title: Two distinct mechanisms of suppression in human vision.
abstract: Cortical visual neurons in the cat and monkey are inhibited by stimuli surrounding their receptive fields (surround suppression) or presented within their receptive fields (cross-orientation or overlay suppression). We show that human contrast sensitivity is similarly affected by two distinct suppression mechanisms. In agreement with the animal studies, human surround suppression is tightly tuned to the orientation and spatial frequency of the test, unlike overlay suppression. Using a double-masking paradigm, we also show that in humans, overlay suppression precedes surround suppression in the processing sequence. Surprisingly, we find that, unlike overlay suppression, surround suppression is only strong in the periphery (> 1 degree eccentricity). This result argues for a new functional distinction between foveal and peripheral operations.
authors.affiliation: The Smith-Kettlewell Eye Research Institute, San Francisco, California 94115, USA. yury@ski.org
authors.forename: Yury
authors.initials: Y
authors.lastname: Petrov
authors.forename: Matteo
authors.initials: M
authors.lastname: Carandini
authors.forename: Suzanne
authors.initials: S
authors.lastname: McKee
mesh_terms: D000221:Adaptation, Ocular / Q000502:physiology; D015350:Contrast Sensitivity / Q000502:physiology*; D006801:Humans; D010775:Photic Stimulation / Q000379:methods*; D013028:Space Perception / Q000502:physiology*; D014785:Vision, Ocular / Q000502:physiology*