In a body without balance impairment, the nervous system collects sensory information from all over the body and transmits this information to the muscles that control balance. Impairments and injuries to the nervous system or the senses that report to the nervous system lead to balance problems.
Georgia Tech and Emory researchers set out to create an effective way to interpret how commands from the nervous system to muscles (measured through electrical signals in the muscles) are changed by sensory impairment and how these changes affect balance control.
The researchers hypothesized that the nervous system relies on the relationship between the body’s center of gravity and its environment to control balance. They reasoned that the best predictor of how muscles would be activated when the subject experienced a balance threat was not the motion of the individual body parts, but the horizontal motion of the body’s centre of gravity.
To test their theory, the researchers created a computer simulation that could accurately simulate standing balance and muscle reactions to balance disturbances by focusing on the relation of the subject’s center of gravity to the ground. Rather than predicting neural control patterns for the multitude of sensory information processed by the body to maintain balance, the team instead tracked a small set of signals related to the body’s control of its centre of gravity.
They determined that subjects who had impaired sensory information were slowly using new sensory pathways to track the motion of the body’s centre of gravity, compensating for the loss of information from the damaged sensory pathways. In effect, the subjects’ muscles were using different neural information to perform the same balance tasks, resulting in muscle activity patterns that looked “abnormal,” but that were actually similar to the predicted optimum.
The research team is now testing its center of gravity simulation with human subjects and a small robot with simulated muscles.
MEDICA.de; Source: Georgia Institute of Technology