They say practice makes perfect, but when it comes to skills involving movement and coordination, a more critical factor appears to be the simple passage of time.
The first six hours after a motor skill--such as riding a bicycle--is learned comprise a window of vulnerability during which the skill can be impaired or even lost by attempting to learn a second motor task. During those hours, researchers from the University of Maryland School of Medicine and Johns Hopkins University School of Medicine say, the central nervous system is consolidating a pattern of neural pathways that control performance of the task, moving them from one part of the brain to others in the process.
Dr. Henry H. Holcomb, professor of psychiatry at the University of Maryland, and Dr. Reza Shadmehr, a biomedical engineering professor at Johns Hopkins, report their findings in the August 8, 1997 issue of Science. What they've learned could change the way skills training is conducted in educational and industrial settings.
"We wanted to know if the neural representation of a motor task change with time in the absence of practice," Holcomb said.
Using positron emission tomography (PET) imaging to monitor changes in cerebral blood flow, the researchers taught study participants a new skill involving rapid, accurate movements of a motorized robotic arm. Imaging brain blood flow is a way of tracking neural activity.
They found that during the critical first five to six hours, the neural links that form the brain's internal model of the task shift from the prefrontal regions of the cerebral cortex to the premotor, posteriorparietal and cerebellar areas. Even without practice, after five or six hours, the recipe for the task is virtually hardwired into the brain. That's why an adult who learned to ride a bicycle as a child can climb on a bike 20 years later and pedal away, Holcomb said.
"The representation of a motor task is fragile immediately after learning it, but it becomes progressively more resistant to modification with the passage of time. After about five to six hours, a person's retention and neural representation of a task is stable," he explained.
"This paper demonstrates that time's passage causes the brain actually to represent the task using different neural pathways," Holcomb added. "We believe that this shift in neural representation is an important aspect of memory consolidation."
The study reported in Science laid the groundwork for the scientists current research: using PET imaging to examine what happens in the brain when interference occurs during the window of vulnerability, before motor memory is consolidated. It was funded in part by the Whittaker Foundation, the National Institute of Mental Health and the Office of Naval Research.