This work was supported by the University of Michigan: MCubed Scholars Program and School of Kinesiology.

The authors have nothing to disclose.

The dual-site TMS method described here can be employed to investigate functional interactions between different cortical areas interconnected with the primary motor cortex while a participant is at rest or planning a goal-directed action. While brain imaging is correlative, basic knowledge from dual-site TMS methods can reveal causal brain-behavior relations associated with changes in cortico-cortical circuits. In addition, cortical paired associative stimulation with two TMS coils applied in areas interconnected with M...

Noninvasive brain stimulation is a promising assessment tool and treatment for many neurological disorders, such as Parkinson&#39;s disease, Alzheimer&#39;s disease, and stroke1,2,3,4. There is accumulating evidence establishing the relationship between the behavioral manifestations of neurological diseases and abnormalities of cortical excitability, neuroplasticity, cortico-cortical and cortico-subcortical connectivity5,6. Therefore, basic knowledge about brain network dynamics and plasticity in neurological conditions can provide invaluable insight into disease diagnosis, progression, and response to therapy. Functional magnetic resonance imaging (fMRI) is a useful tool to understand the complex relations between brain and behavior in both healthy and diseased brain networks and has the potential to improve treatment based on a network perspective7,8,9. However, fMRI is correlational in nature and cannot provide a causal link between brain function and behavior, nor manipulate functional connectivity to restore abnormal neural circuits associated with behavioral impairments in patients10,11,12. Transcranial magnetic stimulation (TMS) can both causally measure and modulate human brain function and behavior in health and disease3,13,14,15.
TMS is a safe, noninvasive method to stimulate the human brain16,17 and can be used to induce and measure plasticity18. This method can advance our understanding of causal relationships between individual brain areas and behavior10,11,12,19 and their specific functional interactions with other nodes of a brain network20,21,22,23. To date, most studies have focused on the human motor system, given that TMS to the hand area of the motor cortex (M1) can produce motor evoked potentials (MEPs) as physiological readouts for changes associated with motor behavior24, allowing examination of different inhibitory and excitatory circuits at the system level in the human brain25. Recent advances using a conditioning test TMS approach with two coils show that it is possible to measure functional interactions between different cortical areas. In the motor system, dual-site TMS experiments show that inputs from cortical areas interconnected with M1 can change with task demands, age, or disease14,26. Seminal work by Ferbert and colleagues has found that applying a conditioning stimulus to M1 prior to a test stimulus of the other M1 can result in inhibition of the MEP amplitude, a phenomenon known as short interval interhemispheric inhibition (SIHI)28. A number of TMS studies using this approach have also shown that M1 is strongly interconnected with the contralateral M1, ventral premotor cortex (PMv), dorsal premotor cortex (PMd), supplementary motor area (SMA), pre-SMA, primary sensory cortex (S1), dorsolateral prefrontal cortex (DLPFC), and posterior parietal cortex (PPC) at rest27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42. Interestingly, the effect of stimulation from these cortical areas on motor cortical excitability are anatomically, temporally, and functionally specific to the ongoing brain activity during the preparation of a movement (state- and context-dependent43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,69). However, very few studies using dual-site TMS have characterized patterns of functional cortico-cortical connectivity with motor and cognitive impairments in patients with brain disorders70,71,72. This affords opportunities to develop new methods for assessing and treating motor and cognitive disorders.
Using this technique, it also has been found that repeated pairs of cortical TMS applied to cortical areas interconnected with M1 such as contralateral M168,69,70, PMv76,77,78, SMA71, and PPC80,81,82 can induce changes in synaptic efficiency in specific neural pathways based on the Hebbian principle of associative plasticity83,84,85,86 and enhance behavioral performance72,73,74. Still, few studies have used this approach to study circuit and plasticity dysfunction in neurological disorders2,75,76,77,78,79,80,81,82,83,84,90,91,92,93,94,95,96. It remains to be shown whether strengthening functionally specific neural pathways with TMS can restore activity in dysfunctional circuits, or whether the prospective strengthening of intact circuity can augment resilience97 in brain networks supporting motor and cognitive function across the lifespan and in disease. The lack of fundamental understanding of the neural mechanisms underlying neurological disorders and effects of stimulation on interconnected dysfunctional brain networks limits current treatment.
Despite its capability, TMS has yet to become a standard part of the armamentarium of neuroscience and clinical tools for understanding brain-behavior relations, pathophysiology of brain disorders, and the effectiveness of treatment. Therefore, to realize its potential and support its large-scale application, standardizing TMS methods is important because it is more likely to increase the rigor of future TMS experiments and reproducibility across independent laboratories. This article outlines how TMS can be used to both measure and manipulate functional interactions. Here, we describe this technique in the motor system (e.g., parieto-motor pathway44) by measuring TMS-based output measures (e.g., MEPs), where the method is best understood. However, it is important to note that this protocol also can be adapted to target functional coupling of other subcortical85, cerebellar86,87, and cortical areas.73,74,88 In addition, neuroimaging techniques such as EEG89,90,91 and fMRI92,93 can be used to assess the TMS-induced changes in activity and connectivity26,94. We conclude by proposing that the study of the functional involvement of circuit-level cortical connectivity with these TMS methods in both health and disease makes it possible to develop targeted diagnoses and innovative therapies based on more sophisticated network models of brain-behavior relations.

