September 2005
Volume 5, Issue 8
Free
Vision Sciences Society Annual Meeting Abstract  |   September 2005
Lateral spatial interactions for the detection of luminance-defined and contrast-defined blobs, at the fovea and in the periphery
Author Affiliations
  • Subash Sukumar
    Anglia Polytechnic University, Cambridge, UK
  • Sarah J. Waugh
    Anglia Polytechnic University, Cambridge, UK
Journal of Vision September 2005, Vol.5, 182. doi:10.1167/5.8.182
  • Views
  • Share
  • Tools
    • Alerts
      ×
      This feature is available to Subscribers Only
      Sign In or Create an Account ×
    • Get Citation

      Subash Sukumar, Sarah J. Waugh; Lateral spatial interactions for the detection of luminance-defined and contrast-defined blobs, at the fovea and in the periphery. Journal of Vision 2005;5(8):182. doi: 10.1167/5.8.182.

      Download citation file:


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

      ×
  • Supplements
Abstract

Considerable evidence supports the notion that the detection of luminance-defined and contrast-defined stimuli undergoes separate early stages in vision. In this study, we investigated lateral spatial interactions for detection, using such stimuli in the fovea and in the periphery.

Lateral spatial interaction stimuli consisted of a test blob placed between two horizontally separated flanking blobs. Blobs were either luminance-modulated (LM) or contrast-modulated (CM), constructed either by adding or multiplying random dot noise to a Gaussian profile. Modulation depth thresholds for detecting the test blob alone and in the presence of flanking blobs with 50% modulation depth, were calculated from psychometric functions generated using a self-paced, temporal 2AFC paradigm. Flanking blobs did not overlap the test blob and separations were increased up to ∼20 times the blob spread. Because larger summation areas have been found for detecting CM than LM blobs (VSS 2003), lateral interactions for different sized blobs were assessed.

At the fovea, a suppressive effect (30–80% increase in threshold) was found for both LM and CM blobs, at the closest separations between the test and the flanks. A milder facilitatory effect (15–35% decrease in threshold)was evident for greater separations.

At 5 deg in the periphery, detectability was also suppressed (25–100% increase in threshold) for both LM and CM blobs. This suppression extended over much greater spatial distances than were found at the fovea. There was no clear evidence for facilitation for larger separations in the periphery. Increasing blob size in the periphery increased the magnitude and the spatial extent of the suppression, particularly for CM stimuli.

These findings suggest that providing the stimulus size is made equivalent for both LM and CM detection systems, the nature of the underlying mechanisms for lateral spatial suppression and facilitation of detection thresholds appears similar.

Sukumar, S. Waugh, S. J. (2005). Lateral spatial interactions for the detection of luminance-defined and contrast-defined blobs, at the fovea and in the periphery [Abstract]. Journal of Vision, 5(8):182, 182a, http://journalofvision.org/5/8/182/, doi:10.1167/5.8.182. [CrossRef]
Footnotes
 APU Research Capacity Fund (SJW)
×
×

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.

×