Responses of finger flexor and extensor muscles to transcranial magnetic stimulation during isometric force production tasks

Park, Woo Hyung; Li, Sheng

doi:10.1002/mus.23804

Cited by 8 publications

(8 citation statements)

References 26 publications

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“…However, if this were the case, a similar effect would be expected for our RT data, with shorter RT for muscles that have greater connectivity to reticulospinal pathways. Alternatively, in contrast to earlier reports of greater corticoneuronal contributions to extensors, recent neurophysiological reports have indicated greater functional corticospinal excitability for flexors compared to extensors (Godfrey et al, ; Koganemaru et al, ; McMillan et al, ; Park & Li, ; Vallence et al, ). The greater observed enhancement of response magnitude via the LAS for flexors may thereby be a product of response force being correlated with M1 activity (Ashe, ).…”

Section: Discussionmentioning

confidence: 83%

“…Such enhancement of response magnitude in an additive manner would suggest activation introduced via functional connections between the auditory cortex and primary motor cortex (M1; Marinovic, Tresilian, et al, ), or more directly from the brainstem to the spinal cord, converges with the activation associated with the prepared response. Furthermore, in flexors and extensors of the wrist ‐ muscles which differ in their corticospinal and reticulospinal connectivity (Cheney & Fetz, ; Clough, Kernell, & Phillips, ; de Noordhout et al, ; Fetz & Cheney, ; Godfrey, Lum, Chan, & Harris‐Love, ; Koganemaru et al, ; McMillan, Nougier, & Byblow, ; Palmer & Ashby, ; Park & Li, ; Vallence, Hammond, & Reilly, ), we investigated how muscle connectivity may impact the level or speed of LAS‐evoked neural activation by examining how our proposed multiplicative or additive effects, and/or the shortening of RT, may be modulated by efferent connectivity to the reticular formation. As the reticular formation has been proposed to mediate the shortening of RT via intense sensory stimulation, we predicted the enhancement of response magnitude and the shortening of RT would be greater in muscles that are more strongly connected to the reticular formation.…”

Section: Introductionmentioning

confidence: 99%

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Neural gain induced by startling acoustic stimuli is additive to preparatory activation

et al. 2019

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Loud acoustic stimuli presented during movement preparation can shorten reaction time and increase response forcefulness. We examined how efferent connectivity of an agonist muscle to reticulospinal and corticospinal pathways, and the level of prepared movement force, affect reaction time and movement execution when the motor response is triggered by an intense acoustic stimulus. In Experiment 1, participants executed ballistic wrist flexion and extension movements of low and high force in response to visual stimuli. A loud acoustic stimulus (LAS; 105 dBa) was presented simultaneously with the visual imperative stimulus in probe trials. In Experiment 2, participants executed ballistic wrist flexion movements ranging from 10%–50% of maximum voluntary contraction with a LAS presented in probe trials. The shortening of response initiation was not affected by movement type (flexion or extension) or prepared movement force. Enhancement of response magnitude, however, was proportionally greater for low force movements and for the flexor muscle. Changes in peak force induced by the intense acoustic stimulus indicated that the neural activity introduced to motor program circuits by acoustic stimulation is additive to the voluntary neural activity that occurs due to movement preparation, rather than multiplicative.

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Section: Discussionmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Neural gain induced by startling acoustic stimuli is additive to preparatory activation

et al. 2019

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“…Essentially, spastic flexors could be “therapeutically weakened” via botulinum toxin injection. As such, residual weak extensors may be able to function adequately, since the primary goal of the extensors is to open the hand or extend the elbow in preparation for functional operation by the flexors in most activities of daily living which does not require significant activation of the extensors ( Park and Li, 2013 ). We name it “therapeutic weakness” with the goal of improving motor control of the antagonist.…”

Section: Implications For Clinical Assessment and Managementmentioning

confidence: 99%

New insights into the pathophysiology of post-stroke spasticity

Francisco

2015

Front. Hum. Neurosci.

