A Model of TMS-induced I-waves in Motor Cortex

Rusu, Cătălin V.; Murakami, Max; Ziemann, Ulf; Triesch, Jochen

doi:10.1016/j.brs.2014.02.009

Cited by 117 publications

(78 citation statements)

References 70 publications

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“…Thus, the morphology of L3 PNs might result in their higher excitability in response to TMS. In addition, the lower stimulation thresholds of the L3 PNs are consistent with lower stimulation intensities required to produce I-waves 50, 62 , and the higher stimulation intensities required to produce D-waves.…”

Section: Discussionsupporting

confidence: 59%

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A multi-scale computational model of the effects of TMS on motor cortex

et al. 2017

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The detailed biophysical mechanisms through which transcranial magnetic stimulation (TMS) activates cortical circuits are still not fully understood. Here we present a multi-scale computational model to describe and explain the activation of different pyramidal cell types in motor cortex due to TMS. Our model determines precise electric fields based on an individual head model derived from magnetic resonance imaging and calculates how these electric fields activate morphologically detailed models of different neuron types. We predict neural activation patterns for different coil orientations consistent with experimental findings. Beyond this, our model allows us to calculate activation thresholds for individual neurons and precise initiation sites of individual action potentials on the neurons' complex morphologies. Specifically, our model predicts that cortical layer 3 pyramidal neurons are generally easier to stimulate than layer 5 pyramidal neurons, thereby explaining the lower stimulation thresholds observed for I-waves compared to D-waves. It also shows differences in the regions of activated cortical layer 5 and layer 3 pyramidal cells depending on coil orientation. Finally, it predicts that under standard stimulation conditions, action potentials are mostly generated at the axon initial segment of cortical pyramidal cells, with a much less important activation site being the part of a layer 5 pyramidal cell axon where it crosses the boundary between grey matter and white matter. In conclusion, our computational model offers a detailed account of the mechanisms through which TMS activates different cortical pyramidal cell types, paving the way for more targeted application of TMS based on individual brain morphology in clinical and basic research settings. Keywords

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Section: Discussionsupporting

confidence: 59%

“…We calculated a monophasic pulse that induced a fluctuating magnetic field through an RLC circuit as detailed in 50,…”

Section: Methodsmentioning

confidence: 99%

A multi-scale computational model of the effects of TMS on motor cortex

et al. 2017

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“…It is still not fully understood what modulates ICF (Ni et al 2007), although at baseline and during non-fatiguing voluntary activity, activation of cortico-cortical pyramidal cells and their axons are thought to be involved (Chen et al 1998). In contrast, a recent model proposes that transmitter release from inhibitory interneurons may be depressed following their activation by the subthreshold conditioning TMS, thus, decreasing the inhibitory component to a test stimulus evoked at ISIs greater than 5 ms (Rusu et al 2014). This model implies that a decrease in SICI would lead to a decrease in ICF as occurred in the current study, although the different time course of recovery of SICI and ICF is not consistent with such a direct link.…”

Section: Discussionmentioning

confidence: 99%

Short-interval cortical inhibition and intracortical facilitation during submaximal voluntary contractions changes with fatigue

et al. 2016

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This study determined whether short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) change during a sustained submaximal isometric contraction. On two days, 12 participants (6 men, 6 women) performed brief (7-s) elbow flexor contractions before and after a 10-minute fatiguing contraction; all contractions were performed at the level of integrated electromyographic activity (EMG) which produced 25% maximal unfatigued torque. During the brief 7-s and 10-minute submaximal contractions, single (test) and paired (conditioning-test) transcranial magnetic stimuli were applied over the motor cortex (5s apart) to elicit motor evoked potentials (MEPs) in biceps brachii. SICI and ICF were elicited on separate days, with a conditioning-test interstimulus interval of 2.5ms and 15ms respectively. On both days, integrated EMG remained constant while torque fell during the sustained contraction by ~51.5% from control contractions, perceived effort increased 3 fold and MVC declined by 21–22%. For SICI, the conditioned MEP during control contractions (74.1±2.5% of unconditioned MEP) increased (less inhibition) during the sustained contraction (last 2.5 min: 86.0±5.1%; P<0.05). It remained elevated in recovery contractions at 2 minutes (82.0±3.8%; P<0.05) and returned toward control at 7-mins recovery (76.3±3.2%). ICF during control contractions (conditioned MEP 129.7±4.8% of unconditioned MEP) decreased (less facilitation) during the sustained contraction (last 2.5 min: 107.6±6.8% P<0.05) and recovered to 122.8±4.3% during contractions after 2 minutes of recovery. Both intracortical inhibitory and facilitatory circuits become less excitable with fatigue when assessed during voluntary activity, but their different time courses of recovery suggest different mechanisms for the fatigue-related changes of SICI and ICF.

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“…With both transcranial electrical stimulation and TMS, high-frequency synchronized descending volleys of activity are recorded in the epidural space [30–32]. However, there is still some debate on the synaptic mechanisms at the origin of I waves [33]. …”

Section: Discussionmentioning

confidence: 99%

The in vivo reduction of afferent facilitation induced by low frequency electrical stimulation of the motor cortex is antagonized by cathodal direct current stimulation of the cerebellum

Taib

Manto

2016

cerebellum ataxias

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BackgroundLow-frequency electrical stimulation to the motor cortex (LFSMC) depresses the excitability of motor circuits by long-term depression (LTD)-like effects. The interactions between LFSMC and cathodal direct current stimulation (cDCS) over the cerebellum are unknown.MethodsWe assessed the corticomotor responses and the afferent facilitation of corticomotor responses during a conditioning paradigm in anaesthetized rats. We applied LFSMC at a frequency of 1 Hz and a combination of LFSMC with cDCS.ResultsLFSMC significantly depressed both the corticomotor responses and the afferent facilitation of corticomotor responses. Simultaneous application of cDCS over the cerebellum antagonized the depression of corticomotor responses and cancelled the depression of the afferent facilitation.ConclusionOur results demonstrate that cDCS of the cerebellum is a potent modulator the inhibition of the motor circuits induced by LFSMC applied in vivo. These results expand our understanding of the effects of cerebellar DCS on motor commands and open novel applications for a cerebellar remote control of LFSMC-induced neuroplasticity. We suggest that the cerebellum acts as a neuronal machine supervising not only long-term potentiation (LTP)-like effects, but also LTD-like effects in the motor cortex, two mechanisms which underlie cerebello-cerebral interactions and the cerebellar control of remote plasticity. Implications for clinical ataxiology are discussed.

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A Model of TMS-induced I-waves in Motor Cortex

Cited by 117 publications

References 70 publications

A multi-scale computational model of the effects of TMS on motor cortex

A multi-scale computational model of the effects of TMS on motor cortex

Short-interval cortical inhibition and intracortical facilitation during submaximal voluntary contractions changes with fatigue

The in vivo reduction of afferent facilitation induced by low frequency electrical stimulation of the motor cortex is antagonized by cathodal direct current stimulation of the cerebellum

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