Measurements of long-range suppression in human opponent S-cone and achromatic luminance channels

Bei Xiao, Alex R Wade

Research output: Contribution to journalArticlepeer-review


Cortical responses to spatially discrete patches of achromatic luminance contrast can be altered by the presence of high-contrast, spatially remote "surrounds" and this achromatic "surround suppression" has been the subject of much recent research. However, the nature of long-range contrast normalization in chromatic signals has been less studied. Here we use a combination of neuroimaging data from source-imaged EEG and two different psychophysical measures of surround suppression to study contrast normalization in stimuli containing achromatic luminance and S-cone-isolating contrast. In an appearance matching task, we find strong within-channel but little between-channel suppression. However, using a contrast increment detection task, we do find evidence for weak but significant between-channel effects. Our neural measurements agree with the appearance matching data, showing significant within-channel suppression and no significant interactions between signals initiated in different pre-cortical pathways. We hypothesize that appearance judgments and V1 population responses are dominated by neurons with chromatically matched classical and extra-classical surrounds while contrast increment detection tasks rely on a subpopulation of neurons that have extra-classical surrounds sensitive to both chromatic and achromatic contrasts. Our psychophysical and source-imaged EEG results are consistent with a hypothesis based on natural scene statistics that long-range contrast normalization in early visual system is largely driven by signals within the same chromatic channel.
Original languageEnglish
Article number10
Pages (from-to)1-19
Number of pages19
JournalJournal of Vision
Issue number13
Publication statusPublished - 2010


  • Adult
  • Color Perception
  • Color Vision
  • Contrast Sensitivity
  • Discrimination (Psychology)
  • Electroencephalography
  • Evoked Potentials, Visual
  • Female
  • Humans
  • Lighting
  • Male
  • Neural Inhibition
  • Photic Stimulation
  • Psychophysics
  • Retinal Cone Photoreceptor Cells
  • Visual Fields
  • Visual Pathways

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