title: Contour extracting networks in early extrastriate cortex.
abstract: Neurons in the visual cortex process a local region of visual space, but in order to adequately analyze natural images, neurons need to interact. The notion of an ‘‘association field’’ proposes that neurons interact to extract extended contours. Here, we identify the site and properties of contour integration mechanisms. We used functional magnetic resonance imaging (fMRI) and population receptive field (pRF) analyses. We devised pRF mapping stimuli consisting of contours. We isolated the contribution of contour integration mechanisms to the pRF by manipulating the contour content. This stimulus manipulation led to systematic changes in pRF size. Whereas a bank of Gabor filters quantitatively explains pRF size changes in V1, only V2/V3 pRF sizes match the predictions of the association field. pRF size changes in later visual field maps, hV4, LO-1, and LO-2 do not follow either prediction and are probably driven by distinct classical receptive field properties or other extraclassical integration mechanisms. These pRF changes do not follow conventional fMRI signal strength measures. Therefore, analyses of pRF changes provide a novel computational neuroimaging approach to investigating neural interactions. We interpreted these results as evidence for neural interactions along cooriented, cocircular receptive fields in the early extrastriate visual cortex (V2/V3), consistent with the notion of a contour association field.
authors.affiliation: Department of Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, Netherlands.
authors.forename: Serge O
authors.initials: SO
authors.lastname: Dumoulin
authors.affiliation: McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Canada.
authors.forename: Robert F
authors.initials: RF
authors.lastname: Hess
authors.affiliation: Division of Optometry and Visual Science, City University London, London, UK.
authors.forename: Keith A
authors.initials: KA
authors.lastname: May
authors.affiliation: Department of Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, Netherlands.
authors.forename: Ben M
authors.initials: BM
authors.lastname: Harvey
authors.affiliation: Department of Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, NetherlandsDepartment of Psychology, University of Wisconsin-Madison, Madison, WI, USA.
authors.forename: Bas
authors.initials: B
authors.lastname: Rokers
authors.affiliation: Department of Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, NetherlandsDepartment of Psychology, University of Wisconsin-Madison, Madison, WI, USA.
authors.forename: Martijn
authors.initials: M
authors.lastname: Barendregt
mesh_terms: D000328:Adult; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009474:Neurons / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology*; D055815:Young Adult
keywords: Gabor filter; association field; functional magnetic resonance imaging; population receptive fields; visual cortex