Response preparation involves a release of intracortical inhibition in task-irrelevant muscles

AbstractAction preparation involves widespread modulation of motor system excitability, but the precise mechanisms are unknown. In this study, we investigated whether intracortical inhibition changes in task-irrelevant muscle representations during action preparation. We used transcranial magnetic stimulation (TMS) combined with electromyography in healthy human adults to measure motor evoked potentials (MEPs) and cortical silent periods (CSPs) in task-irrelevant muscles during the preparatory period of simple delayed response tasks. In Experiment 1, participants responded with the left-index finger in one task condition and the right-index finger in another task condition, while MEPs and CSPs were measured from the contralateral non-responding and tonically contracted index finger. During Experiment 2, participants responded with the right pinky finger while MEPs and CSPs were measured from the tonically contracted left-index finger. In both experiments, MEPs and CSPs were compared between the task preparatory period and a resting intertrial baseline. The CSP duration during response preparation decreased from baseline in every case. A laterality difference was also observed in Experiment 1, with a greater CSP reduction during the preparation of left finger responses compared to right finger responses. MEP amplitudes showed no modulation during movement preparation in any of the three response conditions. These findings indicate cortical inhibition associated with task-irrelevant muscles is transiently released during action preparation and implicate a novel mechanism for the controlled and coordinated release of motor cortex inhibition.New & NoteworthyIn this study we observed the first evidence of a release of intracortical inhibition in task-irrelevant muscle representations during response preparation. We applied transcranial magnetic stimulation to elicit cortical silent periods in task-irrelevant muscles during response preparation and observed a consistent decrease in the silent period duration relative to a resting baseline. These findings address the question of whether cortical mechanisms underlie widespread modulation in motor excitability during response preparation.

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Response preparation involves a release of intracortical inhibition in task-irrelevant muscles

Journal of Neurophysiology ◽

10.1152/jn.00390.2020 ◽

2020 ◽

Author(s):

Isaac Nathaniel Gomez ◽

Kara Ormiston ◽

Ian Greenhouse

Keyword(s):

Index Finger ◽

Intracortical Inhibition ◽

Left Index Finger ◽

Delayed Response ◽

Task Condition ◽

Response Preparation ◽

Preparatory Period ◽

Action Preparation ◽

The Right ◽

Task Irrelevant

Action preparation involves widespread modulation of motor system excitability, but the precise mechanisms are unknown. In this study, we investigated whether intracortical inhibition changes in task-irrelevant muscle representations during action preparation. We used transcranial magnetic stimulation (TMS) combined with electromyography in healthy human adults to measure motor evoked potentials (MEPs) and cortical silent periods (CSPs) in task-irrelevant muscles during the preparatory period of simple delayed response tasks. In Experiment 1, participants responded with the left-index finger in one task condition and the right-index finger in another task condition, while MEPs and CSPs were measured from the contralateral non-responding and tonically contracted index finger. During Experiment 2, participants responded with the right pinky finger while MEPs and CSPs were measured from the tonically contracted left-index finger. In both experiments, MEPs and CSPs were compared between the task preparatory period and a resting intertrial baseline. The CSP duration during response preparation decreased from baseline in every case. A laterality difference was also observed in Experiment 1, with a greater CSP reduction during the preparation of left finger responses compared to right finger responses. Despite reductions in CSP duration, consistent with a release of intracortical inhibition, MEP amplitudes were smaller during action preparation when accounting for background levels of muscle activity, consistent with earlier studies that reported decreased corticospinal excitability. These findings indicate intracortical inhibition associated with task-irrelevant muscles is transiently released during action preparation and implicate a novel mechanism for the controlled and coordinated release of motor cortex inhibition.

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Effect of Transcranial Magnetic Stimulation on Bimanual Movements

Journal of Neurophysiology ◽

10.1152/jn.01063.2003 ◽

2005 ◽

Vol 93 (1) ◽

pp. 53-63 ◽

Cited By ~ 19

Author(s):

Jen-Tse Chen ◽

Yung-Yang Lin ◽

Din-E Shan ◽

Zin-An Wu ◽

Mark Hallett ◽

...

