Transcranial Magnetic Stimulation: Principles and Applications

Koponen, Lari M.

doi:10.1007/978-3-030-43395-6_7

Cited by 17 publications

(14 citation statements)

References 63 publications

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“…Thus, larger driving currents (about 20 kA 60 ) are required to induce an electric field strong enough for stimulation, 6 generating excessive heat and large Lorentz forces that may damage conventional wires. 61 As far as we know, only very few examples of small coils for magnetic stimulations have been proposed in humans. For instance, Mori et al describe a small round coil to stimulate suprahyoid muscles obtaining hyoid elevation in patients affected by dysphagia but lacking technical details.…”

Section: Introductionmentioning

confidence: 99%

“…First is the reduced efficiency since the induced electric field rapidly falls off with distance. Thus, larger driving currents (about 20 kA 60 ) are required to induce an electric field strong enough for stimulation, 6 generating excessive heat and large Lorentz forces that may damage conventional wires 61 . As far as we know, only very few examples of small coils for magnetic stimulations have been proposed in humans.…”

Section: Introductionmentioning

confidence: 99%

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A study of flex miniaturized coils for focal nerve magnetic stimulation

et al. 2022

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Background: Peripheral magnetic stimulation (PMS) is emerging as a complement to standard electrical stimulation (ES) of the peripheral nervous system (PNS). PMS may stimulate sensory and motor nerve fibers without the discomfort associated with the ES used for standard nerve conduction studies. The PMS coils are the same ones used in transcranial magnetic stimulation (TMS) and lack focality and selectiveness in the stimulation. Purpose: This study presents a novel coil for PMS, developed using Flexible technologies, and characterized by reduced dimensions for a precise and controlled targeting of peripheral nerves. Methods: We performed hybrid electromagnetic (EM) and electrophysiological simulations to study the EM exposure induced by a novel miniaturized coil (or mcoil) in and around the radial nerve of the neuro-functionalized virtual human body model Yoon-Sun, and to estimate the current threshold to induce magnetic stimulation (MS) of the radial nerve. Eleven healthy subjects were studied with the mcoil, which consisted of two 15 mm diameter coils in a figure-ofeight configuration, each with a hundred turns of a 25 µm copper-clad four-layer foil. Sensory nerve action potentials (SNAPs) were measured in each subject using two electrodes and compared with those obtained from standard ES. The SNAPs conduction velocities were estimated as a performance metric. Results: The induced electric field was estimated numerically to peak at a maximum intensity of 39 V/m underneath the mcoil fed by 70 A currents. In such conditions, the electrophysiological simulations suggested that the mcoil elicits SNAPs originating at 7 mm from the center of the mcoil. Furthermore, the numerically estimated latencies and waveforms agreed with those obtained during the PMS experiments on healthy subjects, confirming the ability of the mcoil to stimulate the radial nerve sensory fibers. Conclusion: Hybrid EM-electrophysiological simulations assisted the development of a miniaturized coil with a small diameter and a high number of turns using flexible electronics. The numerical dosimetric analysis predicted the threshold current amplitudes required for a suprathreshold peripheral nerve sensory stimulation, which was experimentally confirmed. The developed and now validated computational pipeline will be used to improve the performances (e.g., focality and minimal currents) of new generations of mcoil designs.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A study of flex miniaturized coils for focal nerve magnetic stimulation

et al. 2022

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“…Transcranial magnetic stimulation (TMS) is a noninvasive technique to activate neurons in the brain [1,2].…”

Section: Significance and Challenges Of Thresholding In Tmsmentioning

confidence: 99%

“…Transcranial magnetic stimulation (TMS) is a noninvasive technique to activate neurons in the brain [1,2]. Certain pulse rhythms can further modulate neural circuits, i.e., change how they process endogenous signals [3].…”

Section: Introductionmentioning

confidence: 99%

Three Novel Methods for Determining Motor Threshold with Transcranial Magnetic Stimulation Outperform Conventional Procedures

