title: A contrast and surface code explains complex responses to black and white stimuli in V1.
abstract: We investigated the cortical mechanisms underlying the visual perception of luminance-defined surfaces and the preference for black over white stimuli in the macaque primary visual cortex, V1. We measured V1 population responses with voltage-sensitive dye imaging in fixating monkeys that were presented with white or black squares of equal contrast around a mid-gray. Regions corresponding to the squares' edges exhibited higher activity than those corresponding to the center. Responses to black were higher than to white, surprisingly to a much greater extent in the representation of the square's center. Additionally, the square-evoked activation patterns exhibited spatial modulations along the edges and corners. A model comprised of neural mechanisms that compute local contrast, local luminance temporal modulations in the black and white directions, and cortical center-surround interactions, could explain the observed population activity patterns in detail. The model captured the weaker contribution of V1 neurons that respond to positive (white) and negative (black) luminance surfaces, and the stronger contribution of V1 neurons that respond to edge contrast. Also, the model demonstrated how the response preference for black could be explained in terms of stronger surface-related activation to negative luminance modulation. The spatial modulations along the edges were accounted for by surround suppression. Overall the results reveal the relative strength of edge contrast and surface signals in the V1 response to visual objects.
authors.affiliation: The Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, 52900 Ramat Gan, Israel and.
authors.forename: Guy
authors.initials: G
authors.lastname: Zurawel
authors.affiliation: The Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, 52900 Ramat Gan, Israel and.
authors.forename: Inbal
authors.initials: I
authors.lastname: Ayzenshtat
authors.affiliation: The Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, 52900 Ramat Gan, Israel and.
authors.forename: Shay
authors.initials: S
authors.lastname: Zweig
authors.affiliation: Center for Neural Science, New York University, New York, New York 10003.
authors.forename: Robert
authors.initials: R
authors.lastname: Shapley
authors.affiliation: The Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, 52900 Ramat Gan, Israel and Hamutal.Slovin@biu.ac.il.
authors.forename: Hamutal
authors.initials: H
authors.lastname: Slovin
mesh_terms: D000818:Animals; D015350:Contrast Sensitivity / Q000502:physiology*; D008252:Macaca fascicularis; D008297:Male; D010775:Photic Stimulation / Q000379:methods*; D011597:Psychomotor Performance / Q000502:physiology*; D011897:Random Allocation; D011930:Reaction Time / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology
keywords: black response; monkey; primary visual cortex; surface; voltage-sensitive dye imaging; white response