Motion and reverse-phi stimuli that do not drive standard Fourier or non-Fourier motion mechanisms

Abstract

Event Abstract Back to Event Motion and reverse-phi stimuli that do not drive standard Fourier or non-Fourier motion mechanisms Qin Hu1* and Jonathan Victor1 1 Weill Cornell Medical College, United States Detection of motion is a crucial component of visual processing, and is generally considered to consist of two stages: an early stage in which local motion is extracted and a later stage at which local motion signals are combined into object motion or flows. Early motion processing is generally considered to be carried out by first-order (Fourier) and second-order (non-Fourier) mechanisms. Fourier motion mechanisms extract motion when the pairwise spatiotemporal correlation of luminance signal is present. Non-Fourier mechanisms are thought to work via local nonlinear pre-processing, such as flicker detection or extraction of unsigned contrast, followed by a spatiotemporal correlation of the resulting signals. To probe the computations underlying motion perception, we created a new class of non-Fourier motion stimuli: binary movies characterized by their 3rd- and 4th-order spatiotemporal correlations. As with other non-Fourier stimuli, they lack second-order correlations, and therefore their motion cannot be detected by standard Fourier mechanisms. Additionally, these stimuli lack pairwise spatiotemporal correlation of edges or flicker - and thus, also cannot be detected by extraction of one of these features, followed by standard motion analysis. Nevertheless, our psychophysical results showed that many of these stimuli produced apparent motion in human observers. The pattern of responses - i.e., which specific spatiotemporal correlations led to a percept of motion - was highly consistent across subjects. Moreover, for many of these stimuli, inverting the overall contrast of the stimulus reversed the direction of apparent motion. This "reverse phi" phenomenon, as well as the high-order-only spatiotemporal correlation of the stimulus, challenge existing models, including models that correlate low-level features (e.g., the Reichardt model and spatiotemporal energy models) and gradient models. Simple augmentations of those models - for example, spatiotemporal filters followed by non-quadratic nonlinearities - can account for some aspects of the percepts, but not for others. This suggests that a full account of motion percepts driven by high-order spatiotemporal correlations will lead to a more complete understanding of the computations underlying early motion processing. Conference: Computational and Systems Neuroscience 2010, Salt Lake City, UT, United States, 25 Feb - 2 Mar, 2010. Presentation Type: Poster Presentation Topic: Poster session III Citation: Hu Q and Victor J (2010). Motion and reverse-phi stimuli that do not drive standard Fourier or non-Fourier motion mechanisms. Front. Neurosci. Conference Abstract: Computational and Systems Neuroscience 2010. doi: 10.3389/conf.fnins.2010.03.00311 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: 08 Mar 2010; Published Online: 08 Mar 2010. * Correspondence: Qin Hu, Weill Cornell Medical College, New York, United States, qih2002@med.cornell.edu 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 Qin Hu Jonathan Victor Google Qin Hu Jonathan Victor Google Scholar Qin Hu Jonathan Victor PubMed Qin Hu Jonathan Victor 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.