Certain motor skills are likely to be remembered for longer if learnt slowly, according to a study published online in PLoS-Biology yesterday. The findings could have important implications for rehabilitation procedures for victims of stroke and other types of brain injury.
Smith, et al devised a simple task – operating a robot-controlled joystick – to demonstrate that, over short timescales, two distinct processes are involved in the adaptive learning of motor skills. Participants were asked to hold onto the joystick and prevent it from moving when the robot motor pushed it to one side.
The joystick precisely measured hand position, velocity and force exerted on it, and computer programs were used to perform mathematical operations on the measurements. Predictions of how the brain acquires motor skills were then made from these calculations. Although the robot motor had been programmed to push the joystick in several directions, it was found that participants tended to push in the first direction they had learnt, even when the joystick was stationary.
From the number of repetitions needed for participants to learn the first movement, and how long it took them to forget the amount of force needed to keep the joystick stationary, the predictions suggested that the brain learns such muscle movements in two steps.
Using the computer programs, the researchers determined that although the movements needed to keep the joystick stationary were easily learnt and quickly forgotten, the brain was also processing the same information using another, slower mechanism. This second mechanism accounts for the inclination of the participants to use the first movements they learnt for different tasks later on. "Our work…implies that the best strategy in rehabilitating a stroke patient should focus on slow learning because slow-learned motor skills will be maintained longer," says senior author Reza Shadmehr, a professor of biomedical engineering at the Institute of Basic Biomedical Sciences at Johns Hopkins University.
It was widely believed that both time and error are required for motor learning; the former for the brain to process and consolidate new information, and the latter for fine-tuning the movements. This study contradicts the belief, by showing that motor skills can be learnt in very short periods of time.