June 2006
Volume 6, Issue 6
Free
Meeting Abstract  |   June 2006
Brain responses to global perceptual coherence
Author Affiliations
  • Oliver J. Braddick
    Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK
  • Dee Birtles
    Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK, and Visual Development Unit, Dept of Psychology, University College London, Gower St, London WC1E 6BT
  • Susanna Mills
    Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK
  • Julien Warshafsky
    Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK
  • John Wattam-Bell
    Visual Development Unit, Dept of Psychology, University College London, Gower St, London WC1E 6BT
  • Janette Atkinson
    Visual Development Unit, Dept of Psychology, University College London, Gower St, London WC1E 6BT
Journal of Vision June 2006, Vol.6, 426. doi:10.1167/6.6.426
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      Oliver J. Braddick, Dee Birtles, Susanna Mills, Julien Warshafsky, John Wattam-Bell, Janette Atkinson; Brain responses to global perceptual coherence. Journal of Vision 2006;6(6):426. doi: 10.1167/6.6.426.

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      © 2015 Association for Research in Vision and Ophthalmology.

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Abstract

Coherence thresholds for concentric patterns of contour segments or dot trajectories have revealed differential development and vulnerability of extrastriate form and motion pathways respectively (Braddick et al, Neuropsychologia, 2003). Here we explore the properties of visual evoked potentials (VEPs) specific to form and motion coherence. Coherent contour or motion arrays alternate with incoherent arrays at 0.5–4 Hz. A 2nd harmonic VEP signal (F2) may arise from local changes occuring at each transition, but a first harmonic (F1) must reflect differential responses to coherence and incoherence, indicating global processing.

F1 amplitude is approximately linear with coherence for both form and motion, confirming that F1 measures global processing. F2 is independent of coherence for form, and nearly so for motion, implying that it reflects local changes. Occipital F1 amplitudes for motion:form coherence are approximately 2:1. However, this does not reflect underlying sensitivity: psychophysical form and motion coherence thresholds are similar, and extrapolation of the linear region of F1 amplitude vs coherence reaches zero close to threshold coherence in each case.

F1 amplitude for both displays increases gradually from 0.5–4 Hz. However, this is opposite to psychophysical coherence sensitivity, which falls over the same range.

We conclude: (a) coherence-dependent VEPs provide measures of global form and motion processing, practical for infants and non-verbal (e.g. autistic) children; (b) this response is elicited efficiently at relatively high presentation rates; (c) the level tapped by the VEP does not provide the limiting factor on temporal integration in global perceptual processing.

Braddick, O. J. Birtles, D. Mills, S. Warshafsky, J. Wattam-Bell, J. Atkinson, J. (2006). Brain responses to global perceptual coherence [Abstract]. Journal of Vision, 6(6):426, 426a, http://journalofvision.org/6/6/426/, doi:10.1167/6.6.426. [CrossRef]
Footnotes
 Supported by MRC programme grant G7908507
© 2006 ARVO
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