A, General procedure. All participants completed a learning, fMRI, and retention session during which they performed a SRTT (see panel B). Depending on the task condition, cues in the SRTT followed a random (RND) or repeating, sequential (SEQ) pattern. During the learning and retention sessions, the task took place outside the scanner and was organized in blocks of practice. During the fMRI session, data were acquired over eight consecutive scanning runs during which RND and SEQ SRTT conditions randomly alternated. B, Task. During the SRTT, participants were instructed to press as quickly and accurately as possible the key corresponding to the location of a cue (green filled square; response to stimulus interval; RSI, 1.5–2.5 s; average 2 s). The repeating pattern in the SEQ SRTT consisted of eight key presses (4-7-3-8-6-2-5-1, with 1 and 8 corresponding to the little fingers of the left and right hand, respectively), and in this pattern, each finger was used once. In the RND SRTT, there was no fixed pattern, but each key was pressed once every eight key presses. During both the RND and SEQ SRTT, the serial position of a key press in a stream of eight key presses was indicated by green asterisks on top of the screen. C, Structure of neural similarity matrices. Pattern similarity was computed across repetitions of the motor sequence to assess finger-position coding in the sequence (SEQ matrix) as well as across repetitions of the random patterns to quantify coding of individual finger movements/key presses irrespective of position (RK matrix) and positions irrespective of movements (RP matrix) in random movement patterns. Pairs of movements sharing a particular type of information (same finger + position in the SEQ matrix, same finger in the RK matrix, or same position in the RP matrix) are represented on the diagonal of each matrix.