CAMBRIDGE, Mass., January 7, 2010 – Bioengineers have taken a small step toward
improving physical recovery in stroke patients by showing that a key feature of
how limb motion is encoded in the nervous system plays a crucial role in how
new motor skills are learned.

Published in the November 25, 2009 issue of Neuron, a Harvard-based study about
the neural learning elements responsible for motor learning may help scientists
design rehabilitation protocols in which motor adaptation occurs more readily,
potentially allowing for a more rapid recovery.

Neuroscientists have long understood that the brain's primary motor cortex and
the body's low-level peripheral stretch sensors encode information about the
position and velocity of limb motion in a positively-correlated manner rather
than as independent variables.

"While this correlation between the brain's encoding of the position and the
velocity of motion is well-known, its potential importance and practical use
has been unclear until now," says coauthor Maurice A. Smith, Assistant
Professor of Bioengineering at the Harvard School of Engineering and Applied
Sciences (SEAS) and the Center for Brain Science in the Faculty of Arts and
Sciences.

Smith and colleagues showed that the correlated neural tuning to position and
velocity is also present in the neural learning elements responsible for motor
learning. Moreover, this correlated drive can explain key features of the motor
adaptation process.

To study and record motor adaptation, the researchers had subjects grasp a
robotic arm. The device was programmed to simulate novel physical dynamics as
subjects made reaching motions. In addition, the team used a newly developed
measurement technique called an "error-clamp" to tease apart the resulting
data.

The method measures motor output during learning, allowing learning-related
changes in motor output over the course of a movement to be dissociated from
feedback adjustments that correct motor errors that happen simultaneously.

Full story http://www.eurekalert.org/pub_releases/2010-01/hu-oah010710.php