背景及目的：過去研究指出老年人在適應視覺運動關係時，由於無法察覺到視覺運動關係的改變，導致老年人不能有效的利用策略性修正 (strategic correction) 來適應視覺運動關係的改變。如果老年人察覺外在環境改變的能力變差是造成適應不良的原因，則在適應前給予老人任務說明應該可以促進老年人的適應。此外，在經過一段時間的適應，老年人是否可以保留當下適應到的能力以便日後使用則是另一個重要的問題。然而任務說明對於老年人動作留存 (motor retention) 的效果尚未明確。因此本研究的目的是要了解是否任務說明可以促進老年人對視覺運動關係改變的適應，以及是否能強化老年人的動作留存。
研究方法：本研究收集20位健康年輕人及20位健康老人，個別隨機分配到無說明組與說明組。所有的受試者都從起始點以觸控筆向指定的目標做連線動作，在連續兩天的實驗中，他們所看到的動作軌跡會被往逆時針旋轉30度。受試者於第一天的實驗進行共392個連線動作，第二天的實驗進行共192個連線動作。在進行適應前，說明組的受試者會被解釋關於視覺回饋被旋轉的狀況，而無說明組的受試者不會給予說明。實驗完成後，對第一天以及第二天適應階段的動作起始方向誤差 (initial direction error)、整體動作固定誤差(constant error of entire movement) 、主要動作固定誤差(constant error of primary submovement)、次動作平滑度(jerk of secondary submovements)做分析。而動作起始方向誤差、整體動作固定誤差、主要動作固定誤差從第一天最後適應階段到第二天最初適應階段的變化為動作留存的表現。誤差增加的程度越大，表示動作留存越差。
研究結果：老年人在兩天的適應期的動作起始方向誤差、整體動作固定誤差和主要動作固定誤差都比年輕人大。此外，次動作平滑度的結果顯示老年人的次動作較年輕人不平滑。若不分年齡來看，說明組在實驗中的動作起始方向誤差和主要動作固定誤差都比無說明組來得低，而且說明組的次動作也比無說明組平滑。更進一步說，這種有無說明的表現差異在老年人中比在年輕人中明顯。動作起始方向誤差、整體動作固定誤差和主要動作固定誤差在動作留存的表現只與年齡有關，與有無說明無關。老年人的動作留存較年輕人差。
結論：在適應視覺運動關係前給予任務說明，能幫助年輕人和老人作出準確的動作，而此幫助對老年人的效果比對年輕人明顯。本研究的結果推論任務說明可幫助受試者建立準確而有效率的動作計劃，因此受試者不需要產生過多的修正性動作。但動作留存的表現不受任務說明影響，而是受年齡影響。

Introduction: Previous studies suggested that the elderly were less
effective in implementing strategic correction during visuomotor adaptation,
mainly due to lack of awareness of the change in visuomotor relation. If
cognitive realization of visuomotor relation is the problem, it is expected that
given instruction prior to adaptation will facilitate adaptation for the elderly.
Another problem for the elderly is to retain the adapted novel visuomotor
relation. Previous studies suggested implicit learning was robust and had less
memory lost after learning. However, it is unclear whether instruction has an
effect on retention. Thus, the aims of this study were to determine if instruction
would facilitate visuomotor adaptation and enhance motor retention for the
elderly.
Methods: Twenty younger and twenty older adults were recruited, and
participants in each age group were randomly assigned to either the groups with
instruction (WI group) or no instruction (NI group). All subjects reached to a
target and visually perceived their hand trajectory which was rotated 30°
counterclockwise on the screen. The subjects made 392 reaches on the first day
and 192 reaches on the second day. The instruction group received instruction
about visual rotation prior to adaptation and the implicit group did not receive
the instruction. The initial direction errors (IDE), constant error of entire
movement (CEE), constant errors of primary submovement (CEP), and the jerk of
secondary submovements were analyzed as the performance in adaptation. The
increases of IDE, CEE, and CEP from the last phase of day 1 adaptation to the
Iearly phase of day 2 adaptation were deemed as retention. The higher the
increase of error, the poor the retention.
Results: Throughout the two-day adaptation, the older subjects generally
had larger IDE, CEE, and CEP than the younger subjects. Besides, the secondary
submovements were less smooth in older subjects than younger subjects.
Regardless of age, the WI group showed less IDE and less CEP than the NI group
throughout experiment. The secondary submovements were smoother in the WI
group than in the NI group. Such instruction effects were larger for the older
group than for the young group. Performance of retention in IDE, CEE, and CEP
only related to age but not instruction. The older subjects had poor retention
than the young subjects.
Conclusions: Prior instruction is beneficial to both younger and older
adults to perform accurate movements in visuomotor adaptation, especially for
the latter. Besides, instruction facilitated the smoothness of secondary
submovements. Our results suggested that instruction might help subjects to
have accurate and efficient motor plan, and thus subjects did not have to
generate many corrective movements. However, the retention of adaptation was
not improved by instruction, but by age.

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