Integration of texture and disparity cues to 1 surface slant in dorsal visual cortex . 2 3

26 Reliable estimation of 3D surface orientation is critical for recognizing and interacting with 27 complex 3D objects in our environment. Human observers maximize the reliability of their 28 estimates of surface slant by integrating multiple depth cues. Texture and binocular disparity 29 are two such cues, but they are qualitatively very different. Existing evidence suggests 30 representations of surface tilt from each of these cues coincide at the single neuron level in 31 higher cortical areas. However, the cortical circuits responsible for 1) integration of such 32 qualitatively distinct cues, and 2) encoding the slant component of surface orientation, have 33 not been assessed. We tested for cortical responses related to slanted plane stimuli that 34 were defined independently by texture, disparity, and combinations of these two cues. We 35 analysed the discriminability of functional MRI responses to two slant angles using 36 multivariate pattern classification. Responses in visual area V3B/KO to stimuli containing 37 congruent cues were more discriminable than those elicited by single cues, in line with 38 predictions based on the fusion of slant estimates from component cues. This improvement 39 was specific to congruent combinations of cues: incongruent cues yielded lower decoding 40 accuracies, which suggests the robust use of individual cues in cases of large cue conflicts. 41 These data suggest that area V3B/KO is intricately involved in the integration of qualitatively 42 dissimilar depth cues. 43 44