Abstract
Extensive evidence has shown that movement sequences of motor planning are temporarily stored in working memory (WM) and thus interfere with the storage of other information. However, it remains controversial whether holding information in WM would reversely influence motor planning/replanning. The current study addressed this issue by adapting an anti-pointing task that would force motor-replanning. During the experiment, there were two squares constantly on the left and right sides of the screen, respectively. On each trial, a set of letters (set size: 2-6) were first presented, evenly distributed on the two sides of the screen. After the offset of the letters, one of the letters was presented on the center of the screen again and the participant was asked to indicate which side the letter was once on by pointing. There were two blocks, a “pro-pointing only” block and a “pro-pointing + anti-pointing” block for each participant. In the “pro-pointing only” block and half trials of the “pro-pointing + anti-pointing” block, the target letter was light-grey and the participant should move the index finger to touch the square that was on the same side of the target letter. In the other half of trials of the “pro-pointing + anti-pointing” block, the target was red and the movement should be toward the square on the opposite side. The initiation time of hand movement increased when set size increased and one key finding here was that this set size effect was larger for the anti-pointing trials, compared to pro-pointing trials in the “pro-pointing only” block. This finding, with the result that the trajectory of movement became more center-biased with the increase of set size, indicates that holding information in WM slow down motor replanning and affected the execution, suggesting a source competition between movement planning/replanning and cognitive processes.