Preliminary Analysis
fatigue
We performed preliminary analyses to: (1) address the potential susceptibility effect; (2) establish whether the paradigm allowed evaluation of motor sequence learning using our chosen parameters; (3) verify that the baseline performance of the participants allocated to the three stimulation groups did not significantly differ; (4) evaluate whether and when there was a transition from motor sequence learning to motor sequence execution; and (5) evaluate whether a speed–accuracy trade-off accounted for reduced RTs during the learned compared with random sequences. A susceptibility effect has been well documented in motor sequence learning studies, with slower RTs on the initial presentation of the learned sequence following random sequences [Motor sequence learning is an ongoing process. Once a sequence has been learned, faster RTs to the learned than to a random sequence reflect faster execution of the already learned sequence, as well as ongoing learning through further repetition. An overall slowing of RTs to both sequence types over the course of the experiment is consistent with fatigue. To assess whether there was a clear transition from ongoing learning to execution, we examined RTs to learned and random sequences separately for all three study phases. In all phases, RTs to learned sequences were faster than to random sequences, indicating that motor sequence learning took place early in the experiment, and the effect was maintained. During the baseline phase, RTs to learned sequences slowed over time but were faster following each brief break. The finding is consistent with ongoing motor sequence learning throughout the baseline phase, but with superimposed effects of fatigue while the task was continuously performed. In the next phase (online), RTs were again consistently faster during the learned than random sequence. RTs progressively slowed over time, however, during both sequence types, but more during the random than learned sequence. The slowing is again likely to reflect fatigue. The trend towards an interaction between The faster RTs were not at the expense of accuracy, as accuracy was significantly greater during the learned than the random sequences. Moreover, the composite score, IES, reflecting both RTs and accuracy, indicated that overall performance in our participant group was better during the learned than random sequences. Indeed, the application of a repeated measures ANOVA to the IES yielded analogous findings to the ANOVA applied to RTs. As the paradigm is designed to measure motor sequence learning according to RTs [