Neural Correlates for Perception of 3D Surface Orientation from Texture Gradient
and spread throughout the cell as the worm moved. In contrast, mitochondria in anc-1(e1873) animals were spherically shaped, often clustered together, and were pushed around within the cytoplasm as the animal moved ( Fig. 4B ). Mitochondria were not shaped or positioned properly in an unc-60(r398) mutant background (Fig. 4D) . A partial loss-of-function allele in the C. elegans cofilin homolog, unc-60(r398), disrupts actin filaments in the body wall muscle of adult hermaphrodites (23).
... , actin filaments are required for proper positioning of mitochondria. The anchorage of mitochondria in unc-84(n369) was normal (Fig. 4C ), suggesting that ANC-1 does not require UNC-84 to anchor mitochondria as it does for nuclear anchorage. Our model ( fig. S4 ) suggests that ANC-1 functions to anchor nuclei by tethering the nucleus to the actin cytoskeleton and predicts that the KASH domain of ANC-1 is localized to the outer nuclear envelope by UNC-84. Digitonin extraction experiments show that human Syne-2 localizes to the outer nuclear envelope (14) . ANC-1 would then extend away from the nucleus, where its NH 2 -terminus binds to the stable actin cytoskeleton. As a result, ANC-1 molecules function to directly attach the actin cytoskeleton to the nuclear envelope. Before a nucleus can migrate through the cytoplasm of the cell, the nuclear anchor must be released. The SUN domain of UNC-84 is likely to be intimately involved with this switch in nuclear behavior, because it is required for both ANC-1 and UNC-83 localization at the nuclear envelope (21) (Fig. 2) . UNC-83 is required for normal nuclear migration but not for nuclear anchorage (21). It is not known whether ANC-1 and UNC-83 can interact with UNC-84 simultaneously, although both antigens are detected at the nuclear envelope of adult hypodermal cells. Overexpression of UNC-83 did not cause any obvious anchorage phenotype, eliminating a competition model. Dystrophin and the associated dystrophin-glycoprotein complex function to connect the actin cytoskeleton to the extracellular matrix; mutations in these components lead to Duchenne or Becker muscular dystrophies (24). Although ANC-1 and Syne connect the actin cytoskeleton to the nuclear matrix whereas dystrophin connects actin to the extracellular matrix, there are some similarities between these two mechanisms. ANC-1 and associated proteins, including UNC-84 and lamin A/C (12), are likely to create a bridge across the nuclear envelope. Mutations in the gene encoding lamin A/C lead to Emery-Dreifuss muscular dystrophy (24), which suggests a potential link between the ANC-1 and Syne proteins and muscular dystrophy. A goal in visual neuroscience is to reveal how the visual system reconstructs the three-dimensional (3D) representation of the world from two-dimensional retinal images. Although the importance of texture gradient cues in the process of 3D vision has been pointed out, most studies concentrate on the neural process based on binocular disparity. We report the neural correlates of depth perception from texture gradient in the cortex. In the caudal part of the lateral bank of intraparietal sulcus, many neurons were selective to 3D surface orientation defined by texture gradient, and their response was invariant over different types of texture pattern. Most of these neurons were also sensitive to a disparity gradient, suggesting that they integrate texture and disparity gradient signals to construct a generalized representation of 3D surface orientation.