The role of the Giant Fibers in visually evoked escape behavior

Abstract

Event Abstract Back to Event The role of the Giant Fibers in visually evoked escape behavior Catherine R. Von Reyn1 and Gwyneth Card1* 1 Janelia Farm Research Campus, HHMI, United States Escape behaviors are often associated with specialized large-axon command neurons (giant fibers, GFs) that trigger a fast, hard-wired motor program. Although the motor consequences of activating command neurons has been studied in some detail, it still remains unclear how command neurons and their associated circuits function in a natural context during an actual predation attempt. For example, the fruit fly, Drosophila melanogaster, has a pair of bilaterally descending GFs that serve as command neurons for a rapid escape takeoff jump. Wild-type flies takeoff in response to visual looming stimuli that mimic an approaching predator, however as yet no GF responses to looming stimuli have been observed, leading others to postulate that the GFs are not involved in these types of predation response. To address this question we developed a restrained preparation in which we could simultaneously record intracellular Drosophila GF responses to predator-like looming stimuli (see Yee et al. abstract, this conference) while monitoring the fly’s escape jump behavior. Tethered Drosophila respond to looming stimuli with a rapid mesothoracic leg extension (jump) followed by flight, though at a lower rate than in unrestrained flies. In nearly all trials, the GF depolarized in response to looming stimuli, but only in some trials did it elicit an action potential. However, there was a 1:1 correspondence between trials in which the GF fired an action potential and trials in which the fly jumped, and the GF spike consistently preceded the jump with the expected short-latency of the GF pathway. This suggests the GF is involved in the behavioral escape from natural looming stimuli. In some trials where the GF did not fire an action potential the fly still occasionally initiated flight, without any preceding jump, suggesting there is also involvement of an alternate pathway. Taking advantage of the Drosophila genetic toolkit, we anatomically identified candidates for the upstream visual inputs to the GFs that mediate the GFs looming sensitivity. LC4 neurons, which arborize in the output region of the ipsilateral optic lobe, are homologous to Col A neurons known to dye-couple with GFs in larger fly species and thus likely candidates to be presynaptic visual inputs. Synaptotagmin expressing axon terminals of LC4 neurons overlapped with GF dendrites, highly suggestive of a pre-postsynaptic interaction. These data provide evidence that both the GFs and an alternate pathway can participate in a fly’s natural response to an approaching predator by extracting visual information to generate an accurately timed jump and flight, the crucial components of escape behavior. Keywords: Drosophila, Electrophysiology, Escape, flight, Giant Fiber, loom, takeoff, 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: Sensorimotor Integration Citation: Von Reyn CR and Card G (2012). The role of the Giant Fibers in visually evoked escape behavior. Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00286 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: 03 May 2012; Published Online: 07 Jul 2012. * Correspondence: Dr. Gwyneth Card, Janelia Farm Research Campus, HHMI, Ashburn, VA, 20147, United States, cardg@janelia.hhmi.org 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 Catherine R Von Reyn Gwyneth Card Google Catherine R Von Reyn Gwyneth Card Google Scholar Catherine R Von Reyn Gwyneth Card PubMed Catherine R Von Reyn Gwyneth Card 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.