Cardiff University | Prifysgol Caerdydd ORCA
Online Research @ Cardiff 
WelshClear Cookie - decide language by browser settings

Surround modulation measured with functional MRI in the human visual cortex

Williams, A. L., Singh, Krish Devi and Smith, A. T. 2003. Surround modulation measured with functional MRI in the human visual cortex. Journal of Neurophysiology 89 (1) , pp. 525-533. 10.1152/jn.00048.2002

Full text not available from this repository.


Visual context profoundly influences 1) the responses of mammalian visual neurons and 2) the perceptual sensitivity of human observers to localized visual stimuli. We present data from functional MRI studies demonstrating contextual modulation in the human visual cortex. Subjects viewed a circular grating patch that was continuously present. A surround grating was added in an ON-OFF block design to reveal its effect on the central region. Stimulus-correlated activation was quantified and visualized on a flattened map of the occipital gray matter. Modulation was measured in a region of interest activated by the central grating alone. The observed effects were predominantly suppressive, consistent with the effects typically found in single neurons and perception. Suppression was greatest when the surround and center had the same orientation and was reduced or absent when it was orthogonal. When spatial phase was manipulated, suppression was greatest for in-phase center/surround gratings and much reduced or reversed (facilitation) for opposite-phase stimuli. With eccentric stimulus presentation, suppression was reduced and facilitation became more common. The findings provide a direct demonstration of the existence of powerful and stimulus-specific surround effects in human visual cortex.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Psychology
Neuroscience and Mental Health Research Institute (NMHRI)
Subjects: B Philosophy. Psychology. Religion > BF Psychology
R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
Publisher: American Physiological Society
ISSN: 0022-3077
Last Modified: 04 Jun 2017 04:10

Citation Data

Cited 59 times in Google Scholar. View in Google Scholar

Cited 65 times in Scopus. View in Scopus. Powered By Scopus® Data

Actions (repository staff only)

Edit Item Edit Item