Agonist contraction during intermittent theta burst stimulation enhances motor cortical plasticity of the wrist flexors

Mirdamadi, Jasmine L.; Suzuki, L.Y.; Meehan, Sean K.

doi:10.1016/j.neulet.2015.02.020

Cited by 7 publications

(12 citation statements)

References 26 publications

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“…The ECR motor cortical hotspot was 44.7± 5.7 mm lateral and 13.5±7.0 mm anterior to the vertex. Consistent with our previous work (Mirdamadi et al, 2015) and others (Suzuki et al, 2012) FCR resting motor threshold was significantly greater than ECR resting motor threshold regardless of session [Main Effect Muscle : F 1,14 =32.05, p <0.0001, FCR=42±8 (mean±standard deviation), ECR=39±8]. Resting motor thresholds for each muscle were not different across session [Interaction Session×Muscle : F 1,14 =0.10, p =0.76; Main Effect Session : F 1,14 =1.00, p =0.33].…”

Section: Resultssupporting

confidence: 94%

“…An interesting result from the current study in light of our previous work is that both the facilitatory effect of iTBS (Mirdamadi et al, 2015) and the suppressive effect of cTBS upon the FCR are stronger in individuals with lower FCR-ECR threshold differences. The similar direction of the relationship is consistent with a common underlying mechanism mediating TBS-induced plasticity.…”

Section: Discussionsupporting

confidence: 67%

“…Consistent with a common underlying mechanism mediating both forms of TBS-induced plasticity (Huang et al, 2011; Hamada et al, 2013) and our previous work using iTBS (Mirdamadi et al, 2015) we hypothesized that individuals with FCR thresholds that were lower or in close proximity to their ECR threshold would demonstrate stronger suppression of FCR MEPs post-cTBS. Similarly, we hypothesized that individuals with FCR thresholds that were increasingly greater than their ECR threshold would demonstrate progressively stronger suppression of ECR MEPs.…”

Section: Introductionsupporting

confidence: 64%

“…Any trials in which root mean square error of either the targeted or non-targeted muscle exceeded 15 μV were excluded from subsequent analysis (Ackerley et al, 2011; Mirdamadi et al, 2015). The mean peak-to-peak amplitude of the MEP was then derived for each combination of Time (pre, T10, T20, T30), Muscle (Targeted, Non-targeted), Hotspot (FCR, ECR) and Session (cTBS-Relax, cTBS-Contract, cTBS-Alone).…”

Section: Methodsmentioning

confidence: 99%

“…However, relatively little research has studied variability of transcranial magnetic stimulation induced aftereffects in the extrinsic muscles of the hand, such as the wrist flexors and extensors. Relative differences in corticospinal control (Fetz and Cheney, 1980; Palmer and Ashby, 1992; Park et al, 2004) and/or stimulation specific transcranial magnetic parameters (Mirdamadi et al, 2015) may determine which intracortical networks are most readily recruited from overlapping cortical representations at the site of stimulation.…”

Section: Introductionmentioning

confidence: 99%

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Motor cortical plasticity in extrinsic hand muscles is determined by the resting thresholds of overlapping representations

2016

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Knowledge of the properties that govern the effectiveness of transcranial magnetic stimulation (TMS) interventions is critical to clinical application. Extrapolation to clinical populations has been limited by high inter-subject variability and a focus on intrinsic muscles of the hand in healthy populations. Therefore, the current study assessed variability of continuous theta burst stimulation (cTBS), a patterned TMS protocol, across an agonist–antagonist pair of extrinsic muscles of the hand. Secondarily, we assessed whether concurrent agonist contraction could enhance the efficacy of cTBS. Motor evoked potentials (MEP) were simultaneously recorded from the agonist flexor (FCR) and antagonist extensor (ECR) carpi radialis before and after cTBS over the FCR hotspot. cTBS was delivered with the FCR relaxed (cTBS-Relax) or during isometric wrist flexion (cTBS-Contract). cTBS-Relax suppressed FCR MEPs evoked from the FCR hotspot. However, the extent of FCR MEP suppression was strongly correlated with the relative difference between FCR and ECR resting motor thresholds. cTBS-Contract decreased FCR suppression but increased suppression of ECR MEPs elicited from the FCR hotspot. The magnitude of ECR MEP suppression following cTBS-Contract was independent of the threshold-amplitude relationships observed with cTBS-Relax. Contraction alone had no effect confirming the effect of cTBS-Contract was driven by the interaction between neuromuscular activity and cTBS. Interactions across muscle representations should be taken into account when predicting cTBS outcomes in healthy and clinical populations. Contraction during cTBS may be a useful means of focusing aftereffects when differences in baseline excitability across overlapping agonist–antagonist cortical representations may mitigate the inhibitory effect of cTBS.

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Section: Resultssupporting

confidence: 94%

Section: Discussionsupporting

confidence: 67%

Section: Introductionsupporting

confidence: 64%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Motor cortical plasticity in extrinsic hand muscles is determined by the resting thresholds of overlapping representations

2016

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Differential plasticity of extensor and flexor motor cortex representations following visuomotor adaptation

et al. 2018

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Representations within the primary motor cortex (M1) are capable of rapid functional changes following motor learning, known as use-dependent plasticity. GABAergic inhibition plays a role in use-dependent plasticity. Evidence suggests a different capacity for plasticity of distal and proximal upper limb muscle representations. However, it is unclear whether the motor cortical representations of forearm flexor and extensor muscles also have different capacities for plasticity. The current study used transcranial magnetic stimulation to investigate motor cortex excitability and inhibition of forearm flexor and extensor representations before and after performance of a visuomotor adaptation task that primarily targeted flexors and extensors separately. There was a decrease in extensor and flexor motor-evoked potential (MEP) amplitude after performing the extensor adaptation, but no change in flexor and extensor MEP amplitude after performing the flexor adaptation. There was also a decrease in motor cortical inhibition in the extensor following extensor adaptation, but no change in motor cortical inhibition in the flexor muscle following flexor adaptation or either of the non-prime mover muscles. Findings suggest that the forearm extensor motor cortical representation exhibits plastic change following adaptive motor learning, and broadly support the distinct neural control of forearm flexor and extensor muscles.

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Aftereffects of Intermittent Theta-Burst Stimulation in Adjacent, Non-Target Muscles

et al. 2019

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Agonist contraction during intermittent theta burst stimulation enhances motor cortical plasticity of the wrist flexors

Cited by 7 publications

References 26 publications

Motor cortical plasticity in extrinsic hand muscles is determined by the resting thresholds of overlapping representations

Motor cortical plasticity in extrinsic hand muscles is determined by the resting thresholds of overlapping representations

Differential plasticity of extensor and flexor motor cortex representations following visuomotor adaptation

Aftereffects of Intermittent Theta-Burst Stimulation in Adjacent, Non-Target Muscles

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