Human cortical responses to contrast modulations of visual noise

Julie Calvert, Velitchko Manahilov, William A. Simpson, Denis M. Parker

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


We studied visual evoked potentials (VEPs) elicited by second-order contrast modulations of binary dynamic noise and first-order luminance modulations. Using a 3-point Laplacian operator centred on Oz, we found that contrast modulations of both low and higher spatial frequencies elicited a negative component whose latency was about 200 ms. The latency of this component was significantly longer than that of the early Laplacian components to first-order luminance modulations. These findings could be due to slower first-stage linear filters and additional processing stages of the second-order pathway. The topographical analysis of scalp recorded VEPs to central and half-field stimulation has suggested that the responses to second-order patterns are likely to be generated by neuronal structures within the primary visual cortex which may have inputs from extrastriate neurons via feedback connections.

Original languageEnglish
JournalVision Research
Publication statusPublished - 1 Aug 2005


  • visual evoked potentials
  • vision sciences
  • visual cortex
  • second-order vision


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