The Human Brain in Depth: How We See in 3D

Abstract

Human perception is remarkably flexible: We experience vivid three-dimensional (3D) structure under diverse conditions, from the seemingly random magic-eye stereograms to the aesthetically beautiful, but obviously flat, canvases of the Old Masters. How does the brain achieve this apparently effortless robustness? Using brain imaging we are beginning to discover how different parts of the visual cortex support 3D perception by tracing different computations in the dorsal and ventral pathways. This review concentrates on studies of binocular disparity and its combination with other depth cues. This work suggests that the dorsal visual cortex is strongly engaged by 3D information and is involved in integrating signals to represent the structure of viewed surfaces. The ventral cortex may store representations of object configurations and the features required for task performance. These differences can be broadly understood in terms of the different computational demands of reducing estimator variance versus increasing the separation between exemplars.

Specialization of mid-tier stages of dorsal and ventral pathways in stereoscopic processing

“…As a precise cue for stereoscopic depth, binocular disparity is used for many functions, including the recognition of 3D objects, visually guided 3D action (e.g., reaching, grasping, and vergence eye movement), and navigation through the 3D environment (e.g., moving through obstacles). As binocular disparity is used for both "what" (object vision) and "where" (spatial vision) functions, the visual system processes binocular disparity along both the dorsal and ventral pathways (Neri, 2005;Orban et al, 2006;Parker, 2007;Roe et al, 2012;Welchman, 2016).…”

Modality-independent effect of gravity in shaping the internal representation of 3D space

“…Given its importance for interacting with the physical world, 3D object perception has been deeply investigated. Visual perception has received the most attention, showing how various features of the stimuli as disparities, size, occlusions, perspective, motion, shadows, shading, texture and blur all influence 3D visual perception (Welchman 2016) and how internal models constraint/shape the interpretation of the sensory signals (Curry 1972, Kersten and Yuille 2003, Kersten et al 2004, Lee 2015. Despite its critical importance to perception and action, visual perception suffers from measurable distortions: height underestimation with respect to width, also known as the horizontal-vertical, or "L", illusion (Avery andDay 1969, Hamburger andHansen 2010) and a systematic depth underestimation Philbeck 1999, Todd andNorman 2003).…”

Dissociating neural activity associated with the subjective phenomenology of monocular stereopsis: an EEG study

“…Methodologically, we localized EEG oscillatory sources (beamformer techniques) in the visual and parietal cortex, and conducted time-frequency analysis to examine power change in alpha (8-13Hz) and gamma (60-90Hz) frequency in both regions. We anticipated that the dissociable neural activity associated with depth perception would be most likely identified in gamma frequency band based on previous literature that 3D processing is largely a stimulus driven bottom-up process (Cumming and DeAngelis, 2001; Gonzalez and Perez, 1998; Orban, 2011; Parker, 2007; Welchman, 2016; Welchman and Kourtzi, 2013).…”