Eye movement strategies reveal spatial and temporal dynamics of contour integration
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1
University of Leuven, Laboratory of Experimental Psychology, Belgium
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2
University of Bremen, Institute for Theoretical Physics, Germany
An important task for the visual system is the grouping of local image elements into meaningful objects. One fundamental process contributing to this task is contour integration, in which collinearly aligned local edges are merged into global contours. Attempting to explain how the brain performs contour integration, Li (1998) constructed a model of contour enhancement using only known V1 elements. In this model, neural dynamics evolve over time to eventually produce a saliency map of the image, favoring locations where a contour is likely to be present. Ernst et al. (submitted) proposed an alternative, probabilistic contour integration model in which a certain amount of processing time is required before the likely contour candidate is found. Measuring eye movements can be a useful method to test the spatial and temporal dynamics of contour integration predicted by these models. We measured observers’ eye movements while searching for a global contour embedded in a background of random elements (Field, Hayes, & Hess, 1993). Observers were allowed only a limited, predefined number of eye fixations to find the contour. Contour detection performance was low when only one fixation was allowed and increased with the number of fixations, which suggests that eye movements are important for contour integration. Our data show that fixations do not appear to be random but are likely to occur on locations that are salient according to the proposed models. Currently, we are examining whether these models can account for the specific sequence of fixations over time during contour integration.
References
Ernst, U. A., Mandon, S., Schinkel-Bielefeld, N., Neitzel, S. D., Kreiter, A. K., & Pawelzik, K. R. (n.d.). Optimality of
human contour integration. Manuscript submitted for publication.
Field, D. J., Hayes, A., & Hess, R. F. (1993). Contour integration by the human visual system: Evidence for a local
“association field.” Vision Research, 33, 173-193.
Li, Z. (1998). A neural model of contour integration in the primary visual cortex. Neural Computation, 10, 903-940.
Keywords:
Eye Movements,
Psychophysics,
Visual Perception
Conference:
Neural Coding, Decision-Making & Integration in Time, Rauischholzhausen, Germany, 26 Apr - 29 Apr, 2012.
Presentation Type:
Poster Presentation
Topic:
Neural Coding, Decision-Making & Integration in Time
Citation:
Van Humbeeck
N,
Ernst
U,
Hermens
F and
Wagemans
J
(2012). Eye movement strategies reveal spatial and temporal dynamics of contour integration.
Front. Neurosci.
Conference Abstract:
Neural Coding, Decision-Making & Integration in Time.
doi: 10.3389/conf.fnins.2012.86.00008
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Received:
12 Jan 2012;
Published Online:
16 Jan 2012.
*
Correspondence:
Ms. Nathalie Van Humbeeck, University of Leuven, Laboratory of Experimental Psychology, Leuven, Belgium, nathalie.vanhumbeeck@ppw.kuleuven.be