scholarly journals A Neurostimulator System for Real, Sham, and Multi-Target Transcranial Magnetic Stimulation

2021 ◽  
Author(s):  
Majid Memarian Sorkhabi ◽  
Timothy Denison
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Pulse Width Modulation ◽  
Pulse Generator ◽  
Control Method ◽  
Physical Distance ◽  
Magnetic Pulse ◽  
Electronic Control ◽  
Channel Modulation ◽  
Measured System

Background: Transcranial magnetic stimulation (TMS) is a clinically effective therapeutic instrument used to modulate neural activity. Despite three decades of research, two challenging issues remain, the possibility of changing the 1) stimulated spot and 2) stimulation type (real or sham) without physically moving the coil. Objective: In this study, a second-generation programmable TMS (pTMS2) device with advanced stimulus shaping is introduced that uses a 5-level cascaded H-bridge inverter and phase-shifted pulse-width modulation (PWM). The principal idea of this research is to obtain real, sham, and multi-locus stimulation with the same TMS system. Methods: We propose a two-channel modulation-based magnetic pulse generator and a novel coil arrangement, consisting of two circular coils with a physical distance of 20 mm between the coils and a control method for modifying the effective stimulus intensity, which leads to the live steerability of the location and type of stimulation. Results: Based on the measured system performance, the stimulation profile can be steered 20 mm along a line from the centroid of the coil locations by modifying the modulation index. Conclusion: The proposed system supports electronic control of the stimulation spot without physical coil movement, resulting in tunable modulation of targets, which is a crucial step towards automated TMS machines.

A Network Model of Perceptual Suppression Induced by Transcranial Magnetic Stimulation

2004 ◽  
Vol 16 (2) ◽  
pp. 309-331 ◽  
Author(s):  
Yoichi Miyawaki ◽  
Masato Okada
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Network Model ◽  
Magnetic Stimulation ◽  
Experimental Studies ◽  
Afferent Input ◽  
Network Activity ◽  
Neural Population ◽  
High Temporal Resolution ◽  
Magnetic Pulse ◽  
Dynamical Interaction

We modeled the inhibitory effects of transcranial magnetic stimulation (TMS) on a neural population. TMS is a noninvasive technique, with high temporal resolution, that can stimulate the brain via a brief magnetic pulse from a coil placed on the scalp. Because of these advantages, TMS is extensively used as a powerful tool in experimental studies of motor, perception, and other functions in humans. However, the mechanisms by which TMS interferes with neural activities, especially in terms of theoretical aspects, are totally unknown. In this study, we focused on the temporal properties of TMS-induced perceptual suppression, and we computationally analyzed the response of a simple network model of a sensory feature detector system to a TMS-like perturbation. The perturbation caused the mean activity to transiently increase and then decrease for a long period, accompanied by a loss in the degree of activity localization. When the afferent input consisted of a dual phase, with a strong transient component and a weak sustained component, there was a critical latency period of the perturbation during which the network activity was completely suppressed and converged to the resting state. The range of the suppressive period increased with decreasing afferent input intensity and reached more than 10 times the time constant of the neuron. These results agree well with typical experimental data for occipital TMS and support the conclusion that dynamical interaction in a neural population plays an important role in TMS-induced perceptual suppression.

scholarly journals Effect of stimulus orientation and intensity on short-interval intracortical inhibition (SICI) and facilitation (SICF): A multi-channel transcranial magnetic stimulation study

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0257554
Author(s):  
Sergei Tugin ◽  
Victor H. Souza ◽  
Maria A. Nazarova ◽  
Pavel A. Novikov ◽  
Aino E. Tervo ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Short Interval ◽  
Intracortical Inhibition ◽  
Stimulus Orientation ◽  
Electronic Control ◽  
Field Orientation ◽  
Neuronal Populations ◽  
Resting Motor Threshold ◽  
Strongly Connected

Besides stimulus intensities and interstimulus intervals (ISI), the electric field (E-field) orientation is known to affect both short-interval intracortical inhibition (SICI) and facilitation (SICF) in paired-pulse transcranial magnetic stimulation (TMS). However, it has yet to be established how distinct orientations of the conditioning (CS) and test stimuli (TS) affect the SICI and SICF generation. With the use of a multi-channel TMS transducer that provides electronic control of the stimulus orientation and intensity, we aimed to investigate how changes in the CS and TS orientation affect the strength of SICI and SICF. We hypothesized that the CS orientation would play a major role for SICF than for SICI, whereas the CS intensity would be more critical for SICI than for SICF. In eight healthy subjects, we tested two ISIs (1.5 and 2.7 ms), two CS and TS orientations (anteromedial (AM) and posteromedial (PM)), and four CS intensities (50, 70, 90, and 110% of the resting motor threshold (RMT)). The TS intensity was fixed at 110% RMT. The intensities were adjusted to the corresponding RMT in the AM and PM orientations. SICI and SICF were observed in all tested CS and TS orientations. SICI depended on the CS intensity in a U-shaped manner in any combination of the CS and TS orientations. With 70% and 90% RMT CS intensities, stronger PM-oriented CS induced stronger inhibition than weaker AM-oriented CS. Similar SICF was observed for any CS orientation. Neither SICI nor SICF depended on the TS orientation. We demonstrated that SICI and SICF could be elicited by the CS perpendicular to the TS, which indicates that these stimuli affected either overlapping or strongly connected neuronal populations. We concluded that SICI is primarily sensitive to the CS intensity and that CS intensity adjustment resulted in similar SICF for different CS orientations.

