Figure 3. The effects of cutaneous inputs on the Ia presynaptic inhibition induced by median nerve stimulation.
The higher the motor unit response probability measured while the radial nerve was being stimulated alone, the stronger its response probability assessed from the whole peak (A) or from the first 0.5 ms (B) was found to be depressed while applying stimulation to the median nerve, both during wrist extension without (▪, dotted line) and with (▵, continuous line) cutaneous stimulation. The higher Y-intercept suggests that the presynaptic inhibition presumed to be evoked by the median nerve stimulation may be relieved by the tonic cutaneous inputs. C and D, mean changes in the response probability in trials during which the median nerve was stimulated and cutaneous stimulation was applied () or not (□). Applying cutaneous stimulation was found to reduce the presumed presynaptic inhibition estimated both from the whole peak (C) and from the monosynaptic components (D).