The integration of motion and disparity cues to depth in dorsal visual cortex

Humans exploit a range of visual depth cues to estimate three-dimensional (3D) structure. For example, the slant of a nearby tabletop can be judged by combining information from binocular disparity, texture and perspective. Behavioral tests show humans combine cues near-optimally, a feat that could depend on: (i) discriminating the outputs from cue-specific mechanisms, or (ii) fusing signals into a common representation. While fusion is computationally attractive, it poses a significant challenge, requiring the integration of quantitatively different signals. We used functional magnetic resonance imaging (fMRI) to provide evidence that dorsal visual area V3B/KO meets this challenge. Specifically, we found that fMRI responses are more discriminable when two cues (binocular disparity and relative motion) concurrently signal depth, and that information provided by one cue is diagnostic of depth indicated by the other. This suggests a cortical node important when perceiving depth, and highlights computations based on fusion in the dorsal stream.