<table><tbody><tr><td>Alpha B.I. D50 coil (coated)</td><td>Magstim</td><td></td><td>50mm coil</td></tr><tr><td>BrainSight 2.0 Software</td><td>Rogue Research</td><td></td><td>Neuronavigation software</td></tr><tr><td>BrainSight frameless Stereotactic System</td><td>Rogue Research</td><td></td><td>Neuronavigation equiptment</td></tr><tr><td>D70&lt;sup&gt;2&lt;/sup&gt; Coil</td><td>Magstim</td><td></td><td>70mm coil</td></tr><tr><td>Discovery MR750</td><td>General Electric</td><td></td><td>3.0T MRI machine</td></tr><tr><td>Disposable Earplugs</td><td>3M</td><td></td><td>Foam earplugs</td></tr><tr><td>ECG Electrodes 30mm x 24mm</td><td>Coviden-Kendall</td><td>H124SG</td><td>Disposable electrodes</td></tr><tr><td>Four Channel Isolated Amplifier</td><td>Intronix Technologies Corporation</td><td>2024F</td><td>EMG amplifier</td></tr><tr><td>gGAMMAcap</td><td>g.tec Medical Engineering</td><td></td><td>EEG head cap</td></tr><tr><td>Micro1401-3</td><td>Cambridge Electronic Design</td><td></td><td>Scientific data recorder and processing machine</td></tr><tr><td>Nuprep Skin Prep Gel</td><td>Weaver and Company</td><td></td><td>Skin prep abrasive gel</td></tr><tr><td>Signal v.7</td><td>Cambridge Electronic Design</td><td></td><td>Data acquisition and analysis software</td></tr><tr><td>The Magstim BiStim&lt;sup&gt;2&lt;/sup&gt;</td><td>Magstim</td><td></td><td>Transcranial magnetic stimulator (two 200&lt;sup&gt;2&lt;/sup&gt; units)</td></tr></tbody></table>

measuring and manipulating functionally specific neural pathways in the human motor system with transcranial magnetic stimulation

