Pantelis Lioumis has been supported by an HUS VTR grant (TYH2022224), Salla Autti by the P&#228;ivikki and Sakari Sohlberg Foundation, and Hanna Renvall by the Paulo Foundation and Academy of Finland (grant 321460).

This study was approved by the Hospital District of Helsinki and Uusimaa ethics committee. Informed consent to participate was obtained before the procedure from each subject.
1. Preparation of the structural images
<ol>
	<li>Record a high-resolution T1-weighted structural MRI of the whole head for each subject (preferably with a 0 mm slice gap and 1 mm slice thickness). Acquire the images as specified in the neuronavigation system&#39;s instructions.</li>
	<li>Upload the MR images to the navigation system in its preferred format (typically DICOM or NifTI).</li>
	<li>Go through the MR images, and check for any errors (e.g., blurry cardinal points, noise disturbances, or misplacements in the 3D model reconstruction).</li>
	<li>Find the cardinal points (i.e., the middle of the ridge in each earlobe and the nasion) in the axial, sagittal, and coronal MRI planes, mark them by pressing the crosshair function in the planes, and choose the exact spot by clicking the left button of the mouse. Then, press the &#34;add landmarks&#34; button with the mouse.</li>
	<li>Insert parcellations of the brain areas of interest (e.g., pinpointed by other functional methods [MEG, fMRI, PET] or based on MRI databases or atlases)21. Choose the &#34;overlay image&#34; function.</li>
</ol>
2. Preparation for neuronavigation
<ol>
	<li>Check that the subject does not have any metal items (e.g., earrings) in the head and neck area, and ensure that there are no absolute contraindications such as intracranial metal clips.</li>
	<li>Place the subject in the patient chair. Adjust the chair so that the subject is sitting comfortably, with the neck, hands, and legs relaxed. Adjust the chair height so that the operator can comfortably stimulate the whole hemisphere under investigation.</li>
	<li>Place the head tracker so that it is stabilized during the stimulation session (with a sticker or a strap) and does not block the TMS coil from being moved freely over the head, especially over the temporal areas. The tracker may be situated slightly right on the forehead if the left hemisphere is stimulated and vice versa if the right hemisphere is stimulated to ensure that the anterior frontal lobe areas can be stimulated.</li>
	<li>Co-register the subject&#39;s head to the MRI-reconstructed 3D head model. Use a digitizing pen on the participant&#39;s head to mark the cardinal points (nasion, pre-auricular points) that were selected on the MRIs. Digitize additional points over the whole skull surface to reduce the final registration error. Place the digitizing pen over each highlighted spot on the 3D head model, and press the left pedal when the spot starts blinking on the navigator screen.</li>
	<li>Validate the registration, even if the overall error is acceptable (below 4 mm). Touch the subject&#39;s head with the tip of the digitizing pen. Double-check visually that the pen is at the analogous place on the surface of the 3D MRI-based model. If its position does not correspond to the point in the MRI, repeat steps 2.1-2.4.</li>
	<li>Ensure that both the subject and the operator wear ear protection before starting the stimulation.</li>
</ol>
3. Defining the hot spot and motor threshold for M1 stimulation
<ol>
	<li>For determining the resting motor threshold (rMT), choose a distal hand muscle (e.g., the abductor pollicis brevis [APB]) from the right hand. 
	NOTE. The motor threshold is used to define the initial stimulation intensity, which may be subsequently changed as explained below. Thus, any distal hand muscle can be used for this purpose.</li>
	<li>Place a single-use gel electrode (diameter: ~30 mm) over the right APB (the belly of the muscle), and another on the middle of the thumb (tendon). Place the ground electrode near the wrist (or follow the manufacturer&#39;s guidelines).</li>
	<li>Connect the electrodes to the electromyography (EMG)&#160;amplifier, and verify that the APB is at rest by observing the continuous EMG&#160;signal. Change the position of the hand if the recorded muscle cannot be easily relaxed.</li>
	<li>Find the cortical hot spot for determining the APB motor threshold. Starting from the motor hand knob area22, deliver a few TMS pulses, and continue by moving and rotating the coil until APB motor evoked potentials (MEPs) appear. 
