Table 2.

Paired-pulse transcranial magnetic stimulation techniques

	Paired pulse
	SICI	ICF	LICI	IHI	SAI	LAI	CMCT
CNS measure	Intracortical inhibition	Intracortical facilitation	Intracortical inhibition	Interhemispheric inhibition	Sensorimotor integration	Sensorimotor integration	Cortical output latency
Neural circuitry	GABAA receptor-mediated	Glutamate, other mechanisms	GABAB receptor-mediated	SIHI: Unknown LIHI: GABAB-mediated	ACh, unknown	Unknown	Cortical and peripheral conduction time
ISI (msec)	1–6 msec	10–15 msec	50–200 msec	SIHI (8–19 msec)	18–21 msec	200 msec	NA
				LI HI (20–50 msec)
Protocol	Subthreshold CS followed by a suprathreshold TS	Subthreshold CS followed by a suprathreshold TS	Suprathreshold CS and TS	Suprathreshold CS over one M1 followed by a suprathreshold TS over contralateral M1	Peripheral nerve stimulation followed by a single TMS pulse	Peripheral nerve stimulation followed by a single TMS pulse	Spinal motor neuron to muscle latency minus cortex to muscle latency

Abbreviations: SICI, short-interval intracortical inhibition; ICF, intracortical facilitation; LICI, long-interval intracortical inhibition; II—II, interhemispheric inhibition; SAI, short-afferent inhibition; LAI, long-afferent inhibition; CMCT, central motor conduction time; GABA, gamma-aminobutyric acid; SIHI, short-latency interhemispheric inhibition; LI HI, long-latency interhemispheric inhibition; ACh, acetylcholine; CS, conditioning stimulus; TS, test stimulus; M I, primary motor cortex; TMS, transcranial magnetic stimulation; ISI, interstimulus interval; CNS, central nervous system; NA, not applicable.