Understanding interactions between brain areas is important for the study of goal-directed behavior. Functional neuroimaging of brain connectivity has provided important insights into fundamental processes of the brain like cognition, learning, and motor control. However, this approach cannot provide causal evidence for the involvement of brain areas of interest. Transcranial magnetic stimulation (TMS) is a powerful, noninvasive tool for studying the human brain that can overcome this limitation by transiently modifying brain activity. Here, we highlight recent advances using a paired-pulse, dual-site TMS method with two coils that causally probes cortico-cortical interactions in the human motor system during different task contexts. Additionally, we describe a dual-site TMS protocol based on cortical paired associative stimulation (cPAS) that transiently enhances synaptic efficiency in two interconnected brain areas by applying repeated pairs of cortical stimuli with two coils. These methods can provide a better understanding of the mechanisms underlying cognitive-motor function as well as a new perspective on manipulating specific neural pathways in a targeted fashion to modulate brain circuits and improve behavior. This approach may prove to be an effective tool to develop more sophisticated models of brain-behavior relations and improve diagnosis and treatment of many neurological and psychiatric disorders.

Figure 5 shows the size of an exemplar MEP response elicited in the FDI muscle by TMS for an unconditioned test stimuli (TS alone to M1, blue trace) or conditioned stimuli from PPC (CS-TS, red trace) while the participant was at rest (top panel) or planning a goal-directed grasping action to an object (bottom panel). At rest, the PPC exerts an inhibitory influence on ipsilateral M1, as shown by the decrease in MEP amplitudes potentiated by a subthreshold CS delivered over PPC 5 ms before a s...

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Measuring and Manipulating Functionally Specific Neural Pathways in the Human Motor System with Transcranial Magnetic Stimulation

This article describes new approaches to measure and strengthen functionally specific neural pathways with transcranial magnetic stimulation. These advanced noninvasive brain stimulation methodologies can provide new opportunities for the understanding of brain-behavior relations and development of new therapies to treat brain disorders.

Understanding interactions between brain areas is important for the study of goal-directed behavior. Functional neuroimaging of brain connectivity has ...

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Research

JoVE Journal

Neuroscience

9.1K Views.  University of Michigan. Deze techniek geeft inzicht in hoe hersencircuits misgaan, bij psychiatrische en neurologische aandoeningen. En hoe we hersenactiviteit kunnen manipuleren om deze disfunctionele circuits te herstellen om gedrag te verbeteren. Door de prikkelbaarheid en circuits van de hersenen direct te activeren en te remmen, maakt deze techniek het mogelijk om neurowetenschappelijke focus van observatie naar oorzakelijk verband te verschuiven en biedt een dieper begrip van de hersenen en het gedrag.N...

Video: Measuring and Manipulating Functionally Specific Neural Pathways in the Human Motor System with Transcranial Magnetic Stimulation

Transcranial Direct Current Stimulation and Simultaneous  Functional Magnetic Resonance Imaging

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that uses weak electrical currents administered to the scalp to manipulate cortical excitability and, consequently, behavior and brain function. In the last decade, numerous studies have addressed short-term and long-term effects of tDCS on different measures of behavioral performance during motor and cognitive tasks, both in healthy individuals and in a number of different patient populations. So far, however, little is known about the neural underpinnings of tDCS-action in humans with regard to large-scale brain networks. This issue can be addressed by combining tDCS with functional brain imaging techniques like functional magnetic resonance imaging (fMRI) or electroencephalography (EEG).
In particular, fMRI is the most widely used brain imaging technique to investigate the neural mechanisms underlying cognition and motor functions. Application of tDCS during fMRI allows analysis of the neural mechanisms underlying behavioral tDCS effects with high spatial resolution across the entire brain. Recent studies using this technique identified stimulation induced changes in task-related functional brain activity at the stimulation site&#160;and also in more distant brain regions, which were associated with behavioral improvement. In addition, tDCS administered during resting-state fMRI allowed identification of widespread changes in whole brain functional connectivity.
Future studies using this combined protocol should yield new insights into the mechanisms of tDCS action in health and disease and new options for more targeted application of tDCS in research and clinical settings. The present manuscript describes this novel technique in a step-by-step fashion, with a focus on technical aspects of tDCS administered during fMRI.

