The nature of savings associated with a visuomotor adaptation task that involves one arm or both arms.

The nature of savings in visuomotor adaptation is typically studied using a paradigm in which one arm experiences multiple conditions such as adaptation, washout and readaptation. It has seldom been studied, however, using a paradigm that involves both arms. Here, we examined the effect of (1) using different arms and (2) the availability of visual feedback during a washout session following visuomotor adaptation on savings. We first had healthy young adults adapt to a visuomotor rotation condition during reaching movements with the left arm. Following that, they experienced a washout session with either the left or right arm, with or without visual feedback, and then the readaptation session with the left arm again. We hypothesized that if savings occurred due to the explicit recall of cognitive strategies, the pattern of savings would be similar regardless of which arm was used during the washout session. Results showed that in terms of the percentage of savings, there was a significant difference between the conditions in which the left or right arm was used during the washout, but not between the conditions in which visual feedback was provided or absent. In terms of the rate of relearning, a significant difference was observed between the conditions in which the left or right arm was used during the washout, and also between the conditions in which visual feedback was provided or absent. These findings suggest that the explicit recall of strategies is not the only source for savings and further suggest that effector-specific, use-dependent learning can also contribute to savings.

A positive association between active lifestyle and hemispheric lateralization for motor control and learning in older adults.

Physical activity (PA) is well known to have general health benefits for older adults, but it is unclear whether it can also positively affect brain function involved in motor control and learning. We have previously shown that interlimb transfer of visuomotor adaptation occurs asymmetrically in young adults, while that occurs symmetrically in older adults, which suggests that the lateralized function of each hemisphere during motor tasks is diminished with aging. Here, we investigated the association between the level of PA and hemispheric motor lateralization by comparing the pattern of interlimb transfer following visuomotor adaptation between physically active and inactive older adults. Subjects were divided into two groups based on their PA level (active, inactive). They were further divided into two groups, such that a half of the subjects in each group adapted to a 30° rotation during targeted reaching movements with the left arm first, then with the right arm; and the other half with the right arm first, then with the left arm. Results indicated asymmetrical transfer (from left to right only) in the active subjects, whereas symmetrical transfer (from left to right, and vice versa) was observed in the inactive subjects. These findings suggest that older adults who maintain active lifestyle have a central nervous system that is more intact in terms of its lateralized motor function as compared with those who are inactive.