title: Visual and Haptic Shape Processing in the Human Brain: Unisensory Processing, Multisensory Convergence, and Top-Down Influences.
abstract: Humans are highly adept at multisensory processing of object shape in both vision and touch. Previous studies have mostly focused on where visually perceived object-shape information can be decoded, with haptic shape processing receiving less attention. Here, we investigate visuo-haptic shape processing in the human brain using multivoxel correlation analyses. Importantly, we use tangible, parametrically defined novel objects as stimuli. Two groups of participants first performed either a visual or haptic similarity-judgment task. The resulting perceptual object-shape spaces were highly similar and matched the physical parameter space. In a subsequent fMRI experiment, objects were first compared within the learned modality and then in the other modality in a one-back task. When correlating neural similarity spaces with perceptual spaces, visually perceived shape was decoded well in the occipital lobe along with the ventral pathway, whereas haptically perceived shape information was mainly found in the parietal lobe, including frontal cortex. Interestingly, ventrolateral occipito-temporal cortex decoded shape in both modalities, highlighting this as an area capable of detailed visuo-haptic shape processing. Finally, we found haptic shape representations in early visual cortex (in the absence of visual input), when participants switched from visual to haptic exploration, suggesting top-down involvement of visual imagery on haptic shape processing.
authors.affiliation: Department of Brain and Cognitive Engineering, Korea University, Seoul 136-713, Korea.
authors.forename: Haemy
authors.initials: H
authors.lastname: Lee Masson
authors.affiliation: Laboratory of Biological Psychology, KU Leuven, Leuven 3000, Belgium.
authors.forename: Jessica
authors.initials: J
authors.lastname: Bulthé
authors.affiliation: Laboratory of Biological Psychology, KU Leuven, Leuven 3000, Belgium.
authors.forename: Hans P
authors.initials: HP
authors.lastname: Op de Beeck
authors.affiliation: Department of Brain and Cognitive Engineering, Korea University, Seoul 136-713, Korea.
authors.forename: Christian
authors.initials: C
authors.lastname: Wallraven
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging / Q000502:physiology*; D001931:Brain Mapping; D005260:Female; D006801:Humans; D007600:Judgment / Q000502:physiology; D007858:Learning / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008297:Male; D009434:Neural Pathways / Q000000981:diagnostic imaging / Q000502:physiology; D009483:Neuropsychological Tests; D011897:Random Allocation; D055698:Touch Perception / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: haptics; multisensory; multivoxel analysis; shape perception