Comparative Investigations of neuronal integration processes along the auditory pathway in simple systems

点击翻译按钮获取中文摘要

Our world is full of physical stimuli that can be detected by sensory organs and evaluated by the brain. For reproduction or survival, the detection of sound waves is essential for many animals. Neurons along the auditory pathway are informed about surrounding sounds by synaptic inputs through afferent fibres of the ear. In simple hearing systems with only low synapse levels along the auditory pathway to the brain, such as in bushcrickets, the input to prothoracic ganglion is the first important signal integration centre. The neuronal response at this level is based on the spiking of primary sensory neurons that encode spectral as well as temporal information of the sound. While frequency discrimination in the ear, which is accomplished by tonotopical travelling waves, is well understood in bushcrickets, the dynamics of the temporal encoding is still under investigation and one focus of the current proposal. In this comparative study we will investigate the neuronal integration in two different bushcricket species. Both species show sex-specific differences in mating behavior, like phonotaxis and their ears feature significantly different morphologies. In one species, Ancylecha fenestrata, the hearing organ is extensively expanded and provides an overrepresentation of behaviorally important auditory input, an auditory fovea. In total about 110 axons project to the prothoracic ganglion. The other here analyzed species, Mecopoda elongata, has only about 45 axons sending projections to the prothoracic ganglion without any overrepresentation. Our comparative study will investigate the neuronal integration process in both species and aims to gain knowledge on the advantage to build up an auditory fovea. In this project we use multielectrode and intracellular recordings in the prothoracic ganglion to investigate the neuronal integration by local field potentials in a small network, which is determined by the sound-induced signals from the bushcrickets ear, which in turn are investigated by Laser Doppler Vibrometry, intracellular recordings and neuroanatomical studies.