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique. It has successfully been used in basic research and clinical settings to modulate brain function in humans. This article describes the implementation of tDCS and simultaneous functional magnetic resonance imaging (fMRI), to investigate the neural basis of tDCS effects.

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that uses weak electrical currents administered to the scalp ...

Behavior

Transcranial Magnetic Stimulation for Investigating Causal Brain-behavioral Relationships and their Time Course

Transcranial magnetic stimulation (TMS) is a safe, non-invasive brain stimulation technique that uses a strong electromagnet in order to temporarily disrupt information processing in a brain region, generating a short-lived &#8220;virtual lesion.&#8221; Stimulation that interferes with task performance indicates that the affected brain region is necessary to perform the task normally. In other words, unlike neuroimaging methods such as functional magnetic resonance imaging (fMRI) that indicate correlations between brain and behavior, TMS can be used to demonstrate causal brain-behavior relations. Furthermore, by varying the duration and onset of the virtual lesion, TMS can also reveal the time course of normal processing. As a result, TMS has become an important tool in cognitive neuroscience. Advantages of the technique over lesion-deficit studies include better spatial-temporal precision of the disruption effect, the ability to use participants as their own control subjects, and the accessibility of participants. Limitations include concurrent auditory and somatosensory stimulation that may influence task performance, limited access to structures more than a few centimeters from the surface of the scalp, and the relatively large space of free parameters that need to be optimized in order for the experiment to work. Experimental designs that give careful consideration to appropriate control conditions help to address these concerns. This article illustrates these issues with TMS results that investigate the spatial and temporal contributions of the left supramarginal gyrus (SMG) to reading.

Transcranial magnetic stimulation (TMS) is a technique for non-invasively disrupting neural information processing and measuring its effect on behavior. When TMS interferes with a task, it indicates that the stimulated brain region is necessary for normal task performance, allowing one to systematically relate brain regions to cognitive functions.

Transcranial magnetic stimulation (TMS) is a safe, non-invasive brain stimulation technique that uses a strong electromagnet in order to temporarily ...

Combining Transcranial Magnetic Stimulation and fMRI to Examine the Default Mode Network

The default mode network is a group of brain regions that are active when an individual is not focused on the outside world and the brain is at "wakeful rest."1,2,3 It is thought the default mode network corresponds to self-referential or "internal mentation".2,3
It has been hypothesized that, in humans, activity within the default mode network is correlated with certain pathologies (for instance, hyper-activation has been linked to schizophrenia 4,5,6 and autism spectrum disorders 7 whilst hypo-activation of the network has been linked to Alzheimer's and other neurodegenerative diseases 8). As such, noninvasive modulation of this network may represent a potential therapeutic intervention for a number of neurological and psychiatric pathologies linked to abnormal network activation. One possible tool to effect this modulation is Transcranial Magnetic Stimulation: a non-invasive neurostimulatory and neuromodulatory technique that can transiently or lastingly modulate cortical excitability (either increasing or decreasing it) via the application of localized magnetic field pulses.9
In order to explore the default mode network's propensity towards and tolerance of modulation, we will be combining TMS (to the left inferior parietal lobe) with functional magnetic resonance imaging (fMRI). Through this article, we will examine the protocol and considerations necessary to successfully combine these two neuroscientific tools.

In this article, we examine the methodology and considerations relevant to the combination of TMS and fMRI to examine the effects of brain stimulation on the default network.

The default mode network is a group of brain regions that are active when an individual is not focused on the outside world and the brain is at "wakeful ...

