A neural network model of force control based on the size principle of motor unit

A neural network model consisting of a single motor cortex output cell, alpha -motoneurons, Renshaw cells, and muscle units is presented. The firing rates of alpha -motoneurons obtained from the model at different levels of muscle force closely agree with those measured in human muscles. The isometric force of the model increases almost linearly with the discharge frequencies of the motor cortex output cell, in much the same fashion as has been observed in monkeys. The effects of the size and number of alpha -motoneurons in a motoneuron pool and of inhomogeneous inhibitory actions via Renshaw cells on the behavior of motor units are investigated.<>