Single-Pulse Transcranial Magnetic Stimulation (TMS) Protocols and Outcome Measures

Farzan, Faranak

doi:10.1007/978-1-4939-0879-0_5

Cited by 19 publications

(25 citation statements)

References 179 publications

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“…According to this model, beta events arise from simultaneous weak proximal and strong distal excitatory drives to pyramidal neurons in layers II/III and V. This same excitatory projection likely also synapses on inhibitory neurons in superficial cortical layers (6,31,8), which is consistent with the notion that sensorimotor beta activity produces an inhibitory cortical state (32,33). Low-intensity TMS is known to preferentially activate layer V corticospinal neurons trans-synaptically through layer II/III excitatory and inhibitory interneurons, as well as cortico-cortical connections (34,35). Thus, even when beta events do not predict an experimental outcome more strongly than mean beta power (8,9, and the current work), accounting for event characteristics can offer a more physiologically-informed framework for interpreting empirical findings.…”

Section: Discussionsupporting

confidence: 73%

Beta rhythm events predict corticospinal motor output

Hussain

Cohen

Bönstrup

2019

Preprint

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The beta rhythm (15-30 Hz) is a prominent signal of sensorimotor cortical activity. This rhythm is not sustained but occurs non-rhythmically as brief events of a few (1-2) oscillatory cycles.Recent work on the relationship between these events and sensorimotor performance suggests that they are the biologically relevant elements of the beta rhythm. However, the influence of these events on corticospinal excitability, a mechanism through which the primary motor cortex controls motor output, is unknown. Here, we addressed this question by evaluating relationships between beta event characteristics and corticospinal excitability in healthy adults. Results show that the number, amplitude, and timing of beta events preceding transcranial magnetic stimulation (TMS) each significantly predict MEP amplitudes. However, beta event characteristics did not explain additional MEP amplitude variance beyond that explained by mean beta power alone, suggesting that conventional beta power measures and beta event characteristics similarly capture natural variation in human corticospinal excitability. Despite this lack of additional explained variance, these results provide first evidence that endogenous beta oscillatory events shape human corticospinal excitability.

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Section: Discussionsupporting

confidence: 73%

Beta rhythm events predict corticospinal motor output

Hussain

Cohen

Bönstrup

2019

Preprint

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“…According to this model, beta events arise from simultaneous weak proximal and strong distal excitatory drives to pyramidal neurons in layers II/III and V. This same excitatory projection likely also synapses on inhibitory neurons in superficial cortical layers 6,8,15 , which is consistent with the notion that sensorimotor beta activity produces an inhibitory cortical state 31,32 . TMS at lower intensities is known to preferentially activate layer V corticospinal neurons trans-synaptically through layer II/III excitatory and inhibitory interneurons, as well as cortico-cortical connections 33,34 . This indirect activation of layer V corticospinal neurons produces I-waves at the spinal level and MEPs at the muscle level.…”

Section: Discussionmentioning

confidence: 99%

“…During beta events, the excitatory drive to inhibitory interneurons in superficial cortical layers may thus increase the inhibitory tone of this interneuron pool, generating an inverse relationship between beta event presence and the elicited MEP size as previously reported 24,25 . TMS at higher intensities 35 , in contrast, also directly activates the axons of layer V corticospinal neurons 33,34 , which could feasibly overcome any inhibitory tone produced by inhibitory interneurons in superficial cortical layers. The strong excitatory drive to layer V corticospinal neurons that generates beta events may amplify this direct axonal activation by increasing the pool of layer V corticospinal neurons that are recruited by TMS, producing a positive relationship between beta event presence and MEP size as observed here.…”

