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Michiteru Kitazaki, Jun'ichi Katayama, Nobuko Komori, Shoji Itakura; Development of visual control of posture in sensitivity function of motion frequency. Journal of Vision 2007;7(9):1025. doi: 10.1167/7.9.1025.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Optical flow is utilized to control posture for infants as well as adults (Lee and Aronson, 1974). It is reported that infants' postural sway is induced by visual motion in a broad range of motion frequency (0.2–0.54Hz, Delorme, Frigon and Lagace, 1989; Schmuckler, 1997), but adults showed postural sway only for low-frequency motion ([[lt]]0.3Hz, van Asten, Gielen and van der Gon, 1988). We aimed to investigate developmental change of visual control of posture in function of motion frequency.
Method: Thirty-nine children (5–15 years old) and ten adults (20–28 years old) participated. Linear viewpoint motions in a cloud of dots were simulated in lateral (leftward and rightward) or in sagittal (forward and backward) direction, and cyclic back and forth at 0.1–0.6Hz. Participants' posture was measured at 60Hz by a force plate during observing the stimulus on an 80inch screen at 100cm distance. We analyzed the postural-sway data using Fourier transformation and extracted the power of sway synchronized to the visual motion.
Results: Total power of postural sway decreased as the observer getting elder. Individual difference was very large when adults observed lateral motion. Young children showed stronger postural sway at 0.6Hz than the lower frequency, but it was opposite for adults, who were more sensitive to 0.1–0.2Hz than 0.6Hz. The effective/sensitive frequency was shifted to lower frequency as the observer getting elder.
Discussion: These results suggested that the process for visual control of posture develops in childhood and its sensitivity function of motion frequency gradually changes. Shift of sensitive frequency to the lower frequency indicates the inhibition of high-frequency motion. Since optical flow on the retina must be decomposed and interpreted as object motion and self-motion, and the high-frequency motion would often correspond to object motion, the developmental shift of sensitivity function in our finding is ecologically reasonable.
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