Using an experimental apparatus he and his students created in UD's Human Performance Lab, Knight has been examining muscular force on a very small scale in the index finger, specifically, the first dorsal interosseous muscle. Located between the index finger and the thumb, this muscle contains 120 "motor units"--in other words, 120 individual neurons, or nerve cells, and the muscle fibers they activate.
"It's a relatively simple muscle, so you get to see more of a one-to-one relationship between the activity of the neurons and the resulting muscular force," Knight said.
Twenty-three subjects, ranging from 18 to 88 years of age, participated in Knight's recent study.
In a virtually painless procedure, a small needle-like electrode with four tiny wires was embedded in the muscle of an index finger of each subject. The electrode was hooked up to a computer to record the electrical impulses as they travel from neurons to the muscle fibers.
As the index finger was held steady in a small harness, each subject was asked to use the finger to follow the outline of a sinusoidal curve, with its peaks and valleys, on a computer screen.
"More force--which is indicated by a corresponding higher firing rate of neurons--is exerted just before you begin the upturn toward one peak and then it eases off again in the downturn toward a valley," Knight noted.
Once recordings were completed at one site in the muscle, the electrode was repositioned to sample from other motor units within the muscle.
Knight and graduate student Dhiraj Poojari and undergraduate researchers Maria Bellumori and Christopher Martens then analyzed the firing-rate data for frequency and amplitude in a tedious process that Knight hopes to automate in the future through the ongoing development of a software program that will help sort out the bang-bang-like "doublets," the brief
Source:University of Delaware