	NOTE: Usually, motor representations of the thumb are located perpendicular to the lateral wall of the hand knob.
	<ol>
		<li>Choose a TMS intensity that evokes MEPs of around 200-500 &#181;V. Optimize the coil location and orientation by slightly changing its angle to evoke the maximum MEPs.</li>
	</ol>
	</li>
	<li>Save the optimal coil location in the neuronavigation software by right-clicking over the pulse number corresponding to the hot spot site and choosing the option to repeat the stimulus. Repeat the stimuli, and apply an automatic threshold hunting algorithm23 by right-clicking on the hot spot and choosing the option of motor threshold from the neuronavigation software.</li>
	<li>If these options are not available, apply the rule that a TMS pulse needs to evoke 10 MEPs (&#8805;50 &#181;V) out of 20 trials24.</li>
</ol>
4. Baseline naming of images
<ol>
	<li>Familiarize the subject with the images before the baseline object naming task11,12. Print the images (or show them in digital format), and let the subject practice before the session starts (the subject could also practice at home).
	<ol>
		<li>Use properly standardized normalized color images (e.g., from the Bank of Standardized Stimuli25; Supplementary Figure 1).</li>
		<li>Use only images that are frequently seen in an everyday environment, have a minimal number of synonyms, and have high name agreement.</li>
	</ol>
	</li>
	<li>If available, attach an accelerometer on the skin above the larynx and the vocal cords to record the speech onset, as explained in Vitikainen et al.26.</li>
	<li>Show the images to the subject one by one and ask them to name the images aloud without stimulation.
	<ol>
		<li>Present the images to the subject on a screen placed at a 0.5-1 m distance.</li>
		<li>Use a display time of 700-1,000 ms per image.</li>
	</ol>
	</li>
	<li>Adjust the inter-picture interval (IPI) to make the task slightly challenging for each subject (e.g., start with 2,500 ms, and vary between 1,500-4,000 ms).
	<ol>
		<li>If many errors occur during the baseline naming task, increase the IPI in steps of 200-300 ms. If the task is too easy, decrease the IPI in steps of 200-300 ms.</li>
	</ol>
	</li>
	<li>For the actual speech mapping session with nrTMS, omit the images that during the baseline testing were not trained adequately, not named correctly, not named clearly, not articulated correctly, named with delay or hesitance, or seemed difficult for the subject.</li>
	<li>Run the baseline naming task three times, and repeat steps 4.3-4.5 if performance is not satisfactory.</li>
</ol>
5. Speech cortical mapping
<ol>
	<li>Vary the stimulation intensity by increasing/decreasing it in steps of 1% of the stimulator&#39;s output so that each target area receives the same induced electric field (E-field), as defined for the rMT of the hand muscles at the cortical hand motor hotspot. Usually, higher intensities need to be applied for parietal than for frontotemporal targets to reach similar cortical E-fields as for the rMT hotspot.
	<ol>
		<li>Lower the intensity when stimulating cortical structures located closer to the head surface (E-field above the pre-defined rMT E-field).</li>
	</ol>
	</li>
	<li>Check before starting the stimulation that the induced E-field values are approximately similar (with a 2-3 V/m difference) in the different speech-related areas in both hemispheres.
	<ol>
		<li>Adjust the cortical depth (peeling depth) if needed.</li>
		<li>Ensure that the coil center is not in the air.</li>
	</ol>
	</li>
	<li>Start with a default picture-to-TMS interval (PTI) of 300 ms, or use a 0-400 ms PTI; a PTI above 150 ms is preferred to optimize the overlap of stimulation with language processing.</li>
	<li>Start with five pulses at a 5 Hz stimulation rate. Start from a cortical area not related to speech processing so that the subject gets used to the sensation induced by the stimulation. Then, move the coil to the expected speech-related areas.</li>
	<li>Keep the coil in the same position until the pulse train is over and the subject&#39;s naming is completed.</li>
	<li>Focus on the subject&#39;s performance as described below.
