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Table 1 Description of TMS protocols assessing M1 activity

From: Non-invasive brain stimulation as a tool to study cerebellar-M1 interactions in humans

Measures Protocol Outcome
RMT Smallest intensity of the SMO required to elicit MEPS of ≥ 50 μV Synaptic excitability in M1 Excitability of axons in M1 activated by TMS
MEP Average amplitude of MEPs using a fixed SMO (1 mV intensity, or percentage of RMT) or multiple intensities (recruitment curve: e.g. 100 to 150 % of RMT) Global corticospinal excitability
CBI Dual-coil: suprathreshold CS to the cerebellar cortex 5–7 ms before a suprathreshold TS over the contralateral M1 Excitability of the DTC pathway
SICI Paired-pulse: subthreshold CS 2–3 ms before a suprathreshold TS over M1 Short duration GABAa-ergic inhibition
LICI Paired-pulse: suprathreshold CS 100–200 ms before a suprathreshold TS over M1 Long duration GABAb-ergic inhibition
CSP Suprathreshold TS applied during slight tonic contraction of target muscle Long duration GABAb-ergic inhibition
SICF Paired-pulse: suprathreshold CS 1.1–1.5, 2.3–2.9 and 4.1–4.4 ms before a subthreshold TS over M1 Excitability of cortical interneurons and I-waves generation
ICF Paired-pulse: subthreshold CS 7–20 ms before a suprathreshold TS over M1 Cortical net facilitation involving glutamate
SAI Pairing of a median nerve electrical stimulation 20–25 ms before a suprathreshold TS over M1 Sensory afferent inhibition mediated by Ach and GABAa-ergic inhibition
LAI Pairing of a median nerve electrical stimulation 200 ms before a TS over M1 Sensory afferent inhibition (pathway unknown)
  1. ACh acetylcholine, CBI cerebellar brain inhibition, CS conditioning stimulus, CSP cortical silent period, DTC dentate-thalamo-cortical pathway, GABA gamma-aminobutyric acid, RMT resting motor threshold, LAI long latency afferent inhibition, LICI long interval intracortical inhibition, MEP motor evoked potential, SAI short latency afferent inhibition, SICI short interval intracortical inhibition, SICF short interval intracortical facilitation, ICF intracortical facilitation, SMO stimulator output intensity, TS test stimulus