title: Probabilistic Motor Sequence Yields Greater Offline and Less Online Learning than Fixed Sequence.
abstract: It is well acknowledged that motor sequences can be learned quickly through online learning. Subsequently, the initial acquisition of a motor sequence is boosted or consolidated by offline learning. However, little is known whether offline learning can drive the fast learning of motor sequences (i.e., initial sequence learning in the first training session). To examine offline learning in the fast learning stage, we asked four groups of young adults to perform the serial reaction time (SRT) task with either a fixed or probabilistic sequence and with or without preliminary knowledge (PK) of the presence of a sequence. The sequence and PK were manipulated to emphasize either procedural (probabilistic sequence; no preliminary knowledge (NPK)) or declarative (fixed sequence; with PK) memory that were found to either facilitate or inhibit offline learning. In the SRT task, there were six learning blocks with a 2 min break between each consecutive block. Throughout the session, stimuli followed the same fixed or probabilistic pattern except in Block 5, in which stimuli appeared in a random order. We found that PK facilitated the learning of a fixed sequence, but not a probabilistic sequence. In addition to overall learning measured by the mean reaction time (RT), we examined the progressive changes in RT within and between blocks (i.e., online and offline learning, respectively). It was found that the two groups who performed the fixed sequence, regardless of PK, showed greater online learning than the other two groups who performed the probabilistic sequence. The groups who performed the probabilistic sequence, regardless of PK, did not display online learning, as indicated by a decline in performance within the learning blocks. However, they did demonstrate remarkably greater offline improvement in RT, which suggests that they are learning the probabilistic sequence offline. These results suggest that in the SRT task, the fast acquisition of a motor sequence is driven by concurrent online and offline learning. In addition, as the acquisition of a probabilistic sequence requires greater procedural memory compared to the acquisition of a fixed sequence, our results suggest that offline learning is more likely to take place in a procedural sequence learning task.
authors.affiliation: Department of Kinesiology, University of MarylandCollege Park, MD, USA; Applied Mathematics and Statistics, and Scientific Computation Program, University of MarylandCollege Park, MD, USA.
authors.forename: Yue
authors.initials: Y
authors.lastname: Du
authors.affiliation: Department of Kinesiology, University of MarylandCollege Park, MD, USA; Neuroscience and Cognitive Science Program, University of MarylandCollege Park, MD, USA.
authors.forename: Shikha
authors.initials: S
authors.lastname: Prashad
authors.affiliation: Department of Kinesiology, University of Maryland College Park, MD, USA.
authors.forename: Ilana
authors.initials: I
authors.lastname: Schoenbrun
authors.affiliation: Department of Kinesiology, University of MarylandCollege Park, MD, USA; Neuroscience and Cognitive Science Program, University of MarylandCollege Park, MD, USA.
authors.forename: Jane E
authors.initials: JE
authors.lastname: Clark
keywords: declarative memory; fast motor sequence learning; offline learning; online learning; probabilistic sequence; procedural memory; sequence knowledge