Multifunctional Setup for Studying Human Motor Control Using Transcranial Magnetic Stimulation, Electromyography, Motion Capture, and Virtual Reality

The study of neuromuscular control of movement in humans is accomplished with numerous technologies. Non-invasive methods for investigating neuromuscular function include transcranial magnetic stimulation, electromyography, and three-dimensional motion capture. The advent of readily available and cost-effective virtual reality solutions has expanded the capabilities of researchers in recreating &#8220;real-world&#8221; environments and movements in a laboratory setting. Naturalistic movement analysis will not only garner a greater understanding of motor control in healthy individuals, but also permit the design of experiments and rehabilitation strategies that target specific motor impairments (e.g. stroke). The combined use of these tools will lead to increasingly deeper understanding of neural mechanisms of motor control. A key requirement when combining these data acquisition systems is fine temporal correspondence between the various data streams. This protocol describes a multifunctional system&#8217;s overall connectivity, intersystem signaling, and the temporal synchronization of recorded data. Synchronization of the component systems is primarily accomplished through the use of a customizable circuit, readily made with off the shelf components and minimal electronics assembly skills.

Transcranial magnetic stimulation, electromyography, and 3D motion capture are commonly used non-invasive techniques for investigating neuromuscular function in humans. In this paper, we describe a protocol that synchronously samples data generated by all three of these tools along with the unique addition of virtual reality stimulus presentation and feedback.

The study of neuromuscular control of movement in humans is accomplished with numerous technologies. Non-invasive methods for investigating neuromuscular ...

Utilizing Transcranial Magnetic Stimulation to Study the Human Neuromuscular System

Transcranial magnetic stimulation (TMS) has been in use for more than 20 years 1, and has grown exponentially in popularity over the past decade. While the use of TMS has expanded to the study of many systems and processes during this time, the original application and perhaps one of the most common uses of TMS involves studying the physiology, plasticity and function of the human neuromuscular system. Single pulse TMS applied to the motor cortex excites pyramidal neurons transsynaptically 2 (Figure 1) and results in a measurable electromyographic response that can be used to study and evaluate the integrity and excitability of the corticospinal tract in humans 3. Additionally, recent advances in magnetic stimulation now allows for partitioning of cortical versus spinal excitability 4,5. For example, paired-pulse TMS can be used to assess intracortical facilitatory and inhibitory properties by combining a conditioning stimulus and a test stimulus at different interstimulus intervals 3,4,6-8. In this video article we will demonstrate the methodological and technical aspects of these techniques. Specifically, we will demonstrate single-pulse and paired-pulse TMS techniques as applied to the flexor carpi radialis (FCR) muscle as well as the erector spinae (ES) musculature. Our laboratory studies the FCR muscle as it is of interest to our research on the effects of wrist-hand cast immobilization on reduced muscle performance6,9, and we study the ES muscles due to these muscles clinical relevance as it relates to low back pain8. With this stated, we should note that TMS has been used to study many muscles of the hand, arm and legs, and should iterate that our demonstrations in the FCR and ES muscle groups are only selected examples of TMS being used to study the human neuromuscular system.

Transcranial magnetic stimulation (TMS) is a non-invasive tool to gain insight on the physiology and function of the human nervous system. Here, we present our TMS techniques to study cortical excitability of the upper limb and lumbar musculature.

Transcranial magnetic stimulation (TMS) has been in use for more than 20 years 1, and has grown exponentially in popularity over the past decade.  While ...

Medicine

The Use of Magnetic Resonance Spectroscopy as a Tool for the Measurement of Bi-hemispheric Transcranial Electric Stimulation Effects on Primary Motor Cortex Metabolism

Transcranial direct current stimulation (tDCS) is a neuromodulation technique that has been increasingly used over the past decade in the treatment of neurological and psychiatric disorders such as stroke and depression. Yet, the mechanisms underlying its ability to modulate brain excitability to improve clinical symptoms remains poorly understood 33. To help improve this understanding, proton magnetic resonance spectroscopy (1H-MRS) can be used as it allows the in vivo quantification of brain metabolites such as &#947;-aminobutyric acid (GABA) and glutamate in a region-specific manner 41. In fact, a recent study demonstrated that 1H-MRS is indeed a powerful means to better understand the effects of tDCS on neurotransmitter concentration 34. This article aims to describe the complete protocol for combining tDCS (NeuroConn MR compatible stimulator) with 1H-MRS at 3 T using a MEGA-PRESS sequence. We will describe the impact of a protocol that has shown great promise for the treatment of motor dysfunctions after stroke, which consists of bilateral stimulation of primary motor cortices 27,30,31. Methodological factors to consider and possible modifications to the protocol are also discussed.

