Modeling of Impulse Activity of Afferent Fibers of Antagonist Muscles during Transcutaneous Electrical Stimulation of the Spinal Cord During Walking.

The article describes the results of studies on the impulse activity of various groups of afferent fibers and EMG patterns of lower leg antagonist muscles when walking without, during, and after transcutaneous electrical stimulation of the dorsal roots of the lower thoracic spinal cord of a person. Using a mathematical model based on the prediction of the triggering of muscle spindles, variability in the manifestation of impulse activity of various afferents of the tibialis anterior (TA) and gastrocnemius medialis (GM) muscle when walking under different experimental conditions is shown. It was found that walking on a movable treadmill tape in the absence of spinal cord stimulation was accompanied by strong impulse activity of afferents of I (Ia and Ib) and II groups of GM and increased excitability of its motorneuron pool and weakening of afferent activity and excitability of TA. On the contrary, electrical stimulation of the spinal cord during walking caused strong impulsive activity of group II of TA afferents and moderate in GM, while the activity of Ia fibers in TA and GM decreased to moderate impulsivity, Ib afferents of the same muscles had the weakest activity, and the excitability of the GM motor neuron pool was greater than TA. During the postactivation period, walking was accompanied by increased impulses of afferent fibers of group Ib and II of GM, weakening of afferent flows of Ib of TA and Ia afferents of GM, but along with this, afferent signals of group Ia and II to the motor neuron nucleus of TA decreased to moderate impulses, and excitability of the motor neuron pool of GM was higher than TA. The supposed reflex mechanisms of locomotion regulation are discussed on the basis of well-known phenomena associated with the interaction of various afferent inputs to the spinal cord neuronal apparatus in the system of lower leg antagonist muscles. [ABSTRACT FROM AUTHOR]