Section: Discussionmentioning

confidence: 99%

Beta rhythm events predict corticospinal motor output

Hussain

Cohen

Bönstrup

2019

Sci Rep

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The beta rhythm (15–30 Hz) is a prominent signal of sensorimotor cortical activity. This rhythm is not sustained but occurs non-rhythmically as brief events of a few (1–2) oscillatory cycles. Recent work on the relationship between these events and sensorimotor performance suggests that they are the biologically relevant elements of the beta rhythm. However, the influence of these events on corticospinal excitability, a mechanism through which the primary motor cortex controls motor output, is unknown. Here, we addressed this question by evaluating relationships between beta event characteristics and corticospinal excitability in healthy adults. Results show that the number, amplitude, and timing of beta events preceding transcranial magnetic stimulation (TMS) each significantly predicted motor-evoked potential (MEP) amplitudes. However, beta event characteristics did not explain additional MEP amplitude variance beyond that explained by mean beta power alone, suggesting that conventional beta power measures and beta event characteristics similarly captured natural variation in human corticospinal excitability. Despite this lack of additional explained variance, these results provide first evidence that endogenous beta oscillatory events shape human corticospinal excitability.

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“…Since MEPs were recorded during active contractions (i.e., 10% MVC), it was also possible to record the cortical silent period (CSP) of the MEPs from the same trials. CSP was calculated from the responses evoked at 70% of the stimulator output (Farzan 2014).…”

Section: Transcranial Magnetic Stimulation (Tms)mentioning

confidence: 99%

“…The average MEP amplitudes were plotted relative to the TMS stimulation intensities and a linear fit was obtained using simple linear regression. The slope of the linear regression line was used to define the gain parameter of the input-output relationship curve (Figure 2A and Figure 2E) (Farzan 2014).…”

Section: Mepsmentioning

confidence: 99%

Cortical re-organization after traumatic brain injury elicited using functional electrical stimulation therapy: A case report

Milosevic

Nakanishi²,

Sasaki³

et al. 2020

Preprint

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Functional electrical stimulation therapy (FEST) can improve motor function after neurological injuries. However, little is known about cortical re-organization after FEST and weather it can improve upper-limb motor function after traumatic brain injury (TBI). Therefore, our study examined cortical and motor changes in a single male participant with chronic TBI suffering from mild motor impairment during 3-months of FEST and at 3-months follow-up. FEST was applied to enable upper-limb grasping and reaching movements during each session, which was performed for 45-60 min, 3 days per week, over 12-weeks. Short-term assessments were examined before and after each session, while long-term assessments were performed at baseline, after 6- and 12-weeks of FEST, and during follow-up 6- and 12-weeks after completing FEST. Short-term assessments carried out using transcranial magnetic stimulation (TMS) showed reduced cortical silent period (CSP), which is related to cortical and/or subcortical inhibition. At the same time, no changes in motor evoked potentials (MEP) were observed, suggesting corticospinal excitability was unaffected. Long-term assessments indicate increased MEP corticospinal excitability after 12-weeks of FEST, which remained during both follow-ups, while no changes in CSP were observed. Similarly, long-term assessments using TMS mapping showed larger hand MEP area in the primary motor cortex (M1) after 12-weeks of FEST as well as during both follow-ups. Corroborating TMS results, fMRI imaging data showed M1, as well as sensory, premotor, parietal area, and supplementary motor area activations increased after 12-weeks of FEST and during both follow-ups. While clinical scores did not change considerably, writing test performance indicates mild improvements after FEST. Our results suggest that FEST can effectively increase cortical activations, while writing tests confirmed functional improvements in fine motor function even after chronic TBI. These results demonstrated long-term recovery mechanisms of FEST, which include cortical re-organization or neuroplasticity to improve motors function after neurological injury.

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Single-Pulse Transcranial Magnetic Stimulation (TMS) Protocols and Outcome Measures

Cited by 19 publications

References 179 publications

Beta rhythm events predict corticospinal motor output

Beta rhythm events predict corticospinal motor output

Beta rhythm events predict corticospinal motor output

Cortical re-organization after traumatic brain injury elicited using functional electrical stimulation therapy: A case report

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