September 2005
Volume 5, Issue 8
Free
Vision Sciences Society Annual Meeting Abstract  |   September 2005
Spatial and temporal determinants of contrast facilitation and suppression
Author Affiliations
  • John R. Cass
    Auditory Neuroscience Laboratory, Department of Physiology, Anderson Stuart Building (F13), University of Sydney, NSW 2006, Australia
  • Branka Spehar
    School of Psychology, University of New South Wales, NSW 2052, Australia
  • David Alais
    Auditory Neuroscience Laboratory, Department of Physiology, Anderson Stuart Building (F13), University of Sydney, NSW 2006, Australia
  • Roberto Arrighi
    Dipartimento di Psicologia, Università degli Studi di Firenze, Firenze, Via S. Niccolò 89, Italy
Journal of Vision September 2005, Vol.5, 459. doi:10.1167/5.8.459
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      John R. Cass, Branka Spehar, David Alais, Roberto Arrighi; Spatial and temporal determinants of contrast facilitation and suppression. Journal of Vision 2005;5(8):459. doi: 10.1167/5.8.459.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Lateral masking experiments indicate greater sensitivity to a foveal Gabor target when presented with flanking Gabors whose local carrier orientations match the target orientation. We examined the spatial and temporal determinants of this surround facilitation by measuring target contrast detection thresholds at multiple exposure durations, target-flanker SOAs and separations. Consistent with previous findings, we found maximum facilitation with synchronous collinear target-flanker onsets and offsets. Critically, the minimum exposure required to elicit facilitation increased with target-flanker separation. Transforming the visual field to human striate co-ordinates, rates of increase in facilitative delay across cortical space corresponded with the conduction velocities of long-range intra-striate connections (0.1 m/s). Contrary to previous findings (Polat & Sagi, 2004), robust suppression occurred when flanker offsets preceded target onsets, but not when the target preceded flankers. This temporally contingent suppression was evident 20ms following flanker offset at all target-flanker separations (0.6 – 1.7 degrees of visual angle), implying very fast suppressive transmission velocities, possibly due to striate-extrastriate interaction. Using circular Gaussian targets, facilitation was also maximal for synchronous presentation, but with no evidence of suppression at any SOA. These data suggest temporally dependent suppressive effects may be contingent upon local carrier information.

Cass, J. R. Spehar, B. Alais, D. Arrighi, R. (2005). Spatial and temporal determinants of contrast facilitation and suppression [Abstract]. Journal of Vision, 5(8):459, 459a, http://journalofvision.org/5/8/459/, doi:10.1167/5.8.459. [CrossRef]
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