This article aims to describe a basic protocol for combining transcranial direct current stimulation (tDCS) with proton magnetic resonance spectroscopy (1H-MRS) measurements to investigate the effects of bilateral stimulation on primary motor cortex metabolism.

Transcranial direct current stimulation (tDCS) is a neuromodulation technique that has been increasingly used over the past decade in the treatment of ...

Effects of Transcranial Alternating Current Stimulation on the Primary Motor Cortex by Online Combined Approach with Transcranial Magnetic Stimulation

Transcranial Alternating Current Stimulation (tACS) is a neuromodulatory technique able to act through sinusoidal electrical waveforms in a specific frequency and in turn modulate ongoing cortical oscillatory activity. This neurotool allows the establishment of a causal link between endogenous oscillatory activity and behavior. Most of the tACS studies have shown online effects of tACS. However, little is known about the underlying action mechanisms of this technique because of the AC-induced artifacts on Electroencephalography (EEG) signals. Here we show a unique approach to investigate online physiological frequency-specific effects of tACS of the primary motor cortex (M1) by using single pulse Transcranial Magnetic Stimulation (TMS) to probe cortical excitability changes. In our setup, the TMS coil is placed over the tACS electrode while Motor Evoked Potentials (MEPs) are collected to test the effects of the ongoing M1-tACS. So far, this approach has mainly been used to study the visual and motor systems. However, the current tACS-TMS setup can pave the way for future investigations of cognitive functions. Therefore, we provide a step-by-step manual and video guidelines for the procedure.

Transcranial Alternating Current Stimulation (tACS) allows the modulation of cortical excitability in a frequency-specific fashion. Here we show a unique approach which combines online tACS with single pulse Transcranial Magnetic Stimulation (TMS) in order to "probe" cortical excitability by means of Motor Evoked Potentials.

Transcranial Alternating Current Stimulation (tACS) is a neuromodulatory technique able to act through sinusoidal electrical waveforms in a specific ...

Combined Transcranial Magnetic Stimulation and Electroencephalography of the Dorsolateral Prefrontal Cortex

Transcranial magnetic stimulation (TMS) is a non-invasive method that produces neural excitation in the cortex by means of brief, time-varying magnetic field pulses. The initiation of cortical activation or its modulation depends on the background activation of the neurons of the cortical region activated, the characteristics of the coil, its position and its orientation with respect to the head. TMS combined with simultaneous electrocephalography (EEG) and neuronavigation (nTMS-EEG) allows for the assessment of cortico-cortical excitability and connectivity in almost all cortical areas in a reproducible manner. This advance makes nTMS-EEG a powerful tool that can accurately assess brain dynamics and neurophysiology in test-retest paradigms that are required for clinical trials. Limitations of this method include artifacts that cover the initial brain reactivity to stimulation. Thus, the process of removing artifacts may also extract valuable information. Moreover, the optimal parameters for dorsolateral prefrontal (DLPFC) stimulation are not fully known and current protocols utilize variations from the motor cortex (M1) stimulation paradigms. However, evolving nTMS-EEG designs hope to address these issues. The protocol presented here introduces some standard practices for assessing neurophysiological functioning from stimulation to the DLPFC that can be applied in patients with treatment resistant psychiatric disorders that receive treatment such as transcranial direct current stimulation (tDCS), repetitive transcranial magnetic stimulation (rTMS), magnetic seizure therapy (MST) or electroconvulsive therapy (ECT).

