Motor Sequence Learning is Independent of Spacing, Micro-consolidation, and Reactive Inhibition

For declarative memory tasks, spaced training has repeatedly been shown to yield more learning than massed training. Recent evidence from Gupta & Rickard (in press) tentatively suggests that spacing may also facilitate motor sequence learning, by either promoting learning during breaks (micro-consolidation), decreasing reactive inhibition (RI), or both. The micro-consolidation hypothesis states that motor learning occurs during breaks via hippocampal-neocortical replay, such that more frequent breaks may facilitate learning. RI refers to a pattern of worsening performance during continual task training that dissipates during breaks. Prior work is inconclusive regarding whether RI may also attenuate learning. During the training phase of a motor sequence task, we jointly manipulated two pertinent factors – the number of correct sequences per trial and the break period between trials – while holding the total number of correct training sequences constant. On a later test, groups were equated on both of those factors. In each of the two experiments, a pronounced performance difference between groups was observed at the end of training. Nevertheless, performance on the test was statistically indistinguishable. Hence, it appears that RI had little or no effect on learning and that micro-consolidation during breaks either did not occur or did not depend on the duration and distribution of breaks. Our results indicate that, at least under some circumstances, spaced training does not facilitate motor skill learning.