Effect of paired-pulse stimulus parameters on the two phases of short interval intracortical inhibition in the quadriceps muscle group

Using the paired-pulse paradigm, transcranial magnetic stimulation (TMS) has revealed much about the human primary motor cortex (M1). A preceding subthreshold conditioning stimulus (CS) inhibits the excitability of the motor cortex, which is named short-interval intracortical inhibition (SICI). In contrast, facilitation is observed when the first pulse (S1) is followed by a second one at threshold (S2), named short-interval intracortical facilitation (SICF). SICI and SICF have been considered to be mediated by different neural circuits within M1, but more recent studies reported relations between them. In this study, we performed triple-pulse stimulation consisting of CS-S1-S2 to further explore putative interactions between these two effects. Three intensities of CS (80–120% of active motor threshold: AMT) and two intensities of S2 (120 and 140% AMT) were combined. The SICF in the paired-pulse paradigm exhibited clear facilitatory peaks at ISIs of 1.5 and 3 ms. The second peak at 3 ms was significantly suppressed by triple-pulse stimulation using 120% AMT CS, although the first peak was almost unaffected. Our present results obtained using triple-pulse stimulation suggest that each peak of SICF is differently modulated by different intensities of CS. The suppression of the second peak might be ascribed to the findings in the paired-pulse paradigm that CS mediates SICI by inhibiting later I waves such as I3 waves and that the second peak of SICF is most probably related to I3 waves. We propose that CS might inhibit the second peak of SICF at the interneurons responsible for I3 waves.

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Excitability of human motor and visual cortex before, during, and after hyperventilation

Journal of Applied Physiology ◽

10.1152/japplphysiol.00770.2006 ◽

2007 ◽

Vol 102 (1) ◽

pp. 406-411 ◽

Cited By ~ 22

Author(s):

Roland Sparing ◽

Manuel Dafotakis ◽

Dorothee Buelte ◽

Ingo G. Meister ◽

Johannes Noth

Keyword(s):

Visual Cortex ◽

Neuronal Excitability ◽

Short Interval ◽

Motor Evoked Potential ◽

Brain Structures ◽

Intracortical Inhibition ◽

Neuronal Circuits ◽

Paired Pulse ◽

Stimulus Response ◽

End Tidal

In humans, hyperventilation (HV) has various effects on systemic physiology and, in particular, on neuronal excitability and synaptic transmission. However, it is far from clear how the effects of HV are mediated at the cortical level. In this study we investigated the effects of HV-induced hypocapnia on primary motor (M1) and visual cortex (V1) excitability. We used 1) motor threshold (MT) and phosphene threshold (PT) and 2) stimulus-response (S-R) curves (i.e., recruitment curves) as measures of excitability. In the motor cortex, we additionally investigated 3) the intrinsic inhibitory and facilitatory neuronal circuits using a short-interval paired-pulse paradigm. Measurements were performed before, during, and after 10 min of HV (resulting in a minimum end-tidal Pco2 of 15 Torr). HV significantly increased motor-evoked potential (MEP) amplitudes, particularly at lower transcranial magnetic stimulation (TMS) intensities. Paired-pulse stimulation indicated that HV decreases intracortical inhibition (ICI) without changing intracortical facilitation. The results suggestthat low Pco2 levels modulate, in particular, the intrinsic neuronal circuits of ICI, which are largely mediated by neurons containing γ-aminobutyric acid. Modulation of MT probably resulted from alterations of Na+ channel conductances. A significant decrease of PT, together with higher intensity of phosphenes at low stimulus intensities, furthermore suggested that HV acts on the excitability of M1 and V1 in a comparable fashion. This finding implies that HV also affects other brain structures besides the corticospinal motor system. The further exploration of these physiological mechanisms may contribute to the understanding of the various HV-related clinical phenomenona.

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Two phases of short-interval intracortical inhibition

Experimental Brain Research ◽

10.1007/s00221-003-1502-9 ◽

2003 ◽

Vol 151 (3) ◽

pp. 330-337 ◽

Cited By ~ 156

Author(s):

Lailoma Roshan ◽

Guillermo O. Paradiso ◽

Robert Chen

Keyword(s):

Short Interval ◽

Intracortical Inhibition ◽

Two Phases

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Examining motor evoked potential amplitude and short‐interval intracortical inhibition on the up‐going and down‐going phases of a transcranial alternating current stimulation (tacs) imposed alpha oscillation

European Journal of Neuroscience ◽

10.1111/ejn.15124 ◽

2021 ◽

Author(s):

Ann‐Maree Vallence ◽

Kathryn Dansie ◽

Mitchell R. Goldsworthy ◽

Suzanne M. McAllister ◽

Ruiting Yang ◽

...

