Development of a Portable Motor Learning Laboratory (PoMLab)

Abstract

Most motor learning experiments have been conducted in a laboratory setting. In this type of setting, a huge and expensive manipulandum is frequently used, requiring a large budget and wide open space. Subjects also need to travel to the laboratory, which is a burden for them. This burden is particularly severe for patients with neurological disorders. Here, we describe the development of a novel application based on Unity3D and smart devices, e.g., smartphones or tablet devices, that can be used to conduct motor learning experiments at any time and in any place, without requiring a large budget and wide open space and without the burden of travel on subjects. We refer to our application as POrtable Motor learning LABoratory, or PoMLab. PoMLab is a multiplatform application that is available and sharable for free. We investigated whether PoMLab could be an alternative to the laboratory setting using a visuomotor rotation paradigm that causes sensory prediction error, enabling the investigation of how subjects minimize the error. In the first experiment, subjects could adapt to a constant visuomotor rotation that was abruptly applied at a specific trial. The learning curve for the first experiment could be modeled well using a state space model, a mathematical model that describes the motor leaning process. In the second experiment, subjects could adapt to a visuomotor rotation that gradually increased each trial. The subjects adapted to the gradually increasing visuomotor rotation without being aware of the visuomotor rotation. These experimental results have been reported for conventional experiments conducted in a laboratory setting, and our PoMLab application could reproduce these results. PoMLab can thus be considered an alternative to the laboratory setting. We also conducted follow-up experiments in university physical education classes. A state space model that was fit to the data obtained in the laboratory experiments could predict the learning curves obtained in the follow-up experiments. Further, we investigated the influence of vibration function, weight, and screen size on learning curves. Finally, we compared the learning curves obtained in the PoMLab experiments to those obtained in the conventional reaching experiments. The results of the in-class experiments show that PoMLab can be used to conduct motor learning experiments at any time and place.

Sub-optimality in motor planning is retained throughout 9 days practice of 2250 trials

“…In these situations, humans can learn a less variable motor response to a target456789 and can also adapt movement to reach a target under a novel environment, with perturbation produced by visuo-motor rotation or force field31323334353637. The basic model of motor learning proposes that learning occurs by updating the internal model based on an error (discrepancy) between the target and the resulting motor output in a trial-by-trial basis323537.…”

Larger, but not better, motor adaptation ability inherent in medicated Parkinson’s disease patients revealed by a smart-device-based study

“…In contrast to the adaptation to an abrupt perturbation, PD patients showed a compatible adaptation ability with healthy elderly individuals in responding to a gradually applied visuomotor transformation (we refer to this type of perturbation as a gradual perturbation hereafter) 12,13 . In contrast to abrupt perturbations, a striking feature of gradual perturbations is their difficulty in being noticed [9][10][11]14,15 . A task switch can thus be related to an adaptation to the abrupt perturbation and not to an adaptation to the gradual perturbation.…”

“…For example, when the perturbation was 90 degree visuomotor rotation that caused a 90 degree deviation in the movement angle between the actual and perturbed movements, it was possible to achieve the desired movements by aiming at the 90 degree location distant from a target. With an abrupt perturbation, subjects tend to notice the onset of the perturbation or task switching [9][10][11] . In the motor adaptation to the abrupt perturbation, it is difficult to determine whether the impaired sensorimotor adaptation in PD patients is caused by their cognitive abilities (i.e., the influence of the task switch) or adaptation abilities.…”

“…Here, we investigated the motor adaptation ability of PD patients while decreasing the influence of the task switch as much as possible. To reduce the influence of the task switch, we relied on a gradually applied perturbation whose existence was noticeable by 1 out of the 82 participants in our previous study 11 ; the visuomotor rotation changed by one degree in each trial, and the maximum value of the rotation was 15 degrees. Based on a previous study, task switches are less involved in gradually applied 15-degree visuomotor rotation than in gradually applied 45-degree visuomotor rotation 9 .…”

“…Smart-device-based experiments have been proposed to conveniently investigate motor adaptation or visuomotor abilities for flexible applications 21,22 . Our smart-device-based setting has been validated under several conditions and by comparing it to a conventional experimental setting with manipulanda 11 . We refer to our experimental setting as the POrtable Motor learning LABoratory (PoMLab).…”