[A method for studying spinal reflex arcs among muscles in the human upper limb: a post-stimulus time-histogram technique].

A post-stimulus time-histogram (PSTH) technique has been used for studying spinal reflex arcs in humans. In the PSTH technique, effects of the reflex arcs on the motoneuron excitability are examined by analyzing changes in firing probabilities of a motor unit after conditioning stimuli to afferent fibers. Recent studies with the PSTH technique have demonstrated reflex arcs mediated by low threshold muscle afferent fibers (group I afferents) among muscles in the human upper limb. The results have shown several differences of the reflex arcs between the human upper limb and animal forelimb. This paper has described the PSTH technique. Comparisons of the reflex arcs between humans and animals have been also described.