Learning and Reproduction of Memorized Sequences of Right and Left Hand Movements

An important stage in learning, i.e., the acquisition of a new skill, is the repetitive reproduction of a sequence of movements, which plays a significant role in the formation of motor stereotypies. Two groups of right-handed subjects reproduced (6–10 repeats) sequences of movements guided by the experimenter, sequences consisting of six positions, first with the right hand (RH) and then with the left hand (LH) or vice versa. In series 1, an unfamiliar random sequence was reproduced; series 2 and 3 involved reproduction of modified sequences whose elements were in the same positions but in a different order. The processes of reproduction proceeded similarly for the RH and LH. Learning of the modified sequence was different: regardless of order of presentation, information about the positions of the elements of the sequence was used only when the LH performed the task first. This information was not used when the LH operated after the RH or when the RH performed the task. Thus, the means of encoding information activated on operation by the LH promoted learning of the position memorization task, while that activated by the RH interfered. This appears to be linked with the predominant roles of the right hemisphere in encoding positions and in motor learning processes.