Keyword(s):

Transcranial Magnetic Stimulation ◽

Motor Cortex ◽

Left Hemisphere ◽

Magnetic Stimulation ◽

Normal Subjects ◽

Left Index Finger ◽

Rhythmic Movements ◽

Bimanual Movements ◽

Ipsilateral Stimulation ◽

The Right

Transcranial magnetic stimulation (TMS) of the motor cortex can interrupt voluntary contralateral rhythmic limb movements. Using the method of “resetting index” (RI), our study investigated the TMS effect on different types of bimanual movements. Six normal subjects participated. For unimanual movement, each subject tapped either the right or left index finger at a comfortable rate. For bimanual movement, index fingers of both hands tapped in the same (in-phase) direction or in the opposite (antiphase) direction. TMS was applied to each hemisphere separately at various intensities from 0.5 to 1.5 times motor threshold (MT). TMS interruption of rhythm was quantified by RI. For the unimanual movements, TMS disrupted both contralateral and ipsilateral rhythmic hand movements, although the effect was much less in the ipsilateral hand. For the bimanual in-phase task, TMS could simultaneously reset the rhythmic movements of both hands, but the effect on the contralateral hand was less and the effect on the ipsilateral hand was more compared with the unimanual tasks. Similar effects were seen from right and left hemisphere stimulation. TMS had little effect on the bimanual antiphase task. The equal effect of right and left hemisphere stimulation indicates that neither motor cortex is dominant for simple bimanual in-phase movement. The smaller influence of contralateral stimulation and the greater effect of ipsilateral stimulation during bimanual in-phase movement compared with unimanual movement suggest hemispheric coupling. The antiphase movements were resistant to TMS disruption, and this suggests that control of rhythm differs in the 2 tasks. TMS produced a transient asynchrony of movements on the 2 sides, indicating that both motor cortices might be downstream of the clocking command or that the clocking is a consequence of the 2 hemispheres communicating equally with each other.

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Task-related changes in intracortical inhibition assessed with paired- and triple-pulse transcranial magnetic stimulation

Journal of Neurophysiology ◽

10.1152/jn.00651.2014 ◽

2015 ◽

Vol 113 (5) ◽

pp. 1470-1479 ◽

Cited By ~ 12

Author(s):

George M. Opie ◽

Michael C. Ridding ◽

John G. Semmler

Keyword(s):

Transcranial Magnetic Stimulation ◽

Motor Cortex ◽

Magnetic Stimulation ◽

Muscle Activation ◽

Primary Motor Cortex ◽

Index Finger ◽

Precision Grip ◽

Intracortical Inhibition ◽

Presynaptic Mechanisms ◽

First Dorsal Interosseous Muscle

Recent research has demonstrated a task-related modulation of postsynaptic intracortical inhibition within primary motor cortex for tasks requiring isolated (abduction) or synergistic (precision grip) muscle activation. The current study sought to investigate task-related changes in pre- and postsynaptic intracortical inhibition in motor cortex. In 13 young adults (22.5 ± 3.5 yr), paired-pulse transcranial magnetic stimulation (TMS) was used to measure short (SICI)- and long-interval intracortical inhibition (LICI) (i.e., postsynaptic motor cortex inhibition) in first dorsal interosseous muscle, and triple-pulse TMS was used to investigate changes in SICI-LICI interactions (i.e., presynaptic motor cortex inhibition). These measurements were obtained at rest and during muscle activation involving isolated abduction of the index finger and during a precision grip using the index finger and thumb. SICI was reduced during abduction and precision grip compared with rest, with greater reductions during precision grip. The modulation of LICI during muscle activation depended on the interstimulus interval (ISI; 100 and 150 ms) but was not different between abduction and precision grip. For triple-pulse TMS, SICI was reduced in the presence of LICI at both ISIs in resting muscle (reflecting presynaptic motor cortex inhibition) but was only modulated at the 150-ms ISI during index finger abduction. Results suggest that synergistic contractions are accompanied by greater reductions in postsynaptic motor cortex inhibition than isolated contractions, but the contribution of presynaptic mechanisms to this disinhibition is limited. Furthermore, timing-dependent variations in LICI provide additional evidence that measurements using different ISIs may not represent activation of the same cortical process.

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Unravelling the modulation of intracortical inhibition during motor imagery: An adaptive threshold-hunting study

10.1101/846931 ◽

2019 ◽

Author(s):

Cécilia Neige ◽

Dylan Rannaud Monany ◽

Cathy M. Stinear ◽

Winston D. Byblow ◽

Charalambos Papaxanthis ◽

...

