From hearing to singing:sensory to motor information processing in the grasshopper brain

by Mit Balvantray Bhavsar

Institution: Georg-August-Universität Göttingen
Year: 2016
Posted: 02/05/2017
Record ID: 2135321
Full text PDF: http://hdl.handle.net/11858/00-1735-0000-0028-87E6-0


Grasshoppers, and among them especially the species Chorthippus biguttulus, have been used as a model system to study the neuronal basis of acoustic behavior. Auditory neurons have been described from intracellular recordings. The growing interest to study population activity of neurons has been satisfied so far with artificially combining data from different individuals. Here for the first time multielectrode recordings from the brain of a small grasshopper brain were made. Three 12 µm tungsten wires (combined in a multielectrode) to record from local brain neurons and from a population of auditory neurons entering the brain from the thorax. It was possible to separate up to five units by sorting algorithms. Tungsten wires exhibited stable recordings with higher signal-to-noise ratio than copper wires. Due to the tight temporal coupling of auditory activity to the stimulus spike collisions were frequent and collision analysis retrieved 10–15% of additional spikes. Physiological identification of units described from intracellular recordings was hard to achieve therefore the focus was on comparing individual units. Recording the population activity of auditory neurons in one individual prevents interindividual and trial-to-trial variability which otherwise reduce the validity of the analysis. Decoding the information about the acoustic stimulus was compared between single neurons and set of simultaneously recorded neurons. Information was higher for some data sets with 2 or more simultaneously recorded neurons indicating the existence of a population code inside the brain of grasshopper. Local brain neurons were recorded from lateral protocerebrum, anterior brain and central complex and were separated from ascending neurons based on their longer latencies. One local brain neuron was found discriminating between behaviorally attractive and non-attractive stimuli. Using such multielectrodes, it was also possible to induce singing responses by electrically stimulating different auditory neuropiles in the brain of grasshoppers. Advisors/Committee Members: Stumpner, Andreas (advisor), Stumpner, Andreas (referee), Heinrich, Ralf (referee).