scholarly journals Fine multi-coil electronic control of transcranial magnetic stimulation: effects of stimulus orientation and intensity

2021 ◽  
Author(s):  
Victor H. Souza ◽  
Jaakko O. Nieminen ◽  
Sergei Tugin ◽  
Lari M. Koponen ◽  
Oswaldo Baffa ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Neurological Diseases ◽  
Brain Activity ◽  
Logistic Function ◽  
Stimulus Orientation ◽  
High Angular Resolution ◽  
Electronic Control ◽  
Fast Control ◽  
Electric Filed

Despite the evident benefit of transcranial magnetic stimulation (TMS) to probe human brain function and treat neurological diseases, current technology allows only a slow, mechanical adjustment of the electric filed orientation. Automated and fast control of the TMS orientation is critical to enable synchronizing the stimulation with the ongoing brain activity. We overcome these limitations with a two-coil electronically controlled TMS transducer to define precisely the pulse orientation (~1-degree steps) without mechanical movement. We validated the technology by determining the dependency of motor evoked responses on the stimulus orientation and intensity with high angular resolution. The motor response was found to follow a logistic function of the stimulus orientation, which helps to disentangle the TMS neuronal effects. The electronic control of the TMS electric field is a decisive step towards automated brain stimulation protocols with enhanced accuracy of stimulus targeting and timing for better diagnostics and improved clinical efficacy.

Trajectory tracking control of robotic transcranial magnetic stimulation

2019 ◽  
Vol 12 (2) ◽  
pp. 245-259 ◽  
Author(s):  
Zecai Lin ◽  
Xin Wang ◽  
Jian Yang
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Augmented Reality ◽  
Trajectory Tracking ◽  
Force Control ◽  
Tracking Control ◽  
Magnetic Stimulation ◽  
Control Method ◽  
Trajectory Tracking Control ◽  
Content Type ◽  
Augmented Reality Technology

Purpose Transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation technique. Based on the unique functions of TMS, it has been widely used in clinical, scientific research and other fields. Nowadays, the robot-assisted automatic TMS has become the trend. In order to simplify the operation procedures of robotic TMS and reduce the costs, the purpose of this paper is to apply the marker-based augmented-reality technology to robotic TMS system. Design/methodology/approach By using the marker of ARToolKitPlus library and monocular camera, the patient’s head is positioned in real time. Furthermore, the force control is applied to keep contact between the coil and subject’s head. Findings The authors fuse with visual positioning which is based on augmented-reality and force-control technologies to track the movements of the patient’s head, bring the coil closer to the stimulation site and increase treatment effects. Experimental results indicate that the trajectory tracking control of robotic TMS system designed in this paper is practical and flexible. Originality/value This paper provides a trajectory tracking control method for the robotic TMS. The marker-based augmented-reality technology is implemented which simplifies the operation procedures of robotic TMS as well as reduce the costs. During the treatment process, the patients would wear an AR glasses, which can help patients relax through virtual scenes and reduce the uncomfortableness produce by treatment.

scholarly journals TMS SMART – Scalp Mapping of Annoyance Ratings and Twitches caused by Transcranial Magnetic Stimulation

2017 ◽  
Author(s):  
Lotte Meteyard ◽  
Nicholas Holmes
Keyword(s):  
Reaction Time ◽  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Reaction Time Task ◽  
Single Pulse ◽  
Muscle Fibres ◽  
Magnetic Pulse ◽  
Subjective Ratings ◽  
Time Task ◽  
Scalp Location

AbstractThe magnetic pulse generated during Transcranial magnetic stimulation [TMS] also stimulates cutaneous nerves and muscle fibres, with the most commonly reported side effect being muscle twitches and sometimes painful sensations. These sensations affect behaviour during experimental tasks, presenting a potential confound for ‘online’ single-pulse TMS studies. Our objective was to systematically map the degree of disturbance (ratings of annoyance, pain, and muscle twitches) caused by TMS at 43 locations across the scalp. Ten participants provided ratings whilst completing a choice reaction time task, and ten participants provided ratings whilst completing a ‘flanker’ reaction time task. TMS over frontal and inferior regions resulted in the highest ratings of annoyance, pain, and muscle twitches caused by TMS. In separate analyses we predicted the difference in reaction times (RT) under TMS by scalp location and subjective ratings. Frontal and inferior scalp locations showed the greatest cost to RTs under TMS (i.e., slowing), with midline sites showing no or minimal slowing. Increases in subjective ratings of disturbance predicted longer RTs under TMS. Critically, ratings were a better predictor of the cost of TMS than scalp location or scalp-to-cortex distance, and the more difficult ‘flanker’ task showed a greater effect of subjective disturbance. The peripheral sensations and discomfort caused by TMS pulses significantly and systematically influence RTs during single-pulse, online TMS experiments. We provide the data as an online resource (http://www.tms-smart.info) so that researchers can select control sites that account for the level of general interference in task performance caused by online single-pulse TMS.

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