Object-induced responses in blowfly motion sensitive neurons depending on discontinuities in contrast and spatial frequency content

Abstract

Event Abstract Back to Event Object-induced responses in blowfly motion sensitive neurons depending on discontinuities in contrast and spatial frequency content Thomas W. Ullrich1*, Roland Kern1 and Martin Egelhaaf1 1 Bielefeld University, Neurobiology, Germany Blowflies are a well established model system to study the neuronal processing of visual motion information. The responses of visual interneurons involved in motion information processing do not only depend on velocity but also on other stimulus parameters such as contrast or the spatial frequency content of the pattern. Whereas these dependencies are known for decades their significance for the functional role of the neurons is still unsolved. Therefore, we tested our working hypothesis that a class of these visual interneurons, the HS cells, represents in their response profiles the presence of objects in the visual field during intersaccadic intervals. Objects might be distinguished from their background by a variety of parameters such as texture, contrast, or relative motion due to an offset in depth. Since object-induced response changes in HS-cells evoked by relative motion cues were already analyzed in previous studies, we focused in separate series of experiments on objects that differed from their background by either discontinuities in brightness contrast or the spatial frequency content. We analyzed object-induced responses for movements of the blowfly encountered during intersaccadic intervals on a previously recorded free-flight trajectory (van Hateren and Schilstra, 1999). For rendering of the visual input during flight the trajectory was transferred into a computer model of a cylindrical flight arena. An object was defined by step-like variations of contrast or spatial frequency content of a random texture in a 20° wide vertical stripe, seen from the center of the cylinder. Both, polarity and size of the parameter step differed between stimuli that were tested in our high-speed panoramic stimulus device ‘FliMax’. We found strong object-induced depolarizations of the membrane potential, if the object contrast was larger than the background contrast, but not vice versa. The object evoked similar response increments when it contained higher spatial frequencies than the background, but not under reversed conditions. This asymmetry in the responses is partly a consequence of the depolarization level obtained during background motion alone. Object-induced response increments were observed as long as the response to background motion was small (e.g. for low contrast or low spatial frequency backgrounds). On the other hand, if the background motion depolarized the neuron strongly, we neither found a further depolarization of the neuron nor a substantial reduction of the depolarization level. Our results thus suggest that HS cells represent objects depending on the polarity of the difference between object and background contrast and spatial frequency content. Acknowledgements Supported by Deutsche Forschungsgemeinschaft (DFG) References van Hateren, J. H. and Schilstra, C.(1999). Blowfly flight and optic flow. II. Head movements during flight. J. Exp. Biol. 202, 1491–1500. Keywords: Blowfly, contrast, neural activity, Optic Flow, spatial discontinuity, spatial frequency, Vision Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster (but consider for student poster award) Topic: Sensory: Vision Citation: Ullrich TW, Kern R and Egelhaaf M (2012). Object-induced responses in blowfly motion sensitive neurons depending on discontinuities in contrast and spatial frequency content. Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00109 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 25 Apr 2012; Published Online: 07 Jul 2012. * Correspondence: Mr. Thomas W Ullrich, Bielefeld University, Neurobiology, Bielefeld, 33501, Germany, Ullrich_t@yahoo.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Thomas W Ullrich Roland Kern Martin Egelhaaf Google Thomas W Ullrich Roland Kern Martin Egelhaaf Google Scholar Thomas W Ullrich Roland Kern Martin Egelhaaf PubMed Thomas W Ullrich Roland Kern Martin Egelhaaf Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.