Unfamiliar Walking Movements Are Detected Early in the Visual Stream: An fMRI Study

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...

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Bibliographic Details
Published in:Cerebral cortex (New York, N.Y. 1991) N.Y. 1991), 2015-08, Vol.25 (8), p.2022-2034
Main Authors: Maffei, Vincenzo, Giusti, Maria Assunta, Macaluso, Emiliano, Lacquaniti, Francesco, Viviani, Paolo
Format: Article
Language:English
Subjects:
Adult
Brain Mapping
Eye Movement Measurements
Female
Humans
Magnetic Resonance Imaging
Male
Motion Perception - physiology
Pattern Recognition, Visual - physiology
Photic Stimulation
Recognition (Psychology) - physiology
Signal Detection, Psychological - physiology
Visual Pathways - physiology
Walking
Young Adult
Online Access:Get full text
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Summary: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.
ISSN:1047-3211
1460-2199
DOI:10.1093/cercor/bhu008