Occipital network for figure/ground organization |
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Authors: | Lora T Likova Christopher W Tyler |
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Institution: | (1) The Smith-Kettlewell Eye Research Institute, San Francisco, CA, USA |
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Abstract: | To study the cortical mechanism of figure/ground categorization in the human brain, we employed fMRI and the temporal-asynchrony
paradigm. This paradigm is able to eliminate any differential activation for local stimulus features, and thus to identify
only global perceptual interactions. Strong segmentation of the image into different spatial configurations was generated
solely from temporal asynchronies between zones of homogeneous dynamic noise. The figure/ground configuration was a single
geometric figure enclosed in a larger surround region. In a control condition, the figure/ground organization was eliminated
by segmenting the noise field into many identical temporal-asynchrony stripes. The manipulation of the type of perceptual
organization triggered dramatic reorganization in the cortical activation pattern. The figure/ground configuration generated
suppression of the ground representation (limited to early retinotopic visual cortex, V1 and V2) and strong activation in
the motion complex hMT+/V5+; conversely, both responses were abolished when the figure/ground organization was eliminated.
These results suggest that figure/ground processing is mediated by top-down suppression of the ground representation in the
earliest visual areas V1/V2 through a signal arising in the motion complex. We propose a model of a recurrent cortical architecture
incorporating suppressive feedback that operates in a topographic manner, forming a figure/ground categorization network distinct
from that for “pure” scene segmentation and thus underlying the perceptual organization of dynamic scenes into cognitively
relevant components.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Perceptual organization Figure/ground Contextual interactions Temporal asynchrony Visual cortex Suppression Salience Top-down feedback V1 V2 hMT+ |
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