title: Unfamiliar Walking Movements Are Detected Early in the Visual Stream: An fMRI Study.
abstract: Two experiments investigated the network involved in the visual perception of walking. Video clips of forward and backward walk (real walk direction) were shown either as recorded, or reversed in time (rendering). In Experiment 1 (identification task), participants were asked to indicate whether or not the stimulus was time-reversed. In Experiment 2 (free-viewing), participants viewed the video clips passively. Identification accuracy was good with the more familiar scene, that is, when the visual walk was in the direction of the facing orientation, and at chance level in the opposite case. In both experiments, the temporo-occipital junction (TOJ) was activated more strongly by unfamiliar than familiar scenes. Only in Experiment 1 intraparietal, superior temporal, and inferior temporal regions were also activated. TOJ activation signals the detection in unfamiliar scenes of a mismatch between facing orientation and visual movement direction. We argue that TOJ response to a mismatch prevents the further processing of the visual input required to identify temporal inversions. When no mismatch is detected (familiar stimuli), TOJ would, instead, be involved in the kinematic analysis that makes such identification possible. The study demonstrates that unfamiliar walking movements are detected earlier than so far assumed along the visual movement processing stream.
authors: Laboratory of Neuromotor Physiology.
authors: Vincenzo
authors: V
authors: Maffei
authors: Laboratory of Neuromotor Physiology Centre of Space BioMedicine.
authors: Maria Assunta
authors: MA
authors: Giusti
authors: Laboratory of Neuroimaging, IRCCS Santa Lucia Foundation, 00179 Rome, Italy.
authors: Emiliano
authors: E
authors: Macaluso
authors: Laboratory of Neuromotor Physiology Centre of Space BioMedicine Department of Systems Medicine, University of Rome Tor Vergata, 00133 Rome, Italy.
authors: Francesco
authors: F
authors: Lacquaniti
authors: Laboratory of Neuromotor Physiology Centre of Space BioMedicine.
authors: Paolo
authors: P
authors: Viviani
mesh_terms: D000328:Adult; D001931:Brain Mapping; D053483:Eye Movement Measurements; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D021641:Recognition, Psychology / Q000502:physiology; D017603:Signal Detection, Psychological / Q000502:physiology; D014741:Video Recording; D014795:Visual Pathways / Q000502:physiology*; D016138:Walking; D055815:Young Adult
keywords: action observation; biological motion; fMRI; predictive coding