Recently, 2 physiologically distinct phases of short-interval intracortical inhibition (SICI) have been identified, a larger phase at interstimulus interval (ISI) 3 ms and a smaller phase at ISI 1 ms. While the former is mediated by synaptic processes, the mechanisms underlying the first phase of SICI remain a matter of debate. Separately, it is known that fatiguing hand exercise reduces SICI, ...

Peripheral nerve stimulation inhibits the motor cortex, and the process has been termed short-latency afferent inhibition (SAI) at interstimulus intervals (ISIs) of ∼20 ms. The objective of the present study was to test how SAI interacts with short-interval intracortical inhibition (SICI) under different stimulation conditions. We studied 20 healthy volunteers. Surface electromyogram was record...

UNLABELLED Short-interval intracortical inhibition (SICI) of the primary motor cortex (M1) appears to play a significant role in skill acquisition. Consequently, it is of interest to find out which factors cause modulation of SICI. PURPOSE To establish if visual feedback and force requirements influence SICI. METHODS SICI was assessed from 10 healthy adults (5 males and 5 females aged betwe...

Performance of a unimanual hand motor task results in functional changes in both primary motor cortices (M1(ipsilateral) and M1(contralateral)). The neuronal mechanisms controlling the corticospinal output originated in M1(ipsilateral) and the resting hand during a unimanual task remain unclear. Here, we assessed functional changes within M1(ipsilateral) and in interhemispheric inhibition (IHI)...

The sensorimotor cortices of the human brain contain intracortical inhibitory circuits that influence the neural output to muscles. Intracortical circuits of short and long-interval intracortical inhibition (SICI and LICI) can be probed using paired-pulse TMS paradigms while recording activity from the muscles. We recently identified changes in SICI and LICI within the motor cortex in individua...

The split-hand phenomenon, a specific feature of amyotrophic lateral sclerosis (ALS), refers to preferential wasting of abductor pollicis brevis (APB) and first dorsal interosseous (FDI) with relative preservation of abductor digiti minimi (ADM). The pathophysiological mechanisms underlying the split-hand phenomenon remain elusive and resolution of this issue would provide unique insights into ...