Short-interval intracortical inhibition as a function of inter-stimulus interval: Three methods compared

BackgroundShort-interval intracortical inhibition (SICI), as measured by threshold-tracking a function of inter-stimulus interval (ISI), has been proposed useful biomarker for amyotrophic lateral sclerosis (ALS), but its relationship to conventional amplitude measurements not established.MethodsSerial tracking SICI at increasing ISIs from 1 7 ms (T-SICIs) was compared in 50 healthy control subjects with the same tracked parallel (T-SICIp), and (A-SICI). For T-SICIp A-SICI, pairs conditioning test stimuli different were pseudo-randomised interspersed test-alone given regular intervals. Thresholds estimated regression log peak-to-peak on stimulus.ResultsT-SICIp A-SICI closely related: ten-fold reduction corresponding an approximately 18% increase threshold. Threshold increases greater T-SICIs than 3.5–5 (P < 0.001). This divergence depended initial settings whether progressively increased or decreased, attributed limitations serial protocol. variability between greatest estimates least only revealed significant decline age.ConclusionsThe protocol did accurately show dependence ISI. Randomising gives measures, thresholds measuring measurements. suggested that may be most sensitive loss inhibition.