Andreas Bartels: Parietal function in ego-motion, space and Gestalt perception

Human parietal cortex consists of a number of distinct regions, some of which can be delineated from each other using retinotopic mapping. However, relatively little is known about their function in the healthy human brain. From primate physiology and clinical studies we know that they play crucial roles in coordinate transformations between eye-, head-, and body-centred space, in perceptual selection and visual grouping. I will present a series of fMRI studies (some combined with transcranial magnetic stimulation (TMS)) that shed light onto their roles. First, I will present occipito-parietal regions that encode visual object- and ego-motion cues when humans view natural movies. Second, I will show motion regions encoding motion in head- or world-centred coordinates, and whose additional properties suggest that they support processing of object-motion, of self-motion in 2D and in 3D, respectively. Third, I will show first evidence in the human brain for encoding of space beyond the visual field in egocentric coordinates, providing potential insights into function underlying deficits such as ataxia and neglect. Fourth, I will provide evidence for a causal role of parietal cortex in grouping, Gestalt perception and perceptual selection. If time permits, I may additionally show evidence in context of colour vision, demonstrating that early visual processing is heavily influenced by high-level expectations that are explicitly fed back to early visual cortex, which can be understood in context of predictive coding.