FC46.1 Interactions between short interval intracortical facilitation and short interval intracortical inhibition in the human motor cortex

2006 ◽  
Vol 117 ◽  
pp. 110
Author(s):  
A. Wagle ◽  
C. Gunraj ◽  
R. Chen
Keyword(s):  
Motor Cortex ◽  
Short Interval ◽  
Intracortical Inhibition ◽  
Intracortical Facilitation ◽  
Human Motor Cortex ◽  
Human Motor

Inhibitory and Disinhibitory Effects on I-Wave Facilitation in Motor Cortex

2011 ◽  
Vol 105 (1) ◽  
pp. 100-106 ◽  
Author(s):  
R.F.H. Cash ◽  
U. Ziemann ◽  
G. W. Thickbroom
Keyword(s):  
Motor Cortex ◽  
Short Interval ◽  
Intracortical Inhibition ◽  
Pulse Interval ◽  
Onset Latency ◽  
Intracortical Facilitation ◽  
Human Motor Cortex ◽  
Human Motor ◽  
Sufficient Strength ◽  
Inhibitory Regulation

A suprathreshold pulse of transcranial magnetic stimulation (TMS) delivered to human motor cortex results in a period of long-interval intracortical inhibition (LICI) followed by a briefer period of disinhibition (late cortical disinhibition [LCD]). Short-interval intracortical facilitation (SICF) is mediated by excitatory networks in the motor cortex responsible for the generation of the indirect (I-) wave volleys that are evoked by TMS at a periodicity of about 1.5 ms. Because the excitatory synaptic network responsible for SICF undergoes inhibitory regulation, we hypothesized that SICF will be modulated during periods of inhibition and disinhibition. In particular we were interested to know whether SICF was up-regulated during disinhibition, implying an increase in excitatory synaptic efficacy. We measured SICF, at a paired-pulse interval of 1.5 ms, at various times (100–300 ms) after a suprathreshold priming stimulus (PS) of sufficient strength to evoke LICI and LCD. We found that the strength of SICF was normal during LICI, but was increased during LCD by an average of 64%. SICF onset latency was reduced by one I-wave interval during LCD and was delayed by one I-wave interval during LICI. We conclude that disinhibition, rather than inhibition, modulates the excitatory neuronal networks that underlie SICF, whereas the I-wave targeted is modified by the presence of both inhibition and disinhibition and that there is therefore a dissociation between the strength and site of SICF interaction. The increase in SICF during disinhibition further indicates that this is a promising period to investigate or modulate excitatory synaptic networks while they are less constrained by ongoing levels of inhibition.

scholarly journals Two forms of short-interval intracortical inhibition in human motor cortex

2021 ◽  
Author(s):  
Po-Yu Fong ◽  
Danny Spampinato ◽  
Lorenzo Rocchi ◽  
Ricci Hannah ◽  
Yinghui Teng ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Short Interval ◽  
Intracortical Inhibition ◽  
Human Motor Cortex ◽  
Human Motor

Late Cortical Disinhibition in Human Motor Cortex: A Triple-Pulse Transcranial Magnetic Stimulation Study

2010 ◽  
Vol 103 (1) ◽  
pp. 511-518 ◽  
Author(s):  
R. F. H. Cash ◽  
U. Ziemann ◽  
K. Murray ◽  
G. W. Thickbroom
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Motor Cortex ◽  
Magnetic Stimulation ◽  
Short Interval ◽  
Motor Evoked Potential ◽  
Silent Period ◽  
Intracortical Inhibition ◽  
Human Motor Cortex ◽  
Acid Type ◽  
Human Motor

In human motor cortex transcranial magnetic stimulation (TMS) has been used to identify short-interval intracortical inhibition (SICI) corresponding to γ-aminobutyric acid type A (GABAA) effects and long-interval intracortical inhibition (LICI) and the cortical silent period (SP) corresponding to postsynaptic GABAB effects. Presynaptic GABAB effects, corresponding to disinhibition, can also be identified with TMS and have been shown to be acting during LICI by measuring SICI after a suprathreshold priming stimulus (PS). The duration of disinhibition is not certain and, guided by studies in experimental preparations, we hypothesized that it may be longer-lasting than postsynaptic inhibition, leading to a period of late cortical disinhibition and consequently a net increase in corticospinal excitability. We tested this first by measuring the motor-evoked potential (MEP) to a test stimulus (TS), delivered after a PS at interpulse intervals (IPIs) ≤300 ms that encompassed the period of PS-induced LICI and its aftermath. MEP amplitude was initially decreased, but then increased at IPIs of 190–210 ms, reaching 160 ± 17% of baseline 200 ms after PS ( P < 0.05). SP duration was 181 ± 5 ms. A second experiment established that the onset of the later period of increased excitability correlated with PS intensity ( r2 = 0.99) and with the duration of the SP ( r2 = 0.99). The third and main experiment demonstrated that SICI was significantly reduced in strength at all IPIs ≤220 ms after PS. We conclude that TMS-induced LICI is associated with a period of disinhibition that is at first masked by LICI, but that outlasts LICI and gives rise to a period during which disinhibition predominates and net excitability is raised. Identification of this late period of disinhibition in human motor cortex may provide an opportunity to explore or modulate the behavior of excitatory networks at a time when inhibitory effects are restrained.

scholarly journals Physiological Processes Underlying Short Interval Intracortical Facilitation in the Human Motor Cortex

2018 ◽  
Vol 12 ◽  
Author(s):  
Mehdi A. J. Van den Bos ◽  
Parvathi Menon ◽  
James Howells ◽  
Nimeshan Geevasinga ◽  
Matthew C. Kiernan ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Short Interval ◽  
Intracortical Facilitation ◽  
Human Motor Cortex ◽  
Physiological Processes ◽  
Human Motor
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