The Structural Relationship Between Two Motor Sequences Practiced Close in Time Impacts Offline Facilitation

ABSTRACT

Robust offline gains occur during explicit motor sequence learning. However practice of a motor sequence, other than the target sequence, within 4–6 hr after initial practice interferes with these gains. This work assessed if experiencing supplemental practice of spatially or motorically similar sequences influenced the extent of offline gain. A contemporary model of sequence learning assumes that exposure to a spatially but not motor-related sequence would not compromise stabilization of the memory for the target sequence, thus, would have minimal impact on the resultant offline gain and possibly amplify overnight gains. As anticipated, a reliable offline improvement was observed for the target motor sequence in the absence of practice with an alternative motor sequence. This gain was significantly reduced when the learner experienced additional practice with either a novel or motorically similar sequence. There was no evidence of heightened overnight gain for the target sequence from intervening practice with a spatially similar sequence. Thus, the expression of offline improvement is not necessarily eliminated if practice of an alternative motor sequence is encountered shortly after a target sequence. However, the structure of the motor sequence faced during intervening practice can impact the resultant postpractice consolidation processes reflected in the eventual expression of offline facilitation.

Keywords:

• sequence learning
• motor learning
• consolidation
• explicit learning
• offline gain

ACKNOWLEDGMENTS

The authors thank two anonymous reviewers for suggesting the inclusion of the Explicit and Implicit Learning of Sequential Skills section.

Notes

1. There has been some discussion recently regarding the specific contributions of time and sleep to the stabilization process. While this debate is outside the scope of the present work, brief overviews of this debate are offered elsewhere by (Diekelmann & Born, 2007; Song, 2009).

2. In Walker et al. (2003) the use of these tasks was counterbalanced with respect to being used as the target and interference task.

3. This expectation is based on using speed as the dependent variable, which is expected to increase with practice. Obviously, the reverse effect is anticipated for accuracy, which is expected to decrease with practice.