Keyword(s):

Evoked Potential ◽

Short Interval ◽

Motor Evoked Potential ◽

Intracortical Inhibition ◽

Alternating Current ◽

Potential Amplitude ◽

Alpha Oscillation ◽

Transcranial Alternating Current Stimulation

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Modulation of intracortical inhibition during physically performed and mentally simulated balance tasks

European Journal of Applied Physiology ◽

10.1007/s00421-020-04577-1 ◽

2021 ◽

Vol 121 (5) ◽

pp. 1379-1388

Author(s):

A. Mouthon ◽

J. Ruffieux ◽

W. Taube

Keyword(s):

Motor Evoked Potentials ◽

Action Observation ◽

Short Interval ◽

Intracortical Inhibition ◽

Mental Simulation ◽

Task Execution ◽

Postural Tasks ◽

Execution Condition ◽

The One ◽

Postural Task

Abstract Purpose Action observation (AO) during motor imagery (MI), so-called AO + MI, has been proposed as a new form of non-physical training, but the neural mechanisms involved remains largely unknown. Therefore, this study aimed to explore whether there were similarities in the modulation of short-interval intracortical inhibition (SICI) during execution and mental simulation of postural tasks, and if there was a difference in modulation of SICI between AO + MI and AO alone. Method 21 young adults (mean ± SD = 24 ± 6.3 years) were asked to either passively observe (AO) or imagine while observing (AO + MI) or physically perform a stable and an unstable standing task, while motor evoked potentials and SICI were assessed in the soleus muscle. Result SICI results showed a modulation by condition (F2,40 = 6.42, p = 0.009) with less SICI in the execution condition compared to the AO + MI (p = 0.009) and AO (p = 0.002) condition. Moreover, switching from the stable to the unstable stance condition reduced significantly SICI (F1,20 = 8.34, p = 0.009) during both, physically performed (− 38.5%; p = 0.03) and mentally simulated balance (− 10%, p < 0.001, AO + MI and AO taken together). Conclusion The data demonstrate that SICI is reduced when switching from a stable to a more unstable standing task during both real task execution and mental simulation. Therefore, our results strengthen and further support the existence of similarities between executed and mentally simulated actions by showing that not only corticospinal excitability is similarly modulated but also SICI. This proposes that the activity of the inhibitory cortical network during mental simulation of balance tasks resembles the one during physical postural task execution.

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Remote muscle priming anodal transcranial direct current stimulation attenuates short interval intracortical inhibition and increases time to task failure of a constant workload cycling exercise

Experimental Brain Research ◽

10.1007/s00221-021-06103-x ◽

2021 ◽

Author(s):

Simranjit K. Sidhu

Keyword(s):

Direct Current ◽

Transcranial Direct Current Stimulation ◽

Short Interval ◽

Intracortical Inhibition ◽

Cycling Exercise ◽

Task Failure ◽

Direct Current Stimulation

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The Functional Role of Response Suppression during an Urge to Relieve Pain

Journal of Cognitive Neuroscience ◽

10.1162/jocn_a_01423 ◽

2019 ◽

Vol 31 (9) ◽

pp. 1404-1421

Author(s):

Kelsey K. Sundby ◽

Johanna Wagner ◽

Adam R. Aron

Keyword(s):

Short Interval ◽

Intracortical Inhibition ◽

Gabaergic Interneuron ◽

Response Suppression ◽

Active Response ◽

Relieve Pain ◽

Clinical Disorders ◽

Functional Relevance ◽

Interneuron Activity

Being in the state of having both a strong impulse to act and a simultaneous need to withhold is commonly described as an “urge.” Although urges are part of everyday life and also important to several clinical disorders, the components of urge are poorly understood. It has been conjectured that withholding an action during urge involves active response suppression. We tested that idea by designing an urge paradigm that required participants to resist an impulse to press a button and gain relief from heat (one hand was poised to press while the other arm had heat stimulation). We first used paired-pulse TMS over motor cortex (M1) to measure corticospinal excitability of the hand that could press for relief, while participants withheld movement. We observed increased short-interval intracortical inhibition, an index of M1 GABAergic interneuron activity that was maintained across seconds and specific to the task-relevant finger. A second experiment replicated this. We next used EEG to better “image” putative cortical signatures of motor suppression and pain. We found increased sensorimotor beta contralateral to the task-relevant hand while participants withheld the movement during heat. We interpret this as further evidence of a motor suppressive process. Additionally, there was beta desynchronization contralateral to the arm with heat, which could reflect a pain signature. Strikingly, participants who “suppressed” more exhibited less of a putative “pain” response. We speculate that, during urge, a suppressive state may have functional relevance for both resisting a prohibited action and for mitigating discomfort.

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