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Prism adaptation is a sensory-motor adaptation that occurs after the visual field has been artificially shifted laterally or vertically. It was first introduced by Hermann von Helmholtz in late 19th-century Germany as supportive evidence for his perceptual learning theory (Helmholtz, 1909/1962).〔Helmholtz, H. E. F. von (1909/1962). Treatise on Physiological Optics. J. P. C. Southall, Ed. and Trans. New York: Dover. (Original work published in 1909).〕 Since its discovery, prism adaptation has been suggested to improve spatial deficits in patients with unilateral neglect. ==Prism adaptation paradigm== During prism adaptation, an individual wears special prismatic goggles that are made of prism wedges that displace the visual field laterally or vertically. In most cases the visual field is shifted laterally either in the rightward or leftward direction. While wearing the goggles, the individual engages in a perceptual motor task such as pointing to a visual target directly in front of them. A prism adaptation session includes three components: the pre-test, prism exposure, and the post-test. The effects of the prism adaptation paradigm are observed when the performance on the perceptual motor task of the pre-and post-test are compared. # ''Pre-test'': For example, the pre-test measures the observer's ability to point to the visual target directly in front of them before prism exposure. This task can be completed with ease and accuracy by normal, healthy individuals. # ''Prism Exposure'': During prism exposure, the initial attempts at pointing to the target are off- target because the observer’s visual field has been laterally shifted in one direction. The initial pointing errors during prism exposure occur in the same direction of the visual shift. For example, if the prismatic goggles displace the visual field to the right, the initial pointing errors would occur to the right of the visual target until a sensory-motor adaptation known as the ‘direct effect of prism adaptation’ occurs. The initial pointing errors induced by the prismatic goggles are caused by the misalignment of the observer’s motor and proprioceptive maps. Once the error has been detected, the observer makes a conscious effort to try and fix the error via strategic recalibration. The reduction in error is also helped by an unconscious process referred to as spatial realignment, which gradually realigns the visual and proprioceptive maps (Newport and Schenk, 2012).〔Newport R, Schenk T (2012) Prisms and neglect: What have we learned? Neuropsychologia, 50 (6): 1080–1091. Pisella L, Rode G, Famè A, Boisson D, and Rossetti Y (2002) Dissociated long lasting improvements of straight ahead pointing and line bisection tasks in two hemineglect patients. Neuropsychologia, 40(3): 327–334, 2002.〕 This means that over a series of repeated attempts, the observer is able to reduce the margin of error and become more accurate in pointing to the visual target despite the visual displacement. Usually it takes an individual as few as 10 trials to adapt to the visual displacement and successfully point to the target (Rosetti et al., 1993). 3) ''Post-test'': During the post test the prismatic goggles are removed. The direct effect adaptation observed as a result of prism exposure persists and results in what is known as the prism adaptation negative after-effect. The negative after-effect causes the initial attempts in pointing to the visual target during the post-test to be in the direction opposite that of the visual shift. For example, if the observer was exposed to rightward shifting prisms, then the initial pointing errors induced by the after-effect would be to the left of the target. The extent of the observed after-effects reflects the amount of realignment that has taken place in visual and proprioceptive spatial maps during prism exposure (Newport and Schnek, 2012). The negative after-effect is not permanent but varies in its duration depending on the amount of sessions and time the patient is exposed to prism adaptation sessions. Eventually the after-effect wears off and pointing abilities return to pre-test levels. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Prism adaptation」の詳細全文を読む スポンサード リンク
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