研究目的：動作學習是反覆練習造成動作表現的進步，有學者認為學習新動作會產生新的內部模型，當不同動作的內部模型間有較多交集，可產生更明顯的學習轉移；過去學者多觀察相似動作或是兩側肢體的學習轉移，較少針對簡單動作到複雜動作的學習轉移與學習轉移對視覺迴授的依賴進行探討；本實驗使用動作表現及伴隨動作震顫來觀察：學習簡單位移追蹤練習後，在複合位移追蹤動作的學習轉移效應，並探討視覺迴授在學習轉移過程中，對內部動作模型概化之影響。
研究方法：徵召十六位健康受試者，要求受試者的食指跟隨螢幕出現的正弦波形做交替內收及外展的動作，在提供視覺迴授的情形下，學習0.25Hz、0.75Hz兩種簡單正弦波位移追蹤動作，每次練習時間為40秒，中間間隔40秒作休息，每個項目練習8次，共16次，以雷射位移記錄系統，記錄學習前後0.25Hz、0.75Hz簡單正弦波位移追蹤動作、與有無視覺迴授下複合波追蹤動作等四種追蹤動作情況下，食指表現曲線與動作震顫資料，為防止疲勞影響數據，在學習後測驗結束15分鐘再施予相同的測驗。由學習前後的食指表現曲線與目標曲線，分析振幅耦合程度與表現總誤差值，並計算表現與相對進步量；動作震顫部份以均方根值代表振幅大小，進行功率頻譜密度分析去探討高峰頻率於學習後之變化。
研究結果：學習簡單位移追蹤動作後，複合正弦波追蹤動作表現曲線與目標曲線之耦合度顯著增加，且表現總誤差顯著減少，特別是有視覺迴授的複合正弦波其振幅耦合的相對進步量遠大於其他三項測驗；然而，複合正弦波表現總誤差值的進步量在有無視覺迴授下並沒有顯著不同；震顫分析部分的結果顯示：在頻率較高的0.75Hz與複合波追蹤測驗中，震顫振幅在學習後皆有顯著的變小，而0.75Hz及有視覺迴授複合波追蹤測驗震顫振幅相對改變量雖多於0.25Hz追蹤測驗，但統計上無顯著差異；動作學習後，四種追蹤測驗1-4Hz高峰頻率皆會有顯著的下降，但四種測驗間在相對進步量方面並沒有顯著差異；在6-12Hz高峰頻率，僅在0.75Hz追蹤測驗有顯著下降的趨勢。
結論：學習簡單正弦位移追蹤動作之後，學習成果將有效轉移至複合正弦位移追蹤動作，尤其在提供視覺迴授下，波形的學習與轉移有明顯的加成效果；動作震顫的結構因動作學習而改變，1-4 Hz低頻震顫減少與手眼協調成熟有關；而6-12Hz動作震顫振幅僅在較高頻0.75Hz正弦位移追蹤出現學習後減少的情形，推論中央震顫迴路與反應時間短、傾向開放徑路的學習有關。

Objective: Motor learning is the process of acquisition of movement skill due to repetitive practicing. In general, learning a new motor skill associated with development of a new internal model; Provided that different motor skills share some inherent components of internal models, the effect of learning transfer would be evident. Several previous studies have investigated the motor transferring across limbs, however little attention was paid to the extent to which a complex movement can be benefited from practicing a simple act beforehand, as well as the dependence on visual feedback after learning transfer. In this study, we used the laser system to detect performance of the tracking tasks and associated kinetic tremor to observe the effects of learning transfer on compound sinusoidal tracking consequent to simple sinusoidal tracking with visual feedback. Next, the present study also investigated the significance of visual feedback for tracking task in relation to generalization of internal models.

Methods: Sixteen healthy subjects practiced alternate abduction and adduction with the dominant index finger to couple the position trace with the sinusoidal waves at 0.25Hz and 0.75Hz. Each practice trial consisted of eight 40-second trials which were interlaced with a 40 second resting interval. Pre-test and post-test contained four different position tracking tests: 0.25Hz/0.75Hz sinusoidal tracking, and compound wave (0.25Hz +0.75Hz) with and without visual feedback. Re-test was performed fifteen minutes later after post-test to minimize fatigue effect. Position trace and kinetic tremor were recorded with the laser system. Cross correlation and root mean square (RMS) of position trace and target curves were determined to characterize waveform congruency and performance errors. RMS and tremor peaks in the 1-4 Hz and 6-12 Hz of kinetic tremor were calculated. The amounts of relative changes in all features of kinetic tremor were contrasted among all tracking tests after learning the simple sinusoidal tracking.

Results: After practicing simple sinusoidal tracking, the waveform congruency improved and the total errors decreased in the compound tracking tasks. In reference to simple tracking task, the waveform congruency of compound tracking task with visual feedback was much improved, though reduction in performance errors was not completely dependent on provision of visual feedback. Quantitative tremor analysis showed that practicing resulted in a greater decrement in tremor amplitude in the tests of the 0.75Hz sinusoidal tracking and compound sinusoidal tracking. Specifically, 1-4 Hz tremor peak reduced for all tracking tests, though the amount of relative decrement in 1-4 Hz tremor peak did not differ among various tracking tests. Noticeably, the 6-12 Hz tremor peak decreased merely in the 0.75Hz tracking task after learning the simple sinusoidal tracking task.

Conclusion: After simple sinusoidal tracking, motor learning was evident which could be transferred efficiently to compound position tracking, in support of enhancement of waveform congruency and decrease in mismatch errors. Particularly, visual feedback added to waveform congruency in the compound tracking task. Learning from simple tracking appeared to decrease 1-4 Hz tremor peak during compound position tracking without visual feedback condition, although it was not different among different tracking tests; thus it suggested that low frequency tremor was related to eye-hand coordination. Moreover, modulation of central rhythm related functionally to successful learning in sinusoidal tracking at a higher rate, which is premeditated by open-loop control.

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