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

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.

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Short-term reduction of intracortical inhibition in the human motor cortex induced by repetitive transcranial magnetic stimulation

Experimental Brain Research ◽

10.1007/s00221-002-1223-5 ◽

2002 ◽

Vol 147 (1) ◽

pp. 108-113 ◽

Cited By ~ 91

Author(s):

V. Di Lazzaro ◽

Oliviero A. ◽

Mazzone P. ◽

Pilato F. ◽

Saturno E. ◽

...

Keyword(s):

Transcranial Magnetic Stimulation ◽

Motor Cortex ◽

Magnetic Stimulation ◽

Repetitive Transcranial Magnetic Stimulation ◽

Intracortical Inhibition ◽

Short Term ◽

Human Motor Cortex ◽

Human Motor

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Spinal and supraspinal mechanisms contribute to the silent period in the contracting soleus muscle after transcranial magnetic stimulation of human motor cortex

Neuroscience Letters ◽

10.1016/0304-3940(93)90464-v ◽

1993 ◽

Vol 156 (1-2) ◽

pp. 167-171 ◽

Cited By ~ 134

Author(s):

Ulf Ziemann ◽

Johannes Netz ◽

Andrea Szelényi ◽

Volker Hömberg

Keyword(s):

Transcranial Magnetic Stimulation ◽

Motor Cortex ◽

Soleus Muscle ◽

Magnetic Stimulation ◽

Silent Period ◽

Human Motor Cortex ◽

Human Motor ◽

Stimulation Of

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Reorganisation in human motor cortex

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y95-032 ◽

1995 ◽

Vol 73 (2) ◽

pp. 218-222 ◽

Cited By ~ 88

Author(s):

M. C. Ridding ◽

J. C Rothwell

Keyword(s):

Transcranial Magnetic Stimulation ◽

Motor Cortex ◽

Magnetic Stimulation ◽

Voluntary Contraction ◽

Short Latency ◽

Human Motor Cortex ◽

Amputation Stump ◽

Human Motor

Transcranial magnetic stimulation over the motor cortex was used to construct a map of the effective sites on the scalp from which short-latency electromyogram responses could be evoked in muscles proximal to either an amputation stump (two subjects) or an ischemically anesthetized forearm (two subjects). At rest, the maps were larger and the responses bigger when stimulating contralateral to the amputated arm or after anesthesia than they were in the intact arm or before anesthesia. However, this difference disappeared when the maps were constructed during a small tonic voluntary contraction of the target muscle. We conclude that reorganisation of the corticospinal projection to a muscle at rest may no longer be present during activity. If so, this calls into question the possible functional benefits of such reorganisation in the control of movement after peripheral damage.Key words: motor cortex, magnetic stimulation, amputation, ischemia.

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Neuroplasticity Changes on Human Motor Cortex Induced by Acupuncture Therapy: A Preliminary Study

Neural Plasticity ◽

10.1155/2017/4716792 ◽

2017 ◽

Vol 2017 ◽

pp. 1-8 ◽

Cited By ~ 10

Author(s):

Yi Yang ◽

Ines Eisner ◽

Siqi Chen ◽

Shaosong Wang ◽

Fan Zhang ◽

...

Keyword(s):

Transcranial Magnetic Stimulation ◽

Acupuncture Therapy ◽

Motor Cortex ◽

Magnetic Stimulation ◽

Primary Motor Cortex ◽

Motor Evoked Potential ◽

Interhemispheric Inhibition ◽

Human Motor Cortex ◽

Interhemispheric Competition ◽

Resting Motor Threshold

While neuroplasticity changes measured by transcranial magnetic stimulation have been proved to be highly correlated to motor recovery and have been tested in various forms of interventions, it has not been applied to investigate the neurophysiologic mechanism of acupuncture therapy. The aim of this study is to investigate neuroplasticity changes induced by a single session of acupuncture therapy in healthy adults, regarding the excitability change on bilateral primary motor cortex and interhemispheric inhibition. Ten subjects took a 30-minute acupuncture therapy and the same length relaxing phase in separate days. Transcranial magnetic stimulation measures, including resting motor threshold, amplitudes of motor-evoked potential, and interhemispheric inhibition, were assessed before and 10 minutes after intervention. Acupuncture treatment showed significant changes on potential amplitude from both ipsilateral and contralateral hemispheres to acupuncture compared to baseline. Also, interhemispheric inhibition from the contralateral motor cortex to the opposite showed a significant decline. The results indicated that corticomotoneuronal excitability and interhemispheric competition could be modulated by acupuncture therapy on healthy subjects. The following question about whether these changes will be observed in the same way on stroke patients and whether they correlate with the therapeutic effect on movement need to be answered by following studies. This trial is registered with ISRCTN13074245.

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Fatigue-induced changes in short-interval intracortical inhibition and the silent period with stimulus intensities evoking maximal versus submaximal responses

Journal of Applied Physiology ◽

10.1152/japplphysiol.00282.2020 ◽

2020 ◽

Vol 129 (2) ◽

pp. 205-217

Author(s):

Callum G. Brownstein ◽

Loïc Espeit ◽

Nicolas Royer ◽

Thomas Lapole ◽

Guillaume Y. Millet

Keyword(s):

Transcranial Magnetic Stimulation ◽

Magnetic Stimulation ◽

Short Interval ◽

Conditioning Stimulus ◽

Silent Period ◽

Single Pulse ◽

Intracortical Inhibition ◽

Fatiguing Exercise ◽

Induced Changes

This study compared the change in silent period (SP) and short-interval intracortical inhibition (SICI) with conditioning stimulus and single-pulse transcranial magnetic stimulation (TMS) intensities (for SICI and SP, respectively) eliciting maximal and submaximal SICI and SP during fatiguing exercise. The results showed that changes in SICI were only detectable with intensities evoking maximal responses, with no difference between intensities for SP. These findings highlight the importance of maximizing SICI with appropriate intensities before measuring SICI during fatiguing exercise.

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