	<ol>
		<li>If no error is observed, move on to the next locus.</li>
		<li>If an error, or even a hesitation, is observed, continue stimulating that site for an additional two to three nrTMS trains, and then move on. Keep the site in mind for possible later re-stimulation.</li>
		<li>Make small coil adjustments when even a slight error is detected (e.g., minor hesitation or a louder voice during the naming due to an increased effort) to provoke clearer errors.</li>
		<li>Avoid repeating stimulation on the same site for more than five consecutive trains. Continue with other cortical sites, and revisit the site later.</li>
		<li>If repeated errors appear at several stimulated locations, lift the coil in the air above the scalp, and check if errors still occur.</li>
		<li>If errors still occur, take a break, and wait until the naming returns to normal. 
		&#8203;NOTE. Repeated naming errors unrelated to the stimulation may be common if speech-related areas are affected by a tumor or other lesion.</li>
		<li>Stimulate in blocks of 7-10 min (maximum) continuously, and have 2-5 min breaks in between. 
		NOTE: Errors become more common with long stimulations and if the subject is tired.</li>
	</ol>
	</li>
	<li>Stimulate all the possibly related anatomical areas (e.g., IFG, STG, SMG, middle temporal, precentral, postcentral, and angular gyri, and the prefrontal cortex) to obtain as many control responses as possible.</li>
	<li>If feasible and/or clinically supported, stimulate both hemispheres. Stimulate carefully inside and around the tumor region or the estimated location of the lesion even if those regions do not belong to the classical speech-related areas (for tumor and epilepsy patients).
	<ol>
		<li>Investigate cortical areas that are located away from the lesion site to identify possible spatial shifts in the language areas due to plastic changes or the mass effect, especially in patients with large lesions.</li>
	</ol>
	</li>
	<li>Reduce the TMS intensity in steps of 2%-5% of the maximum stimulator output if the mapping induces pain or discomfort.</li>
	<li>Stop the measurement if the induced pain or discomfort are not tolerated by the subject.</li>
</ol>
6. Strategy when no naming errors occur
<ol>
	<li>Terminate the stimulation, and change stimulation parameters.</li>
	<li>Decrease the IPI in steps of 200 ms from the default value (e.g., from 2,500 ms to 2,300 ms).</li>
	<li>Change the frequency of pulse delivery from 5 Hz to 7 Hz. Change the interval between the onset of the presented image and the rTMS (currently, there is no consensus on whether to increase or decrease it). Increase the stimulation intensity (without evoking discomfort).</li>
</ol>
7. Off-line analysis of the evoked naming errors
<ol>
	<li>Collaborate with an expert (e.g., a neuropsychologist), who should optimally be present in the operating room.</li>
	<li>Double-check the evoked naming errors by observing the coil positioning and possible pain interference from the video recordings.</li>
	<li>Classify the errors according to Corina et al.27 (e.g., anomia, semantic and phonological paraphasia, performance errors).
	<ol>
		<li>If a particular type of error repeats itself in the baseline video, do not consider it as an error when analyzing the stimulation session videos.</li>
	</ol>
	</li>
	<li>If an object is named after the rTMS train, consider this as a delay or a no-error; check also for possible discomfort of the subject during the pulse delivery.</li>
	<li>If the subject cannot name a given object although the tongue, lips, and jaws are moving, record a no-response error.</li>
	<li>If an image is named differently in each session, discard it.</li>
	<li>If unsure, control the performance of the neighboring stimulation site or the effect of the stimulation of the other hemisphere with the same image.</li>
</ol>

P.L. has been a consultant to Nexstim Ltd. for motor and speech cortical mapping.

Here, a protocol is presented for nrTMS SCM, which enables practically complete cortical noninvasive mapping of the most important hubs of the speech and language network. Its main advantage is that it can non-invasively simulate the DCS mapping during awake craniotomy30 or extraoperatively29 (see Figure 2). Moreover, it can be applied to language cortical network studies in healthy populations31 and in patients with diseases that are not amenable to surgery32. nrTMS for SCM may also be applied to develop neurorehabilitation strategies such as target selection (e.g., after stroke). The induction of plasticity in speech-related cortical representations by DCS prior to surgery has been studied33 to increase the extent of resection34. The possibilities of nrTMS SCM in such studies should be examined.
