Effect of desynchronized inputs on compound sensory and muscle action potentials

Abstract

Abstract Stimulation of the second (S 1 ) or third (S 2 ) digit elicits a median sensory potential at the wrist. Similarly, a shock applied to the median ( S m ) or ulnar ( S u ) nerve at the wrist evokes a sensory potential of the fourth digit and a muscle potential over the thenar eminence. Hence, a concomitant application of S 1 and S 2 or S m and S u with varying interstimulus intervals simulates the effect of desynchronized inputs. In 10 hands, a shift in latency on the order of 1 msec between S 1 and S 2 or S m and S u caused a major reduction in sensory potential by as much as 30–40% but little change in muscle action potential. A latency difference slightly less than one‐half the total duration of unit discharge maximized the phase cancellation between the two components and consequently the loss of area under the wave‐form.