Keyword(s):

Transcranial Magnetic Stimulation ◽

Motor Cortex ◽

Motor Imagery ◽

Magnetic Stimulation ◽

Primary Motor Cortex ◽

Short Interval ◽

Intracortical Inhibition ◽

Adaptive Threshold ◽

Mental Simulation ◽

The Right

AbstractMotor imagery (MI) is the mental simulation of an action without any apparent muscular contraction. By means of transcranial magnetic stimulation, few studies revealed a decrease of short-interval intracortical inhibition (SICI) within the primary motor cortex. However, this decrease is ambiguous, as one would expect greater inhibition during MI to prevent overt motor output. The current study investigated the extent of SICI modulation during MI through a methodological and a conceptual reconsideration of i) the importance of parameters to assess SICI (Exp.1) and ii) the inhibitory process within the primary motor cortex as an inherent feature of MI (Exp.2). Participants performed two tasks: 1) rest and 2) imagery of isometric abduction of the right index finger. Using transcranial magnetic stimulation, motor evoked potentials were elicited in the right first dorsal interosseous muscle. An adaptive threshold-hunting paradigm was used, where the stimulus intensity required to maintain a fixed motor evoked potential amplitude was quantified. To test SICI, we conditioned the test stimulus with a conditioning stimulus (CS) of different intensities. Results revealed an Intensity by Task interaction showing that SICI decreased during MI as compared to rest only for the higher CS intensity (Exp.1). At the lowest CS intensities, a Task main effect revealed that SICI increased during MI (Exp.2). SICI modulation during MI depends critically on the CS intensity. By optimising CS intensity, we have shown that SICI circuits may increase during MI, revealing a potential mechanism to prevent the production of a movement while the motor system is activated.HighlightsExcitatory and inhibitory neural processes interact during motor imagery, as the motor regions are activated but no movement is produced.The current study investigated the extent of short interval intracortical inhibition modulation (SICI) during motor imagery.When using optimal settings, SICI increased during motor imagery, likely to prevent the production of an overt movement.

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Parallel Regulation of Past, Present, and Future Actions During Sequencing

10.31234/osf.io/avxe3 ◽

2018 ◽

Author(s):

Lawrence P. Behmer ◽

Kelly J. Jantzen ◽

Matthew Crump

Keyword(s):

Transcranial Magnetic Stimulation ◽

Evoked Potentials ◽

Magnetic Stimulation ◽

Index Finger ◽

Motor Evoked Potentials ◽

Single Letter ◽

Sequence Production ◽

Inhibition Process ◽

The Right ◽

Parallel Action

Past, present, and future actions must be regulated online to produce sequences of actions, but the regulation process is not well understood because of measurement limitations. We provide the first direct tests of the parallel action regulation hypothesis during sequencing in humans. We used transcranial magnetic stimulation to probe the level of excitation for flexion of the right index finger during typing. Motor evoked potentials (MEPs) were recorded at the onset of typing 5-letter words and nonwords. A single letter typed by the right index finger varied across letter positions 1 to 5. MEP amplitude was largest for the upcoming action in the second position and decreased monotonically across future serial positions, suggesting a serial inhibition process regulates all future actions in parallel during sequencing. This is the most direct human evidence to date corroborating models of sequence production that assume parallel regulation of actions.

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Interhemispheric interactions between the right angular gyrus and the left motor cortex: a transcranial magnetic stimulation study

Journal of Neurophysiology ◽

10.1152/jn.00642.2020 ◽

2021 ◽

Author(s):

Julianne Baarbé ◽

Michael Vesia ◽

Matt Brown ◽

Karlo J. Lizarraga ◽

Carolyn A Gunraj ◽

...

Keyword(s):

Transcranial Magnetic Stimulation ◽

Motor Cortex ◽

Magnetic Stimulation ◽

Posterior Parietal Cortex ◽

Short Interval ◽

Intracortical Inhibition ◽

Angular Gyrus ◽

Posterior Parietal ◽

The Right ◽

Left Angular Gyrus

The interconnection of the angular gyrus of right posterior parietal cortex (PPC) and the left motor cortex (LM1) is essential for goal-directed hand movements. Previous work with transcranial magnetic stimulation (TMS) showed that right PPC stimulation increases LM1 excitability but right PPC followed by left PPC-LM1 stimulation (LPPC-LM1) inhibits LM1 corticospinal output compared to LPPC-LM1 alone. It is not clear if right PPC-mediated inhibition of LPPC-LM1 is due to inhibition of left PPC or to combined effects of right and left PPC stimulation on LM1 excitability. We used paired-pulse TMS to study the extent to which combined right and left PPC stimulation, targeting the angular gyri, influences LM1 excitability. We tested 16 healthy subjects in five paired-pulsed TMS experiments using MRI-guided neuronavigation to target the angular gyri within PPC. We tested the effects of different right angular gyrus (RAG) and LM1 stimulation intensities on the influence of RAG on LM1 and on influence of left angular gyrus (LAG) on LM1 (LAG-LM1). We then tested the effects of RAG and LAG stimulation on LM1 short-interval intracortical facilitation(SICF), short-interval intracortical inhibition(SICI) and long-interval intracortical inhibition(LICI). The results revealed that RAG facilitated LM1, inhibited SICF and inhibited LAG-LM1. Combined RAG-LAG stimulation did not affect SICI but increased LICI. These experiments suggest that RAG-mediated inhibition of LAG-LM1 is related to inhibition of early I-wave activity and enhancement of GABAB receptor-mediated inhibition in LM1. The influence of RAG on LM1 likely involves ipsilateral connections from LAG to LM1 and heterotopic connections from RAG to LM1.

