Meeren, Hanneke K. M.Hadjikhani, NouchineAhlfors, SeppoHämäläinen, Matti S.de Gelder, Beatrice M.L.2013-01-172008Meeren, Hanneke K. M., Nouchine Hadjikhani, Seppo P. Ahlfors, Matti S. Hämäläinen, and Beatrice de Gelder. 2008. Early category-specific cortical activation revealed by visual stimulus inversion. PLoS ONE 3(10): e3503.1932-6203http://nrs.harvard.edu/urn-3:HUL.InstRepos:10196736Visual categorization may already start within the first 100-ms after stimulus onset, in contrast with the long-held view that during this early stage all complex stimuli are processed equally and that category-specific cortical activation occurs only at later stages. The neural basis of this proposed early stage of high-level analysis is however poorly understood. To address this question we used magnetoencephalography and anatomically-constrained distributed source modeling to monitor brain activity with millisecond-resolution while subjects performed an orientation task on the upright and upside-down presented images of three different stimulus categories: faces, houses and bodies. Significant inversion effects were found for all three stimulus categories between 70–100-ms after picture onset with a highly category-specific cortical distribution. Differential responses between upright and inverted faces were found in well-established face-selective areas of the inferior occipital cortex and right fusiform gyrus. In addition, early category-specific inversion effects were found well beyond visual areas. Our results provide the first direct evidence that category-specific processing in high-level category-sensitive cortical areas already takes place within the first 100-ms of visual processing, significantly earlier than previously thought, and suggests the existence of fast category-specific neocortical routes in the human brain.en-USneurosciencecognitive neurosciencesensory systemsexperimental psychologynatural and synthetic visionJournal Article2013-01-1710.1371/journal.pone.0003503