Study design.

(A) sequential finger tapping task. A sequence initially trained on the Day 1 (T-Seq, left panel) and a novel sequence used during the interference training on Day 2 (Int-Seq, right panel). The two sequences were matched for number of movements per digit and mirror-reversed in relation to each other (in terms of order). (B) Experimental groups. On Day 1 all groups underwent training on the T-Seq consisted of 14 performance blocks. On Day 2 the memory for the T-Seq was retrieved (or not) using one performance block and the interference training on the novel Int-Seq was conducted according to the experimental group (NoReInt, ReInt and Re8hInt). On Day 3 the performance levels for the T-Seq were tested in all groups using 7 performance blocks; the performance for the Int-Seq was subsequently tested as well. In all sessions performance blocks consisted of 60 key-presses, equivalent to 12 possible sequences, and were separated by 25-second periods of rest.