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184

191

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Spasticity is one of many consequences after stroke. It is characterized by a velocity-dependent increase in resistance during passive stretch, resulting from hyperexcitability of the stretch reflex. The underlying mechanism of the hyperexcitable stretch reflex, however, remains poorly understood. Accumulated experimental evidence has supported supraspinal origins of spasticity, likely from an imbalance between descending inhibitory and facilitatory regulation of spinal stretch reflexes secondary to cortical disinhibition after stroke. The excitability of reticulospinal (RST) and vestibulospinal tracts (VSTs) has been assessed in stroke survivors with spasticity using non-invasive indirect measures. There are strong experimental findings that support the RST hyperexcitability as a prominent underlying mechanism of post-stroke spasticity. This mechanism can at least partly account for clinical features associated with spasticity and provide insightful guidance for clinical assessment and management of spasticity. However, the possible role of VST hyperexcitability cannot be ruled out from indirect measures. In vivo measure of individual brainstem nuclei in stroke survivors with spasticity using advanced fMRI techniques in the future is probably able to provide direct evidence of pathogenesis of post-stroke spasticity.

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“…Both flexion and extension contractions were examined in order to assess whether the potential observable effects were muscle specific. Flexion and extension contractions were employed as these are an agonist/antagonist pair and have also been suggested to differ in the strength of their efferent contributions from the corticospinal and reticulospinal tracts (Cheney & Fetz, 1980; Clough et al, 1968; de Noordhout et al, 1999; Fetz & Cheney, 1980; Godfrey et al, 2013; Koganemaru et al, 2010; McInnes, Castellote, et al, 2020; McMillan et al, 2004; Palmer & Ashby, 1992; Park & Li, 2013; Quinn et al, 2018; Vallence et al, 2012). Contractions were maintained during preparation at 10% of the muscle’s MVC as this force level appeared to provide the most benefit in experiment one.…”

Section: Methods – Experiments Twomentioning

confidence: 99%

Engagement of the contralateral limb can enhance the facilitation of motor output by loud acoustic stimuli

McInnes

Nguyen²,

Carroll³

et al. 2021

Preprint

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When intense sound is presented during light muscle contraction, inhibition of the corticospinal tract is observed. During action preparation, this effect is reversed, with sound resulting in excitation of the corticospinal tract. We investigated how the combined maintenance of a muscle contraction during preparation for a ballistic action impacts the magnitude of the facilitation of motor output by a loud acoustic stimulus (LAS) – a phenomenon known as the StartReact effect. Participants executed ballistic wrist flexion movements and a LAS was presented simultaneously with the imperative signal in a subset of trials. We examined whether the force level or muscle used to maintain a contraction during preparation for the ballistic response impacted reaction time and/or the force of movements triggered by the LAS. These contractions were sustained either ipsilaterally or contralaterally to the ballistic response. The magnitude of facilitation by the LAS was greatest when low force flexion contractions were maintained in the limb contralateral to the ballistic response during preparation. There was little change in facilitation when contractions recruited the contralateral extensor muscle, or when they were sustained in the same limb that executed the ballistic response. We conclude that a larger network of neurons which may be engaged by a contralateral sustained contraction prior to initiation may be recruited by the LAS, further contributing to the motor output of the response. These findings may be particularly applicable in stroke rehabilitation where engagement of the contralesional side may increase the benefits of a LAS to the functional recovery of movement.

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Responses of finger flexor and extensor muscles to transcranial magnetic stimulation during isometric force production tasks

Abstract: These results suggest that FDS and EDC are controlled by different neural mechanisms, most likely attributable to their different functional roles in daily activities.

Cited by 8 publications

References 26 publications

Neural gain induced by startling acoustic stimuli is additive to preparatory activation

Neural gain induced by startling acoustic stimuli is additive to preparatory activation

New insights into the pathophysiology of post-stroke spasticity

Engagement of the contralateral limb can enhance the facilitation of motor output by loud acoustic stimuli

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