Effect of paired-pulse electrical stimulation on the activity of cortical circuits

Objective: we investigated the transient effect of short-duration paired-pulse electrical stimulation (ppes) on corticospinal excitability and the after-effect of long-duration ppes on excitability,short-latency afferent inhibition (sai),and afferent facilitation (af). methods: a total of 28 healthy subjects participated in two different experiments. in experiment 1,motor-evoked potentials (meps) were measured in the abductor pollicis brevis (apb) and abductor digiti minimi (adm) muscles before and immediately after short-duration ppes (5 s) at various inter-pulse intervals (2,3,4,5,6,7,10,15,20,and 30 ms). in experiment 2,meps,sai,and af were measured before,immediately,and 20 and 40 min after long-duration ppes (20 min,inter-pulse interval of 5 and 15 ms) and peripheral electrical stimulation (20 min,10 and 20 hz). results: short-duration ppes with inter-pulse intervals of 5 and 20 ms significantly increased mep measured in apb but not in adm. long-duration ppes with an inter-pulse interval of 5 ms significantly decreased sai but not meps in apb. in contrast,long-duration ppes did not affect adm. conclusion: the afferent inputs induced by ppes-5 ms were effective for transiently increasing mep and sustaining sai reduction. © 2015 saito,onishi,miyaguchi,kotan and fujimoto.