Laguerre domain estimation of the Elementary Motion Detector based on the fly visual system

Abstract

Event Abstract Back to Event Laguerre domain estimation of the Elementary Motion Detector based on the fly visual system Egi Hidayat1, Jozi Huotari2, Alexander Medvedev1 and Karin Nordström2* 1 Uppsala University, Department of Information Technology, Sweden 2 Uppsala University, Neuroscience, Sweden Biological visual systems are generally believed to compute local motion via so called elementary motion detectors (EMDs). The EMD computes local motion by using a non-linear correlation of the luminance change from two neighboring photoreceptors after delaying the input from one. By subtracting the output from a mirror symmetric unit, direction opponency is achieved. A similar underlying computational structure is found in a range of animals, including flies, wallabies, and humans. In the fly optic ganglia, lobula plate tangential cells (LPTCs) spatially pool the output from many EMDs. The physiology of insect LPTCs, and their behavioral output, closely matches the predictions of the EMD. Importantly, however, whereas the EMD model can explain many biological observations, its neural components still remain elusive. The evidence is thus indirect. In fly motion vision research cathode ray tube (CRT) monitors are commonly used. These provide relatively high refresh rates, up to 200 Hz. Even if this is too fast for our own visual system to detect, the flicker rate is within the detection range of the fly visual system. Since the pulsatile CRT monitor refresh rate is within the fly coding range, it is coded by their photoreceptors and LPTCs. In effect, this flickering stimulus provides a unique opportunity for investigating the influence of high temporal frequencies on the underlying EMD input. We here use a CRT monitor with a refresh rate of 160 Hz on which we sinusoidally modulate a full-screen stimulus that is known to drive LPTCs strongly. We record the intracellular response of single fly photoreceptors and of LPTCs to sinusoidal gratings with different temporal and spatial frequencies. A single-tone sinusoidal grating does not provide sufficient excitation for accurate parameter estimation of a single EMD, but by adding the extra 160 Hz signal provided by the CRT refresh rate, parameter estimation from individual pulses of the neural response is possible. Note, however, that the measured signal comprises the output of several EMDs. The pulse-modulated nature of the visual stimuli due to the refresh rate of the monitor lends itself to Laguerre domain system identification. The relationship between Laguerre spectra of the input and output signals of a single EMD model has been derived and serves as a basis of its parameter estimation, see Fig 1. Further, a sparse optimization method is used to evaluate the weights and shifts of multiple EMDs contributing to a layer of EMDs that describes the measured data from LPTCs (Fig. 2). Figure 1 Figure 2 Keywords: Laguerre domain estimation, elementary motion detection (EMD), Lobula plate tangential cells (LPTCs), fly vision, motion vision Conference: Neuroinformatics 2013, Stockholm, Sweden, 27 Aug - 29 Aug, 2013. Presentation Type: Poster Topic: Electrophysiology Citation: Hidayat E, Huotari J, Medvedev A and Nordström K (2013). Laguerre domain estimation of the Elementary Motion Detector based on the fly visual system. Front. Neuroinform. Conference Abstract: Neuroinformatics 2013. doi: 10.3389/conf.fninf.2013.09.00048 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: 29 Apr 2013; Published Online: 11 Jul 2013. * Correspondence: Dr. Karin Nordström, Uppsala University, Neuroscience, Uppsala, 75124, Sweden, Karin.Nordstrom@neuro.uu.se 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 Egi Hidayat Jozi Huotari Alexander Medvedev Karin Nordström Google Egi Hidayat Jozi Huotari Alexander Medvedev Karin Nordström Google Scholar Egi Hidayat Jozi Huotari Alexander Medvedev Karin Nordström PubMed Egi Hidayat Jozi Huotari Alexander Medvedev Karin Nordström 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.