific communication. For a few species of Ensifera (crickets, katydids and allies) correlates of neuronal activity to behavior have been identified. These data come nearly exclusively from intersegmental interneurons, which connect the prothoracic ganglion (site of termination of sensory neurons from the ear) with the brain. Little is known about local processing in the prothoracic ganglion of Ensifera, even though response profiles of intersegmental interneurons show manifold indications of important prothoracic processing. The only exception to this is processing of directional information by one large neuron, the omega-neuron. The current project aims at understanding behaviourally relevant temporal pattern processing and carrier frequency processing in the prothoracic ganglion of katydids. For both parameters inhibitions have been shown to play a major role in shaping neuronal properties. The local neurons evoking these inhibitions are not identified. By recording from small local neurons their morphological and physiological properties will be described. By eliminating inhibition by means of pharmacological blockers and immunohistochemical analysis of ganglia with stained neurons the contribution of these elements to (mainly) inhibitory processing will be elucidated. By photo-inactivation of a local neuron during recording from a potential postsynaptic element the contribution of single local neurons to response properties of postsynaptic cells can be shown. All in all, we want to reveal the underlying mechanisms of sound pattern and carrier frequency processing in this local network.