How the brain translates intent into muscle movements

Font Size

Print

Feedback

Email

Discuss

Save & Share Article

What’s this?

Digg	My Yahoo	Fark
del.icio.us	Newsvine	Reddit

Rate This Article

Rating:  0

Friday , May 09, 2008 at 2333 hrs Ever guessed how your brain translates your simple intent to perform an action — for example, downing a glass of chilled beer —into the dynamic and coordinated symphony of muscle movements?

Well, the neural instructions for such actions originate in the brain’s primary motor cortex, and the puzzle has been whether the neurons in this region encode the details of individual muscle activities or high-level commands which govern the direction and velocity of desired movements.

Now, Robert Ajemian and his colleagues, analysing muscle function in monkeys, have created a mathematical model that captures the control characteristics of the motor cortex, the Neuron reported in its latest edition.

In fact, the model enabled the researchers to better sort out the “muscles-or-movement” question. Researchers have been thwarted in their efforts to measure and model the neural control of complex motions as muscle forces and positions constantly change during such motions.

Also, the position sensors, called proprioceptors, in joints and muscles feed back constantly changing signals to the neurons of the motor cortex. The researchers overcame these complexities by simplifying the experimental design. Rather than asking monkeys to carry out complex movements, they trained the animals to push on a joystick in different, specified ways to move a cursor on a screen to a desired target.

This use of isometric force greatly simplified the measurements the researchers needed to make to define muscle and joint action. As the monkeys carried out the isometric tasks, the researchers analysed the patterns of muscle activations that corresponded with the isometric forces in different directions and at different postures.