Research Article: Effects of the amount of practice and time interval between practice sessions on the retention of internal models

Date Published: April 16, 2019

Publisher: Public Library of Science

Author(s): Chiharu Yamada, Yoshihiro Itaguchi, Kazuyoshi Fukuzawa, Karsten Witt.

http://doi.org/10.1371/journal.pone.0215331

Abstract

The amount of practice and time interval between practice sessions are important factors that influence motor learning efficiency. Here, we aimed to reveal the relationship between the retention and consolidation of a new internal model, and the amount of practice and time interval between practice sessions. We employed a visuomotor rotation tracking task to test the hypotheses that (1) a new internal model consolidates owing to extensive practice after reaching a task performance plateau and (2) a longer time interval between practice sessions makes it difficult to activate a new internal model. The participants were assigned to one of the four groups that differed in terms of the amount of practice and the time interval between practice sessions. They performed a tracking task in which they experienced 120° clockwise visuomotor rotation and were required to track a moving target on a computer display using a mouse cursor. To evaluate the retention and consolidation of a new internal model, we calculated the aftereffects and savings as measures of motor learning. To the best our knowledge, this is the first study to manipulate both the amount of practice and the time interval between practice sessions simultaneously in one experiment using a visuomotor tracking task. Our results support the previously reported idea that extensive practice is necessary for the consolidation of a new internal model.

Partial Text

The efficiency of human motor learning is significantly enhanced by minimizing the amount of practice, while maximizing the time interval between practice sessions without losing what is learned. Various studies have been conducted to model the optimal method of practice for maximizing motor learning performance [1]. For example, the effects of practice conditions, such as contextual interference and knowledge of results [2–4] and physical fatigue [5] on performance have been investigated. Besides these factors, we focus on the practice schedule, i.e., the duration of practice and the time interval between practice sessions. For people who try to learn or improve a new motor skill, a critical problem is how long they should practice in a day and how many days of rest they are allowed between sessions to maintain their skills. Therefore, to establish a method for efficient motor learning, it is necessary to determine the effects of the amount of practice and the time interval between practice sessions on motor learning.

We calculated the errors in the tracking task for two days to investigate the effect of the amount of practice and time interval between practice sessions on the retention and consolidation of a new internal model. Although all participants noticed the rotation of the cursor in the practice sessions, they could not describe the rotation. Fig 3 shows the changes in the errors of the 24-h-interval groups, and Fig 4 shows those of the 48-h-interval groups. The horizontal axis represents the number of sessions, and the vertical axis represents the task errors.

The present study investigated the effect of the amount of practice and the time interval between practice sessions on the retention and consolidation of a new internal model. We hypothesized that (1) a new internal model consolidates owing to extended practice after reaching a task performance plateau and (2) a longer time interval between practice sessions prevents the new internal model from being activated. The results of the tracking task for two days revealed that the magnitude of the aftereffects and the savings changed depending on the amount of practice, while the time interval between practice sessions affected the aftereffects only when the participants practiced longer. Specifically, the aftereffects in the 20-session groups (Group 2 and Group 4) were greater than those in the 10-session groups (Group 1 and Group 3) on Day 1 and Day 2 regardless of the time interval between the experimental sessions. In the 48-h-interval condition, the aftereffects decreased on Day 2 compared to Day 1, where the participants performed 20 sessions of the task on Day 1 (Group 4). In addition, the savings were greater in the 20-session groups (Group 2 and Group 4) than in the 10-session groups (Group 1 and Group 3), regardless of the time interval. These results supported the first hypothesis, but not the second one. By using a tracking task, the present study revealed for the first time that additional practice after reaching a task performance plateau is important for the consolidation of a new internal model.

The present study aimed to reveal the relationship between the amount of practice and time interval between practice sessions and the retention and consolidation of a new internal model for efficient motor learning. Two main suggestions were provided. First, additional practice after reaching a task performance plateau is important for the consolidation of a new internal model. Second, two-day rest does not negatively affect the learning of a simple visuomotor task. We emphasize here that the present study provided suggestions consistent with those of previous studies regardless of the type of motor learning task. The suggestions of this study might eliminate the extra time and labor required for motor learning, streamline rehabilitation in clinical settings, and facilitate efficient sports training.

 

Source:

http://doi.org/10.1371/journal.pone.0215331

 

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