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Adria Hoover, Laurence Harris; Varying the visual perspective in which head and finger movement is seen affects cross-modal synchrony detection. Journal of Vision 2012;12(9):1315. doi: https://doi.org/10.1167/12.9.1315.
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Temporal congruency between different sources of information concerning a self-made movement provides a strong cue for self-identification. Activity in visual body areas in the brain is correlated with self-made movement, implying interconnectivity between visual and proprioceptive information in the representation of the body. We hypothesized that when the viewpoint from which a movement is viewed matches the internal representation, it may result in greater sensitivity to detect a delay between a movement and visual feedback. We therefore looked for variation in this sensitivity with viewpoint to clarify the organization of the visual representation of the body. We measured the threshold and sensitivity (d’) for detecting a delay between self-generated movement of the finger or head and visual feedback from various perspectives. For the hand, we compared the natural view with the mirror-reversed and/or inverted view. For the head, the "natural view" was as seen in a mirror. For the back-of-the-head, the "natural view" was from behind the subject. We used a 2AFC paradigm where each trial consisted of one period with a minimum delay and another with a delay of between 1 and 8 video frames (33 ms/frame). Subjects indicated which period contained the delayed view. Sensitivity to detect asynchrony between visual and proprioceptive information was significantly higher when movements were viewed from the "natural view" perspective compared to when the view was reversed or inverted. Further, detection of asynchrony was more sensitive for movements of body parts that are seen most often (hands) than for body parts that are seen only indirectly (face-in-a-mirror) or that are never seen at all (back-of-the-head). Variations in sensitivity to visual/non-visual temporal incongruence with the viewpoint in which a movement is seen may help determine the arrangement of the underlying visual representation of the body.
Meeting abstract presented at VSS 2012
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