Neural Mechanism of Figure-Ground Segregation at Occluding Contours in Monkey Prestriate Cortex

Baumann, R.; Sauvan, Xavier M.; Peterhans, E.

doi:10.1016/b978-044482046-4/50048-1

Cited by 3 publications

(1 citation statement)

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“…The results suggest that mechanisms defining occluding contours and the direction of figure and ground at such contours are implemented early in visual processing, in the monkey at least at the level of prestriate cortex. Preliminary results have been reported at meetings (Peterhans and von der Heydt, 1992;von der Heydt et al, 1993;Baumann et al, 1996).…”

Section: Introductionmentioning

confidence: 96%

Figure‐Ground Segregation at Contours: a Neural Mechanism in the Visual Cortex of the Alert Monkey

Baumann

Zwan

Peterhans

1997

Eur J of Neuroscience

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An important task of vision is the segregation of figure and ground in situations of spatial occlusion. Psychophysical evidence suggests that the depth order at contours is defined early in visual processing. We have analysed this process in the visual cortex of the alert monkey. The animals were trained on a visual fixation task which reinforced foveal viewing. During periods of active visual fixation, we recorded the responses of single neurons in striate and prestriate cortex (areas V1, V2, and V3/V3A). The stimuli mimicked situations of spatial occlusion, usually a uniform light (or dark) rectangle overlaying a grating texture of opposite contrast. The direction of figure and ground at the borders of these rectangles was defined by the direction of the terminating grating lines (occlusion cues). Neuronal responses were analysed with respect to figure-ground direction and contrast polarity at such contours. Striate neurons often failed to respond to such stimuli, or were selective for contrast polarity; others were non-selective. Some neurons preferred a certain combination of figure-ground direction and contrast polarity. These neurons were rare both in striate and prestriate cortex. The majority of neurons signalled figure-ground direction independent of contrast polarity. These neurons were only found in prestriate cortex. We explain these responses in terms of a model which also explains neuronal signals of illusory contours. These results suggest that occlusion cues are used at an early level of processing to segregate figure and ground at contours.

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Section: Introductionmentioning

confidence: 96%