Occipital network for figure/ground organization

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 diferential activation for local

stimulus features, and thus to identify only global perceptual

interactions. Strong segmentation of the image into

diferent 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 topdown

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.