In the present results, a relatively large area, including classical speech-related areas and the pre-SMA, was repeatedly stimulated at three different PTIs. Each PTI showed different sensitivity and specificity to errors, but also demonstrated the well-known response variability in non-invasive brain stimulations35. Most errors were induced by the stimulation of the IFG, STG, pre-SMA, and along the frontal aslant tract36. This highlights the power of nrTMS SCM; specifically, in comparison to DCS, the stimulation can be quite flexibly targeted to several areas. We have observed that changing the PTI and recording many sessions does not clearly speed up the reaction times26,29, which would be associated with a learning effect.
The protocol highlights different parameters that can affect the accuracy of nrTMS SCM. The results can be sensitive to the choices made by the TMS operator; the present paper aims to provide a standard guideline with well-tested stimulation parameters. High specificity results from an appropriate choice of several different parameters, including the ISI, PTI, coil location, and rTMS frequency. These parameters affect the specificity of the induced errors, which reflect the functions in the underlying cortical areas; the&#160;parameter selection needs to be based on current knowledge on the neurobiology of language.
The images for the naming task should be selected so that they do not induce erroneous naming by themselves (Supplementary Figure&#160;1). Here, the images were chosen from a standardized image bank and controlled for various naming parameters25,37. For example, the pool of images was restricted to items with similar complexity and frequency in everyday use, as well as high name agreement. The choice of images can vary based on the needs of each surgical center38, the population under investigation39,&#160;the native language of the tested subject40,41 and the used task42. As presented in the protocol, the baseline image selection is finally individualized for each subject, as on-spot naming is subjective.
The stimulation frequency needs to be defined individually, because it may determine the distribution of errors during navigated transcranial magnetic brain stimulation43. The presented choice, 4-8 Hz, is based on the rTMS work by Epstein et al.44. The initial stimulation frequency is set to 5 Hz. If no errors are detected, the stimulation frequency is increased to 7 Hz. Higher frequencies may reduce nrTMS-induced pain and increase the specificity of naming errors45. Higher frequencies also have the advantage of limiting the pulses to a short and more specific time interval. They may, however, affect functions related to, for example, speech motor execution44,46, which are not the main target of the present protocol.
It is recommended to vary the PTI between 150-400 ms. This is an important time window for word retrieval during the object naming task28,47. The protocol aims at speech specificity by avoiding the interference of basic visual processing, which occurs during the first 150 ms after image presentation and may affect object naming but is unrelated to speech production. The recommended upper limit for the PTI is based on typical response latencies in picture naming in the same subject28,48, and individual variation in the optimal values between subjects can be expected (see Figure 1). The PTI selection should ideally be based on personalized measures, although this may be logistically demanding in a clinical setting. Helsinki University Hospital protocols usually start with a 300 ms PTI. It may also be useful to change the PTI based on the stimulated area12,13,49, as indicated by several language studies28,47,50. Nevertheless, PTIs outside the above-mentioned window may also induce naming errors that are useful for presurgical evaluation (for a comparative study, see Krieg et al.49 using PTIs of 0-300 ms).
The cortical speech network is widespread and varies among individuals, particularly in patients with tumors and epilepsy29,30,39. nrTMS induces language disturbance with great variability across individuals, analogous to those observed during awake craniotomy stimulations27,51. The information obtained from fMRI50, DTI52,53,54, and MEG55 can direct the nTMS user and result in a procedure that is tailored for each individual and is, thus, more specific and accurate. The objective in nrTMS SCM is to increase the specificity, reduce the number of non-responders, guide the DCS reliably, or replace it when the resources and conditions do not allow a team of highly specialized experts to perform it.&#160;In the future, multilocus TMS (mTMS) could be applied in the procedure to stimulate different parts of the cortex without physically moving the stimulation coil56.
