To move a computer mouse, point to icons on a touch screen, lift a fork from plate to mouth-all these routine movements pose big challenges for movement experts. Researchers like Luc Proteau, Professor in the Department of Kinesiology at Université de Montréal, are trying to learn more about them. "We want to get a better understanding of how the human brain operates when it processes the sensory information needed for movements. We call that the role of sensory afferents in planning, controlling and learning movement," the researcher remarks.

The knowledge acquired in his laboratory could have applications in robotics and medicine, for example, by improving the motor functions of robots used in space or helping to develop implants for patients with cerebral lesions.

Professor Proteau was motivated by a simple question: for a person who performs the same gesture thousands of times in a given task, does the importance of sensory information decrease to the point that he can carry out the movement "with eyes closed"? "The great majority of people think-and I also thought-that when the same gesture is repeated, vision becomes less and less important in performing a movement. But this is wrong."

In an experiment that he performed, individuals had to touch a light target situated to 85 centimeters with their finger, repeating the action 200 to 2000 times! Then, when the subjects were placed in the dark, they would miss the target by 15 centimeters. He concludes that even after hundreds, or even thousands of tests, vision remains essential for the precision of movements. "In fact, the more you perform a movement that requires vision, the more necessary vision becomes in performing it properly," Prof. Proteau explains. In another surprise, the researcher found that an older person's movements are just as precise as a young person's. "We showed that the elderly are just as precise as normal young adults," he explains. "What varies is the speed of processing of sensory data, which decreases with age."

With a student in the Ph.D., Léna Lhuisset, Luc Proteau has just demonstrated that children undergo a decisive stage in their cognitive development at six years of age. When they have to perform a visual or manual pointing task such as moving a mouse so that the cursor moves on the screen, a six year-old child plans the movement using internal coordinates (angle of arm and forearm, force to apply, etc.) whereas a 10 year-old child or adult plans the movement with external coordinates. "This means there is a transition in the way this type of movement is planned as the person develops," the researcher explains.

Researcher: Luc Proteau
Telephone: (514) 343-2039
Funding: Natural Science and Engineering Research Council