Auditory processing of descending neurons in the prothorax of a bush-cricket
Molecular Biology and Physiology of Neurons and Glial Cells
Final Report Abstract
For understanding the neuronal basis of behavior, one needs to know in the first place what neurons are available and suited to code for behavior in a specific species. The bush cricket Ancistrura nigrovittata became a model for the set of sensory neurons and interneurons potentially underlying their duetting behavior, which serves mate finding. On the first level of auditory processing in the prothoracic ganglion over the last 25 years sensory neurons, various local neurons, neurons with ascending axon to the brain, T-shaped neurons and a neuron ascending from the abdomen to the brain have been characterized in detail and their potential contribution to song recognition was estimated. However, one additional group, neurons with a descending axon (DN) towards the mesothorax and potentially further down has not been studied due to the problem of achieving stable recordings in their dendrites. The current project aimed at closing this gap by recording descending neurons (DN) from their cell soma situated in an anterior medial cluster, which contains about 50 cell bodies (as revealed from backfills) – very likely not all of them being auditory neurons. All of them, however, have a neurite crossing to the soma-contralateral side in the anterior part of the ganglion and have a descending axon at least to the mesothorac ganglion (see, however, “LDN” below). Only those descending neurons were studied, which are responsive to sound. One group called “lateral” due to a branch projecting laterally outside the auditory neuropil comprises likely six or more neurons with a posterior branch crossing back to the soma-side. They correspond to the typical DN known from crickets and several other bush crickets and are rather insensitive for sound, but sensitive for vibration. At least two more neurons in this class lack the back-crossing branch, but correspond otherwise to the mentioned neurons. A quite different group of DN is called “bushy” due to their dense arborization in the auditory neuropil. Their crossing neurite lies more posteriorly and at least three types of bushy DN exist as is known from combined stains. All bushy DN are auditory neurons without obvious vibratory sensitivity. Their sensitivity peaks around 10 to 25 kHz with pronounced interindividual variation. Additionally, their temporal coding properties vary from strictly phasic to phasotonic even in morphologically similar neurons indicating the possibility, that multiples with very similar morphology exist. At least one “bushy” (called DN7) receives clear inhibition at sonic frequencies and is excited in the ultrasound therefore responding to the female click, but not to the male song. One neuron, called DN9, combines properties of “lateral” and “bushy” in both respects – morphologically and physiologically. This is especially intriguing, since recent studies revealed vibratory communication by tremulation with some acoustic elements in addition when male and female A. nigrovittata are in close range. One class of descending neurons was named local descending (LDN), since most members of this class mostly have no descending axon, while others show a small abortive descending axon that never reaches the mesothoracic ganglion. These neurons are broadly sensitive to sounds from all directions and may serve as reference neurons.
Publications
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German Neuroscience Society, Göttingen 2021 (P): Auditory processing by descending neurons: a missing link in song recognition?
Cillov A. & Stumpner A.
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International Congress of Neuroethology, Lissabon 2022 (P): Filling in the gaps: auditory processing by descending neurons in a bush cricket
Cillov A. & Stumpner A.
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Local prothoracic auditory neurons in Ensifera. Frontiers in Neuroscience, 16.
Cillov, Ali & Stumpner, Andreas
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Auditory descending neurons in the prothoracic network of the bush cricket Ancistrura nigrovittata. Georg-August-Universität, Göttingen
A. Cillov
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German Neuroscience Society, Göttingen 2023 (P): Potential functions of local and descending auditory neurons in a bush cricket
Cillov A. & Stumpner A.
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Insect Sound and Vibration, London 2023 (V): Potential functions of local and descending auditory neurons in a bush cricket
Cillov A.
