Induced gamma activity in primary visual cortex is related to luminance and not color contrast: an MEG study

Peyman Adjamian, Avgis Hadjipapas, Gareth R. Barnes, Arjan Hillebrand, Ian E. Holliday

Research output: Contribution to journalArticlepeer-review


Gamma activity in the visual cortex has been reported in numerous EEG studies of coherent and illusory figures. A dominant theme of many such findings has been that temporal synchronization in the gamma band in response to these identifiable percepts is related to perceptual binding of the common features of the stimulus. In two recent studies using magnetoencephalography (MEG) and the beamformer analysis technique, we have shown that the magnitude of induced gamma activity in visual cortex is dependent upon independent stimulus features such as spatial frequency and contrast. In particular, we showed that induced gamma activity is maximal in response to gratings of 3 cycles per degree (3 cpd) of high luminance contrast. In this work, we set out to examine stimulus contrast further by using isoluminant red/green gratings that possess color but not luminance contrast using the same cohort of subjects. We found no induced gamma activity in V1 or visual cortex in response to the isoluminant gratings in these subjects who had previously shown strong induced gamma activity in V1 for luminance contrast gratings.
Original languageEnglish
Article number4
Pages (from-to)1-7
Number of pages7
JournalJournal of Vision
Issue number7
Publication statusPublished - 20 May 2008

Bibliographical note

Creative Commons Attribution Non-Commercial No Derivatives License


  • functional imaging
  • visual cortex
  • color vision
  • magnetoencephalography
  • beamformer
  • gamma activity


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