背景與目的：本研究探討適應視覺上動作幅度的橫向分量改變是否會影響動作幅度的縱向分量的控制，以及適應視覺上動作幅度的縱向分量改變是否會影響動作幅度的橫向分量的控制，以進一步瞭解動作幅度的橫向與縱向分量是否能被獨立控制。

研究方法：本研究的對象為慣用手為右手的健康年輕人19 名，平均年齡23.6±3.1 歲，按照徵召順序分為兩組，分別適應視覺上動作幅度的橫向分量改變(GH)與動作幅度的縱向分量改變(GV)。受試者在手寫板上執行水平面上的點對點動作，動作距離12 公分，目標方向包括0 度、30 度、60 度和90 度，總共須完成480 個動作。適應過程包括適應前階段、漸進適應期、適應期和後適應期四個階段。在適應前階段時，動作的視覺動作關係同正常環境，在漸進適應期時，動作的橫向或縱向分量的視覺顯示率(視覺上看到的動作幅度/實際動作的動作幅度)會漸漸縮小至0.67，在適應期時視覺顯示率則一直維持在0.67，後適應期則同適應前階段。本實驗紀錄頭戴式顯示器和手寫板上的軌跡資料，分析參數包括動作固定誤差、適應速率和動作增加率。

研究結果：在適應期時，兩組受試者都能適應橫軸或縱軸視覺動作關係的縮小而放大動作幅度，在後適應期時，兩組都有產生明顯的固定誤差(GH：F1,8= 45.985，p<0.01；GV：F1,9=22.993，p<0.01)，但組間沒有顯著的差異(p= 0.811)。就動作增加率而言，在適應期動作幅度的橫向分量與縱向分量呈現明顯的差異(GH：F1,8=5382.709，p<0.01；GV：F1,9=1648.702，
p<0.01)，適應視覺上動作幅度在橫向分量改變的受試者表現出橫向分量的改變但縱向分量不變，適應縱向分量改變的受試者則表現出縱向分量的改變但橫向分量不變。在後適應期，兩組的動作誤差在動作幅度橫向分量與縱向分量之間也呈現明顯的差異(GH：F1,8=46.059，p<0.01；GV: F1,9= 54.995，p<0.01)，適應視覺上動作幅度在橫向分量改變的受試者表現出動作幅度在橫向分量的固定誤差相對於適應期時明顯增加，但縱向分量的固定誤差則沒有顯著的改變，適應視覺上動作幅度的縱向分量改變的受試者其動作幅度分量的固定誤差則是縱向分量有明顯改變但橫向分量則沒有明顯改變。此外，比較兩組在後適應期時的適應速率並沒有明顯的差異(p=0.838)。

結論：本研究結果顯示適應視覺上動作幅度的橫向分量改變，並不會影響動作幅度的縱向分量的控制，同樣的適應視覺上動作幅度的縱向分量改變，並不會影響動作幅度的橫向分量的控制。以上結果表示動作幅度的橫向與縱向分量可以被獨立控制。

Background and purposes: The aims of this study were to determine (1) whether the control of vertical component of the movement amplitude would be affected after adapting
to the change of visuomotor relationship in the horizontal component of the movement amplitude; and (2) whether the control of horizontal component of the movement amplitude would be affected after adapting to the change of visuomotor relationship in the vertical component of the movement amplitude. We expected to gain insight into the
question if the horizontal and vertical component in a planar movement could be control independently.

Methods: Nineteen right-handed healthy young adults were recruited and assigned to one of the following two groups: (1) adapting to the horizontal visual display gain change, and (2) adapting to the vertical visual display gain change. The task was to make a horizontal reaching movement to point to a target. The targets were located along 0°, 30°, 60° and 90° with respect to the horizontal axis. A total number of trials were 480 for 4 separate adaptation phases: pre-adaption phase, adjust-adaptation phase, adaption phase and post-adaption phase. During pre-adaptation phase, the visual display gain was 1. During adjust-adaptation phase, the visual display gain of movement’s horizontal or vertical component was decreased gradually from 1 to 0.67 and then remained as 0.67 for
the entire adaptation phase. The visual display gain in the post-adaptation phase was changed back to 1, same as in the pre-adaptation phase. The constant error, adaptation rate,
and movement amplitude gain was calculated from the recorded movement trajectory.

Results: During adaptation, the subjects of both groups showed adaptation to the gradually decreased visual display gain by enlarging the hand movement amplitude. Therefore, a
significant increase in constant error appeared at early post-adaptation phase compared to that at the pre-adaptation phase (GH: F1,8=45.985, p<0.01; GV: F1,9=22.993, p<0.01). However, no significant group difference was found (p=0.811). The horizontal component and vertical component of movement amplitude gain was significantly different during adaptation (GH: F1,8=5382.709, p<0.01; GV: F1,9= 1648.702, p<0.01). In the group adapting to the horizontal visual display gain changes, the horizontal component of movement amplitude gain changed significantly but the vertical component did not. In the group adapting to the vertical visual display gain change, the vertical component of movement amplitude gain changed significantly but the horizontal component of movement amplitude gain did not. During post-adaptation phase, both groups showed the significant difference between horizontal and vertical component of constant error (GH：F1,8=46.059，p<0.01；GV：F1,9=54.995，p<0.01). The group adapting to the horizontal visual display gain change showed a significant larger horizontal component of constant error relative to at the adaptation phase but the vertical component did not. In the group adapting to the vertical visual display gain change, the vertical component of constant error was significant larger at the post-adaptation phase compared to at the adaptation phase but the horizontal component did not. In terms of adaptation rate, the two groups had no significant difference at early stage of post-adaptation phas(p=0.838).

Conclusion: The results showed that adaptation to the horizontal display gain change did not affect the control of
vertical component of movement amplitude and adaptation to the vertical display gain change did not affect the control of the horizontal component of movement amplitude.

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