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Melissa M. Kibbe, Sung-Ho Kim, Steven Cholewiak, Kristina Denisova; Curvature aftereffect and visual-haptic interactions in simulated environments. Journal of Vision 2011;11(11):784. doi: 10.1167/11.11.784.
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© 2016 Association for Research in Vision and Ophthalmology.
Repeated haptic exploration of a surface with curvature results in an adaptation effect, such that flat surfaces feel curved in the opposite direction of the explored surface. Previous studies used real objects and involved contact of skin on surface with no visual feedback. To what extent do cutaneous, proprioceptive, and visual cues play a role in the neural representation of surface curvature? The current study used a Personal Haptic Interface Mechanism (PHANToM) force-feedback device to simulate physical objects that subjects could explore with a stylus. If haptic aftereffect is observed in exploration of virtual surfaces, it suggests neural representations of curvature based solely on proprioceptive input. If visual input plays a role in the absence of haptic convexity/concavity, it would provide evidence for a visual input to the neural haptic representation. Method. Baseline curvature discrimination was obtained from subjects who explored a virtual surface with the stylus and reported whether it was concave or convex. In Experiment 1, subjects adapted to a concave or convex curvature (±3.2 m−1) and reported the curvature of a test surface (ranging from −1.6 m−1 to 1.6 m−1). In Experiment 2, subjects adapted with their left hands and tested with their right (intermanually). In Experiment 3, subjects were given visual feedback on a computer screen that the trajectory of the stylus tip was a curved surface, while the haptic surface was flat. Results. In Experiment 1, subjects showed a strong curvature aftereffect, indicating that proprioceptive input alone is sufficient. Subjects in Experiment 2 showed weaker but significant adaptation, indicating a robust neural representation across hands. No aftereffect was found with solely visual curvature input in Experiment 3, suggesting that the neural representation is not affected by synchronized visual feedback, at least when two modalities do not agree. Implications for visual-haptic representations will be discussed.
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