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Single-Pulse Transcranial Magnetic Stimulation-Evoked Potential Amplitudes and Latencies in the Motor and Dorsolateral Prefrontal Cortex among Young, Older Healthy Participants, and Schizophrenia Patients

Journal of Personalized Medicine ◽

10.3390/jpm11010054 ◽

2021 ◽

Vol 11 (1) ◽

pp. 54

Author(s):

Yoshihiro Noda ◽

Mera S. Barr ◽

Reza Zomorrodi ◽

Robin F. H. Cash ◽

Pantelis Lioumis ◽

...

Keyword(s):

Prefrontal Cortex ◽

Transcranial Magnetic Stimulation ◽

Magnetic Stimulation ◽

Dorsolateral Prefrontal Cortex ◽

Evoked Potential ◽

Single Pulse ◽

Signal Propagation ◽

Lower Amplitude ◽

Dorsolateral Prefrontal ◽

The Right

Background: The combination of transcranial magnetic stimulation (TMS) with electroencephalography (EEG) allows for non-invasive investigation of cortical response and connectivity in human cortex. This study aimed to examine the amplitudes and latencies of each TMS-evoked potential (TEP) component induced by single-pulse TMS (spTMS) to the left motor (M1) and dorsolateral prefrontal cortex (DLPFC) among healthy young participants (YNG), older participants (OLD), and patients with schizophrenia (SCZ). Methods: We compared the spatiotemporal characteristics of TEPs induced by spTMS among the groups. Results: Compared to YNG, M1-spTMS induced lower amplitudes of N45 and P180 in OLD and a lower amplitude of P180 in SCZ, whereas the DLPFC-spTMS induced a lower N45 in OLD. Further, OLD demonstrated latency delays in P60 after M1-spTMS and in N45-P60 over the right central region after left DLPFC-spTMS, whereas SCZ demonstrated latency delays in N45-P60 over the midline and right central regions after DLPFC-spTMS. Conclusions: These findings suggest that inhibitory and excitatory mechanisms mediating TEPs may be altered in OLD and SCZ. The amplitude and latency changes of TEPs with spTMS may reflect underlying neurophysiological changes in OLD and SCZ, respectively. The spTMS administered to M1 and the DLPFC can probe cortical functions by examining TEPs. Thus, TMS-EEG can be used to study changes in cortical connectivity and signal propagation from healthy to pathological brains.

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Causal modulation of right hemisphere fronto-parietal phase synchrony with Transcranial Magnetic Stimulation during a conscious visual detection task

Scientific Reports ◽

10.1038/s41598-020-79812-y ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Chloé Stengel ◽

Marine Vernet ◽

Julià L. Amengual ◽

Antoni Valero-Cabré

Keyword(s):

Transcranial Magnetic Stimulation ◽

Visual Perception ◽

Frequency Band ◽

Magnetic Stimulation ◽

Visual Detection ◽

Detection Task ◽

Oscillatory Activity ◽

Top Down ◽

The Right ◽

High Beta

AbstractCorrelational evidence in non-human primates has reported increases of fronto-parietal high-beta (22–30 Hz) synchrony during the top-down allocation of visuo-spatial attention. But may inter-regional synchronization at this specific frequency band provide a causal mechanism by which top-down attentional processes facilitate conscious visual perception? To address this question, we analyzed electroencephalographic (EEG) signals from a group of healthy participants who performed a conscious visual detection task while we delivered brief (4 pulses) rhythmic (30 Hz) or random bursts of Transcranial Magnetic Stimulation (TMS) to the right Frontal Eye Field (FEF) prior to the onset of a lateralized target. We report increases of inter-regional synchronization in the high-beta band (25–35 Hz) between the electrode closest to the stimulated region (the right FEF) and right parietal EEG leads, and increases of local inter-trial coherence within the same frequency band over bilateral parietal EEG contacts, both driven by rhythmic but not random TMS patterns. Such increases were accompained by improvements of conscious visual sensitivity for left visual targets in the rhythmic but not the random TMS condition. These outcomes suggest that high-beta inter-regional synchrony can be modulated non-invasively and that high-beta oscillatory activity across the right dorsal fronto-parietal network may contribute to the facilitation of conscious visual perception. Our work supports future applications of non-invasive brain stimulation to restore impaired visually-guided behaviors by operating on top-down attentional modulatory mechanisms.

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