Evidence for effector independent and dependent representations and their differential time course of acquisition during motor sequence learning
Evidence for effector independent and dependent representations and their differential time course of acquisition during motor sequence learning
复制标题
DOI：
10.1007/s002219900332
复制
发表时间：
2000-05-01
影响因子：
2
通讯作者：
Harner, AM
中科院分区：
文献类型：
--
作者：
Bapi, RS;Doya, K;Harner, AM
为了研究动作序列的表征，我们在一个动作序列学习范式中测试了迁移效应。我们假设有两种序列表示，效应独立和依赖。此外，我们假设效应器独立表征在视觉/空间坐标中，效应器依赖表征在运动坐标中，并且他们在学习过程中习得的时间过程是不同的。12名受试者接受了修改后的2x10任务测试。受试者学会了连续按下键盘上的两个键（称为一组键），以响应3x3显示屏上的两个亮着的方块。要学习的完整序列由十个这样的集合组成，称为超集合。在正常条件下进行训练，并在正常、视觉和运动三种条件下分别在早期、中期和后期评估序列回忆。在视觉条件下，手指键盘映射旋转90度，而键盘显示映射保持正常。在运动条件下，键盘显示映射也旋转90度，导致与正常情况下相同的手指显示映射。受试者分为两组，每组使用不同的正常状态。一组在标准键盘设置中学习序列，随后在测试条件下使用旋转键盘设置回忆序列。第二组在旋转键盘设置下学习序列，随后在测试条件下用标准键盘设置回忆序列，记录回忆过程中的反应时间（RT）和序列错误。尽管与正常情况相比，受试者在视觉和运动两种测试条件下都犯了更多的排序错误，但错误低于概率水平。排序错误在视觉和运动条件下没有显著差异。此外，即使在受试者第一次在视觉和运动条件改变的情况下进行序列回忆的早期阶段，序列回忆的正确率也超过70%。这些序列知识在使用不同手指运动的条件下的正迁移结果指向了一种独立于效应器的序列表示，可能是在视觉/空间坐标中。最初的RTs在视觉和马达上都很相似。在重复测量方差分析中，运动条件下的RTs显著短于视觉条件下的RTs，这表明测试阶段和条件项之间存在显著的相互作用。此外，以三种条件下的单按键RTs作为基准指标，再次观察到视觉和运动条件下的RTs在早期没有显著差异，但运动RTs在测试后期显著缩短。这些结果支持了一个假设，即运动条件比视觉条件更有利，因为它使用与正常条件相同的效应运动。此外，这些结果证明了在运动坐标中存在依赖于效应器的序列表示，这是相对缓慢地获得的。这两种表征在学习过程中的时间差异可能解释了在损伤和想象研究中发现的早期和晚期学习阶段大脑区域的不同受累。
To investigate the representation of motor sequence, we tested transfer effects in a motor sequence learning paradigm. We hypothesize that there are two sequence representations, effector independent and dependent. Further, we postulate that the effector independent representation is in visual/spatial coordinates, that the effector dependent representation is in motor coordinates, and that their time courses of acquisition during learning are different. Twelve subjects were tested in a modified 2x10 task. Subjects learned to press two keys (called a set) successively on a keypad in response to two lighted squares on a 3x3 display. The complete sequence to be learned was composed of ten such sets, called a hyperset, Training was given in the normal condition and sequence recall was assessed in the early, intermediate, and late stages in three conditions, normal, visual, and motor. In the visual condition, finger-keypad mapping was rotated 90 degrees while the keypad-display mapping was kept identical to normal. In the motor condition, the key pad-display mapping was also rotated 90 degrees, resulting in an idenitical finger-display mapping as in normal. Subjects formed two groups with each group using a different normal condition. One group learned the sequence in a standard keypad-hand setting and subsequently recalled the sequence using a rotated keypad-hand setting in the test conditions. The second group learned the sequence with a rotated keypad-hand setting and subsequently recalled the sequence with a standard keypad-hand setting in the test conditions, Response rime (RT) and sequencing errors during recall were recorded. Although subjects committed more sequencing errors in both testing conditions, visual and motor, as compared to the normal condition, the errors were below chance level. Sequencing errors did not differ significantly between visual and motor conditions. Further, the sequence recall accuracy was over 70% even by the early stage when the subjects performed the sequence for the first time with the altered conditions, visual and motor. There were parallel improvements thereafter in all the conditions, These results of positive transfer of sequence knowledge across conditions that use dissimilar finger movements point to an effector independent sequence representation, possibly in visual/spatial coordinates. Initially the RTs were similar in the visual and the motor. conditions, but with training RTs in the motor condition became significantly shorter than in the visual condition, as revealed by significant interaction for the testing stage and condition term in the repeated measures ANOVA. Moreover, using RTs for single key pressing in the three conditions as baseline indices, it was again observed that RTs in the visual and motor conditions were not significantly different in the early stage, but motor RTs became significantly shorter by the late testing stage. These results support the hypothesis that the motor condition benefits more than the visual because it uses identical effector movements to the normal condition. Further, these results argue for the existence of effector dependent sequence representation, in motor coordinates, which is acquired relatively slowly. The difference in the time course of learning of these two representations may account for the differential involvement of brain areas in early and late learning phases found in lesion and imagine studies.