The protocol presented here is for TMS-EEG studies utilizing intracortical excitability test-retest design paradigms. The intent of the protocol is to produce reliable and reproducible cortical excitability measures for assessing neurophysiological functioning related to therapeutic interventions in the treatment of neuropsychiatric diseases such as major depression.

Transcranial magnetic stimulation (TMS) is a non-invasive method that produces neural excitation in the cortex by means of brief, time-varying magnetic ...

Bilateral Assessment of the Corticospinal Pathways of the Ankle Muscles Using Navigated Transcranial Magnetic Stimulation

Distal leg muscles receive neural input from motor cortical areas via the corticospinal tract, which is one of the main motor descending pathway in humans and can be assessed using transcranial magnetic stimulation (TMS). Given the role of distal leg muscles in upright postural and dynamic tasks, such as walking, a growing research interest in the assessment and modulation of the corticospinal tracts relative to the function of these muscles has emerged in the last decade. However, methodological parameters used in previous work have varied across studies making the interpretation of results from cross-sectional and longitudinal studies less robust. Therefore, use of a standardized TMS protocol specific to the assessment of leg muscles&#39; corticomotor response (CMR) will allow for direct comparison of results across studies and cohorts. The objective of this paper is to present a protocol that provides the flexibility to simultaneously assess the bilateral CMR of two main ankle antagonistic muscles, the tibialis anterior and soleus, using single pulse TMS with a neuronavigation system. The present protocol is applicable while the examined muscle is either fully relaxed or isometrically contracted at a defined percentage of maximum isometric voluntary contraction. Using each subject&#39;s structural MRI with the neuronavigation system ensures accurate and precise positioning of the coil over the leg cortical representations during assessment. Given the inconsistency in CMR derived measures, this protocol also describes a standardized calculation of these measures using automated algorithms. Though this protocol is not conducted during upright postural or dynamic tasks, it&#160;can be used to assess bilaterally any pair of leg muscles, either antagonistic or synergistic, in both neurologically intact and impaired subjects.

The present protocol describes the simultaneous, bilateral assessment of the corticomotor response of the tibialis anterior and soleus during rest and tonic voluntary activation using a single pulse transcranial magnetic stimulation and neuronavigation system.

Distal leg muscles receive neural input from motor cortical areas via the corticospinal tract, which is one of the main motor descending pathway in humans ...

Non-Invasive Modulation and Robotic Mapping of Motor Cortex in the Developing Brain

Mapping the motor cortex with transcranial magnetic stimulation (TMS) has potential to interrogate motor cortex physiology and plasticity but carries unique challenges in children. Similarly, transcranial direct current stimulation (tDCS) can improve motor learning in adults but has only recently been applied to children. The use of tDCS and emerging techniques like high&#8211;definition tDCS (HD-tDCS) require special methodological considerations in the developing brain. Robotic TMS motor mapping may confer unique advantages for mapping, particularly in the developing brain. Here, we aim to provide a practical, standardized approach for two integrated methods capable of simultaneously exploring motor cortex modulation and motor maps in children. First, we describe a protocol for robotic TMS motor mapping. Individualized, MRI-navigated 12x12 grids centered on the motor cortex guide a robot to administer single-pulse TMS. Mean motor evoked potential (MEP) amplitudes per grid point are used to generate 3D motor maps of individual hand muscles with outcomes including map area, volume, and center of gravity. Tools to measure safety and tolerability of both methods are also included. Second, we describe the application of both tDCS and HD-tDCS to modulate the motor cortex and motor learning. An experimental training paradigm and sample results are described. These methods will advance the application of non-invasive brain stimulation in children.

We demonstrate protocols for the modulation (tDCS, HD-tDCS) and mapping (robotic TMS) of the motor cortex in children.

Mapping the motor cortex with transcranial magnetic stimulation (TMS) has potential to interrogate motor cortex physiology and plasticity but carries ...

Measuring and Manipulating Functionally Specific Neural Pathways in the Human Motor System with Transcranial Magnetic Stimulation

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