Wang

Peterchev

Goetz

2022

Preprint

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BackgroundTranscranial magnetic stimulation (TMS) is a noninvasive neuromodulation method with both clinical and research applications. However, cortical neuronal variability presents challenges for TMS thresholding methods.ObjectiveTo analyze existing methods and their variations for obtaining TMS threshold, introduce new methods from other fields, and compare their performances in terms of speed and accuracy.MethodsWe examine existing methods based on the relative-frequency approximation of the probability definition of TMS threshold and adaptive methods based on a probabilistic threshold model and maximum-likelihood as well as maximum a posteriori estimation. Variations in the estimation and stepping procedure are included to improve the performance of the latter. We adapt a Bayesian estimation method which iteratively incorporates information from the TMS response into the probability density function and introduce a family of non-parametric stochastic root-finding method with different convergence criteria and stepping rules. In addition, we demonstrate accelerated threshold detection utilizing population-level prior information. We apply all thresholding methods on a virtual test bed and characterize their estimation error.ResultsThe relative-frequency methods require a large number of stimuli and, despite good accuracy on the population level, have wide error distributions for individual subjects. The parametric estimation methods obtain threshold much faster, and their accuracy depends on their estimation and stepping rules, with their performance significantly improved when population-level prior information is included. Stochastic root-finding methods are comparable to adaptive estimation methods but are much simpler to implement and do not rely on an underlying model.ConclusionTMS thresholding methods have a wide range of behavior and difference in performance and the optimal methods requires various considerations of trade-off.

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“…One technique which has gained increasing interest is Transcranial Focused Ultrasound (tFUS), the use of a low-intensity acoustic wave to stimulate the brain with acoustic energy with high precision targeting capabilities (Blackmore et al, 2019; Kamimura et al, 2020; Naor et al, 2016; Tufail et al, 2010, 2011; Tyler et al, 2008). Although many other neuromodulatory techniques exist, including deep brain stimulation (DBS) (Ashkan et al, 2017; Gardner, 2013; Lozano et al, 2019), transcranial magnetic stimulation (TMS) (Chail et al, 2018; Koponen & Peterchev, 2020), transcranial direct current stimulation (tDCS) (Bikson & Rahman, 2013; Giordano et al, 2017; Nitsche & Paulus, 2000), and optogenetics (Boyden et al, 2005; Mahmoudi et al, 2017), tFUS has the potential to offer high spatial focality and deep brain penetration as a noninvasive neuromodulation technique applicable to human subjects. Chemical methods and optogenetics can allow for high temporal resolution and/or cell type specificity, but are invasive approaches that require introducing foreign substances to the brain (Chen et al, 2018; Mahmoudi et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Ultrasound Neuromodulation and Correlation Change in the Rat Somatosensory Cortex

Ramachandran

Niu

et al. 2022

Preprint

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Transcranial focused ultrasound (tFUS) is a neuromodulation technique which has been the focus of increasing interest for noninvasive brain stimulation with high spatial specificity. Its ability to excite and inhibit neural circuits as well as to modulate perception and behavior has been demonstrated, however, we currently lack understanding of how tFUS modulates the ways neurons interact with each other. This understanding would help explain tFUS's mechanism of high-level neuromodulation and allow future development of therapies for neurological disorders. In this study we investigate how tFUS modulates neural interaction and response to peripheral electrical limb stimulation through intracranial multi-electrode recordings in the rat somatosensory cortex. We deliver ultrasound in a pulsed pattern to attempt to induce frequency dependent plasticity in a manner similar to that found following electrical stimulation. We show that neural firing in response to peripheral electrical stimulation is increased after ultrasound stimulation at all frequencies, showing tFUS induced excitation in individual neurons in vivo. We demonstrate tFUS frequency dependent pairwise correlation changes between neurons, with both potentiation and depression observed at different frequencies. These results extend previous research showing tFUS to be capable of inducing synaptic depression and demonstrate its ability to modulate network dynamics as a whole.

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Transcranial Magnetic Stimulation: Principles and Applications

Cited by 17 publications

References 63 publications

A study of flex miniaturized coils for focal nerve magnetic stimulation

A study of flex miniaturized coils for focal nerve magnetic stimulation

Three Novel Methods for Determining Motor Threshold with Transcranial Magnetic Stimulation Outperform Conventional Procedures

Ultrasound Neuromodulation and Correlation Change in the Rat Somatosensory Cortex

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