Motor Control Laboratory, Kinesiology Program, Arizona State University, Tempe, AZ 85287-0701, USA.
Neurosci Lett. 2011 Mar 29;492(1):47-51. doi: 10.1016/j.neulet.2011.01.051. Epub 2011 Jan 27.
During visually guided manual movements, gaze is usually fixated to a target until a pointing movement is completed to that target, showing gaze anchoring. We previously examined gaze anchoring during a two-segment eye-hand task under a low accuracy constraint. Eye movements were made to predetermined first and second targets, while hand movements were varied across two conditions: (1) stop at the first target and discontinue (HS1) and (2) stop at both the first and the second targets (HS1S2). Young adults previously broke gaze anchoring at the first target only when the second pointing was excluded (HS1). However, older adults did not break gaze anchoring for either condition. The present study further investigated whether young and older adults break gaze anchoring through short-term practice under the same conditions. An HS1 practice proceeded to an HS1S2 practice. The results showed that the timing of terminating gaze anchoring relative to pointing completion oscillated considerably during the HS1 practice until it was stabilized. Conversely, that timing was stable during the HS1S2 practice. Nevertheless, the young adults benefited from the HS1 practice and broke gaze anchoring even when the second pointing was included in HS1S2. This indicates that gaze anchoring to pointing completion is not a prerequisite for the production of subsequent pointing. By contrast, older adults did not improve the timing of gaze anchoring termination for either practice condition, thereby failing to break gaze anchoring. Thus, aging compromises a predictive control of terminating gaze anchoring relative to pointing completion, which is difficult to overcome through short-term practice.
在视觉引导的手动运动中，通常会将目光固定在目标上，直到指向该目标的动作完成，这表现出目光锚定。我们之前在低精度约束下研究了两段式眼手任务中的目光锚定。眼睛运动被引导至预定的第一和第二目标，而手部运动在两种条件下变化：（1）在第一目标处停止并停止（HS1）和（2）在第一和第二目标处停止（HS1S2）。年轻成年人之前只在排除第二次指向时打破了第一目标处的目光锚定（HS1）。然而，老年人在两种情况下都没有打破目光锚定。本研究进一步探讨了年轻和老年成年人是否通过相同条件下的短期练习打破目光锚定。HS1 练习后进行 HS1S2 练习。结果表明，在 HS1 练习期间，终止目光锚定相对于指向完成的时间相当波动，直到稳定。相反，在 HS1S2 练习期间，该时间是稳定的。然而，年轻成年人受益于 HS1 练习，即使在 HS1S2 中包括第二次指向，他们也打破了目光锚定。这表明，指向完成时的目光锚定不是后续指向产生的前提。相比之下，老年人在两种练习条件下都无法改善终止目光锚定的时间，从而无法打破目光锚定。因此，衰老会损害相对于指向完成的终止目光锚定的预测控制，这很难通过短期练习克服。
