Journal of Neuroscience, Vol 14, 929-948, Copyright © 1994 by Society for Neuroscience
Two stages in visual texture segregation: a lesion study in the cat
P De Weerd, JM Sprague, E Vandenbussche and GA Orban
Laboratorium voor Neuro- en Psychofysiologie, Katholieke Universiteit te Leuven, Belgium.
We have used five cats to investigate the effects of two distinct visual
cortex lesions on the segregation of two different texture stimuli. The
ablation of areas 17 and 18 (tier I) severely impaired the segregation
between textures made of line elements differing in orientation, but spared
the segregation between annulus and dot textures. In contrast, the ablation
of those areas receiving direct afferents from areas 17 and 18 (tier II)
destroyed the segregation for both texture stimuli. Strong deficits
remained up to 1 year after the lesion, although limited recovery was
observed after tier II lesions. We suggest that tier I areas are involved
in the local filtering of the texture elements, and that tier II areas
compute texture differences on the basis of the filtered image provided by
tier I areas. The crucial contribution to texture segregation of visual
areas belonging to a second level in the cortical hierarchy challenges the
notion that texture segregation is entirely an early process in vision.