Fig. 2.

Experimental design and structure of event-related functional magnetic resonance imaging (fMRI) analysis. A: the training session presented participants with alternating trial epochs organized in both block (B) and random schedule (R) form. Each schedule epoch contained 18 sequence preparation (no go) and 18 sequence production (go) trials. Participants received 6 schedule epochs: 3 block schedules and 3 random schedules each lasting 139 scans. Presentation of block and random epochs were interleaved, such that following the completion of all trials contained in a block schedule, the next epoch of trials would be presented using a random schedule. For the test session participants received 2 epochs of trials comprised of all the practiced sequences, independent of initial practice schedule. One epoch contained trials organized into miniblocks of 3 trials of the same sequence (Tb) and the other epoch presented trials in a random order (Tr). For each epoch, trials could be either preparation or production events. Epochs continued until participants produced 18 correct sequences. B: to account for behavioral performance differences between schedules within the fMRI analysis, the training trials were grouped into thirds. The first third of trials, shown in solid white, are known as “early training events,” whereas the final two thirds of trials, shown with line patterns, are known as “late training events.” Early and late training events were defined by the amount of training time for each sequence. Such that, the first third of trials (6 trials) for a particular sequence were considered early events, and the final two thirds of trials (12 trials) for the same sequence were considered late events. This was done separately for both preparation (no go) and production events (go). Because only one sequence was presented in each block schedule, early events were considered to be the first third of each block epoch and late events were from the final two thirds of each block epoch. On the other hand, all 3 random schedule sequences were presented in each random schedule epoch, so that the early events were considered to be the first random epoch, whereas the final 2 random epochs were classified as late events. A total of 18 early events and 36 late events were designated for both block and random schedules.