Investigating local network interactions underlying first and second-order processing

D Ellemberg, Harriet Allen, RF Hess

Research output: Contribution to journalArticle

29 Citations (Scopus)


We compared the spatial lateral interactions for first-order cues to those for second-order cues, and investigated spatial interactions between these two types of cues. We measured the apparent modulation depth of a target Gabor at fixation, in the presence and the absence of horizontally flanking Gabors. The Gabors' gratings were either added to (first-order) or multiplied with (second-order) binary 2-D noise. Apparent "contrast" or modulation depth (i.e., the perceived difference between the high and low luminance regions for the first-order stimulus, or between the high and low contrast regions for the second-order stimulus) was measured with a modulation depth-matching paradigm. For each observer, the first- and second-order Gabors were equated for apparent modulation depth without the flankers. Our results indicate that at the smallest inter-element spacing, the perceived reduction in modulation depth is significantly smaller for the second-order than for the first-order stimuli. Further, lateral interactions operate over shorter distances and the spatial frequency and orientation tuning of the suppression effect are broader for second- than first-order stimuli. Finally, first- and second-order information interact in an asymmetrical fashion; second-order flankers do not reduce the apparent modulation depth of the first-order target, whilst first-order flankers reduce the apparent modulation depth of the second-order target.
Original languageEnglish
Pages (from-to)1787-1797
Number of pages11
JournalVision Research
Issue number15
Early online date27 Mar 2004
Publication statusPublished - 27 Mar 2004


  • second-order
  • first-order
  • spatial lateral interactions
  • apparent contrast
  • apparent modulation depth


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