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Anastasia Flevaris, Scott Murray; Grouping-based attention influences surround suppression in human primary visual cortex. Journal of Vision 2014;14(10):802. doi: 10.1167/14.10.802.
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© ARVO (1962-2015); The Authors (2016-present)
Surround suppression is a form of contextual modulation in V1 in which the response to a stimulus inside the receptive field of a neuron is reduced when it is surrounded by stimuli just outside of the receptive field. The suppression is greatest when the surrounding stimuli share the same low-level features such as orientation and spatial frequency. In contrast, previous studies of perceptual grouping have shown that attending to one element in a group automatically spreads to other members of the group, thereby increasing the neural response to similar features. A key difference between findings of grouping-based suppression versus enhancement is directed attention. Investigations of surround suppression have predominately examined suppression to unattended elements, and the few studies investigating attentional influences on surround suppression have used displays in which grouping could not be explicitly examined. Here, we asked if both effects could be seen in the same paradigm by using three-element displays that could be perceptually grouped and manipulating the direction of attention. The displays consisted of a center oriented Gabor and two flanking Gabors positioned above and below the center. The center and surrounding Gabors either had the same or orthogonal orientation, and attention was directed either to the center element or to the upper (surrounding) element. Using fMRI, we measured the V1 response to the center element when it had the same orientation as the surrounding flankers versus when the orientations differed. When attention was directed to the center element itself, we found evidence of surround suppression; the V1 response to the center element was reduced when the surrounding orientations were the same relative to when they were different. In contrast, when attention was directed to the upper element, grouping-based attentional spreading reversed this effect, demonstrating a high-level influence of grouping-based attention on surround suppression in V1.
Meeting abstract presented at VSS 2014
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