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Journal of the Optical Society of America A

Journal of the Optical Society of America A

| OPTICS, IMAGE SCIENCE, AND VISION

  • Vol. 19, Iss. 4 — Apr. 1, 2002
  • pp: 678–686

Role of synchrony in contour binding: some transient doubts sustained

Steven C. Dakin and Peter J. Bex  »View Author Affiliations


JOSA A, Vol. 19, Issue 4, pp. 678-686 (2002)
http://dx.doi.org/10.1364/JOSAA.19.000678


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Abstract

The temporal correlation hypothesis proposes that neurons signal mutual inclusion in complex features, such as extended contours, by phase-locking their firing [GrayC. M.SingerW., Proc. Natl. Acad. Sci. USA 86, 1698 (1989)]. Although this hypothesis remains controversial, a number of recent psychophysical studies have suggested that temporal correlation among features can indeed promote perceptual grouping. In particular, subjects are better at detecting extended visual contours embedded within a field of distractor elements when a small delay is present between a cycling presentation of the contour and the background [Nature 394, 179 (1988)]. We have replicated this finding and examined three potentially confounding factors. First, we controlled local density and used more curved contours composed of bandpass elements to confirm that the effect was associated with contour integration and not with the operation of coarse-scale spatial filters. Second, we minimized the effects of saccadic eye movements (which could combine with the flicker of the asynchronous display to introduce motion cues at the contour location) both by using a fixation marker that was visible only when observers made a saccade (allowing them to reject these trials) and by retinally stabilizing the stimulus. We report that eye movements contribute to the effect. Third, we asked if either visible persistence or transients at the onset and the offset of the asynchronous stimuli might contribute to the effect. We report that the effect is largely abolished by the inclusion of prestimulus and poststimulus masks and is entirely abolished by ramping the contrast of the stimulus on and off. Neither ramping, masking, nor stabilization should specifically disrupt a contour-binding scheme based on temporal synchrony, and we conclude that it is the transient component at the onset and the offset of these stimuli that is responsible for the reported advantage for asynchronous presentation.

© 2002 Optical Society of America

OCIS Codes
(330.5000) Vision, color, and visual optics : Vision - patterns and recognition
(330.5510) Vision, color, and visual optics : Psychophysics

History
Original Manuscript: August 2, 2001
Revised Manuscript: September 24, 2001
Manuscript Accepted: September 19, 2001
Published: April 1, 2002

Citation
Steven C. Dakin and Peter J. Bex, "Role of synchrony in contour binding: some transient doubts sustained," J. Opt. Soc. Am. A 19, 678-686 (2002)
http://www.opticsinfobase.org/josaa/abstract.cfm?URI=josaa-19-4-678

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