Muscle memory is what you access whenever you type on a keyboard or automatically punch your PIN into an ATM. A team of researchers at Johns Hopkins who have explored this type of memory, which is often referred to as motor learning, have arrived at some unexpected conclusions. They say whenever you learn an identical or similar muscle memory task faster on the second, third or fourth time around, the reason you do so is because you are benefitting from two different sets of memories — your recall of both the steps to perform the task and the errors you made. "In learning a new motor task, there appear to be two processes happening at once," says Dr. Reza Shadmehr, a professor in the Department of Biomedical Engineering at the Johns Hopkins University School of Medicine. "One is the learning of the motor commands in the task, and the other is critiquing the learning, much the way a 'coach' behaves.”
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To study how motor learning takes place, the research team created an experiment where participants stood in front of a joystick placed beneath a screen. Although participants couldn't see the joystick, it was represented on the screen as a blue dot. At the same time, a target represented by a red dot appeared on the screen, and as volunteers moved the joystick toward it, the blue dot could be programmed to move slightly off-kilter from where they pointed it, creating an error. Experiencing an error, participants adjusted their movement to compensate, and, after a few more trials, began to smoothly guide the joystick to its target.
In the study, the movement of the blue dot was rotated to the left or the right by larger or smaller amounts. The research team discovered volunteers responded more quickly to smaller errors pushing them consistently in one direction and less to larger errors going against the grain of most of the feedback. "They learned to give the frequent errors more weight as learning cues, while discounting those that seemed like flukes," says David Herzfeld, a graduate student in Shadmehr's laboratory who led the study.
The next step in the research, Shadmehr says, will be to find out which part of the brain is responsible for the "coaching" job of assigning weight to different types of error. Meanwhile, the team receives praise for their work so far.
"This study represents a significant step toward understanding how we learn a motor skill," says Dr. Daofen Chen, a program director at the National Institute of Neurological Disorders and Stroke. "The results may improve movement rehabilitation strategies for the many who have suffered strokes and other neuromotor injuries."
Source: Herzfeld DJ, Vaswani PA, Marko M, Shadmehr R. A memory of errors in sensorimotor learning. Science. 2014.