Critical periods of early visual cortex activation for abrupt and ramped object identification: a TMS study.

Abstract

Event Abstract Back to Event Critical periods of early visual cortex activation for abrupt and ramped object identification: a TMS study. Claire L. Hoysted1*, Robin Laycock1, Alexandra L. Shilton1 and Sheila Crewther1 1 La Trobe University, School of Psychological Science, Australia Although object identification is processed within the ventral visual stream, it has been recently suggested that this ventral processing can be facilitated by rapid dorsal stream feedforward/feedback activation of parietal attention mechanisms. The aim of this study was to establish critical periods of early visual cortex activation for object discrimination when dorsal/ventral or only ventral stream processing was expected. Eight participants were administered single pulse Transcranial Magnetic Stimulation (TMS) to left V2/V3 between 53ms pre- and 200ms post-stimulus onset, while completing match-to-sample object discrimination tasks. An abrupt onset/offset condition had objects presented for 67ms, which likely involves dorsal prior to ventral stream activation. The ramped condition involved contrast gradually increasing to a peak and decreasing over 334ms with the lack of transience making dorsal stream activation less likely. Objects were randomly presented in the contralateral or ipsilateral visual field. TMS disrupted object identification of stimuli presented to both the contralateral and surprisingly the ipsilateral visual field, which may be indicative of fast connections through the splenium. In the abrupt task TMS disrupted contralateral stimuli prior to object onset, and an early post onset period, and then later 200ms post object onset. TMS effects for contralateral ramped stimuli were less clear, though individual participant analysis suggested an early and late critical period of activation post object onset. Early visual cortex demonstrates a different pattern of activation depending on whether dorsal stream-driven transient attention mechanisms are likely activated, and is suggestive of feed-forward/feedback connections in early visual cortex. Keywords: Transcranial Magnetic Stimulation, Magnocellular Advantage, Visual Processing, Psychophysics, dorsal visual stream, ventral visual pathway, magnocellular system Conference: ACNS-2012 Australasian Cognitive Neuroscience Conference, Brisbane, Australia, 29 Nov - 2 Dec, 2012. Presentation Type: Poster Presentation Topic: Sensation and Perception Citation: Hoysted CL, Laycock R, Shilton AL and Crewther S (2012). Critical periods of early visual cortex activation for abrupt and ramped object identification: a TMS study.. Conference Abstract: ACNS-2012 Australasian Cognitive Neuroscience Conference. doi: 10.3389/conf.fnhum.2012.208.00046 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: 12 Oct 2012; Published Online: 07 Nov 2012. * Correspondence: Ms. Claire L Hoysted, La Trobe University, School of Psychological Science, Melbourne, Australia, clhoysted@students.latrobe.edu.au 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 Claire L Hoysted Robin Laycock Alexandra L Shilton Sheila Crewther Google Claire L Hoysted Robin Laycock Alexandra L Shilton Sheila Crewther Google Scholar Claire L Hoysted Robin Laycock Alexandra L Shilton Sheila Crewther PubMed Claire L Hoysted Robin Laycock Alexandra L Shilton Sheila Crewther 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.