The present protocol can be performed with several types of naming tasks42,57 or other cognitive tasks (calculations, decision making, etc.)58. The video recording can disclose crucial features of the task performance (e.g., grimaces by the subject indicating that no motor speech arrest is induced) that can go unobserved during the stimulation. The setup also allows for asking the subject about the nrTMS-induced experiences and sensations by jointly viewing the video recording. This can help in distinguishing pain-induced errors from the true effects of nrTMS. Finally, the protocol can be easily modified to different subject groups (e.g., bilingual individuals31) and to serve the needs of each surgical or research team.

During neurosurgery due to cerebral disease (e.g., epilepsy or a tumor), the extent of resection must be optimized to preserve brain regions that support critical functions. Areas vital for patient integrity and quality of life, such as language-related ones, should be characterized prior to the removal of brain tissue. Typically, they cannot be individually identified merely based on anatomical landmarks1. The functional mapping of language areas for surgical decision-making is usually done invasively by electrical direct cortical stimulation (DCS), which enables the neurosurgeon to understand the organization of the crucial cortical and subcortical structures within each patient2. Although DCS during awake surgery is considered the gold&#160;standard of cortical mapping for speech functions, it is limited by its invasiveness, methodological challenges, and the high stress it induces for both the patient and the surgical team. This protocol describes non-invasive speech cortical mapping (SCM) using navigated transcranial magnetic stimulation (navigated TMS or nTMS). Accurate non-invasive mapping aids in surgical planning, and reduces the time, costs, and risks in the operation room (OR). It also provides an alternative for those patients who are not suitable for awake craniotomy3.
Non-invasive imaging methods have already greatly benefited presurgical planning. Anatomical magnetic resonance imaging (MRI) is crucial for locating tumors and brain lesions; in neuronavigation4 and in the navigated TMS mapping5, it guides the operator to the cortical sites of interest. Diffusion-based MRI (dMRI) tractography provides detailed information on the white-matter fiber tracts that connect cortical regions5,6. During the last decade, functional imaging techniques, most notably functional MRI (fMRI) and magnetoencephalography (MEG), have been increasingly used for preoperative motor and speech cortical mapping (SCM)2,8,9. Each method brings benefits to the preoperative mapping procedure, and can, for example, provide information on the functionally related regions outside of the conventional language areas (Broca&#39;s and Wernicke&#39;s areas). fMRI has been the most commonly used method1 due to its high availability; it has been compared to DCS in the localization of speech-related areas with variable results2,10. However, although functional imaging can identify the involved brain regions, it cannot determine whether these regions are critical for the function to be preserved.
Navigated repetitive TMS (nrTMS) is nowadays used as an alternative to the aforementioned methods for preoperative non-invasive SCM11,12. nrTMS SCM is especially efficient in identifying speech-related cortical areas within the inferior frontal gyrus (IFG), superior temporal gyrus (STG), and supramarginal gyrus (SMG)11,13. An advantage of the method is that the offline analysis of the errors evoked by the stimulation allows the analyzer to be unaware of the stimulation site. It is, thus, possible to judge the error without a priori information of the cortical site&#39;s relevance to the speech network. This is enabled by a video recording, which allows the analyzer to distinguish subtle differences in errors, such as semantic and phonological paraphasia, more reliably than during the actual examination11,12. The nrTMS SCM approach currently surpasses the performance of MEG or fMRI speech mapping alone10,14, and additional functional or anatomical information may be used to fine-tune the nrTMS procedure. Preoperative mapping with nrTMS has been demonstrated to shorten operation times and reduce the required size of craniotomy and damage to the eloquent cortex15. It shortens the time of hospitalization and enables a more extensive removal of tumor tissue, thereby increasing patient survival rates15. nrTMS has been validated against intraoperative DCS mapping; specifically, the sensitivity of nrTMS in SCM is high, but its specificity remains low, with excessive false positives compared to DCS13,16.
Currently, presurgical non-invasive SCM with nrTMS can assist in patient selection for operation, help in designing the surgery, and speed up the DCS conducted during the surgery17. Here, a detailed description of how nrTMS SCM can be performed to obtain reliable speech-specific results is provided. After gaining practical experience, the suggested protocol can be tailored to best fit the patient- and site-specific demands. The protocol can be further expanded to certain targets, such as speech production (speech arrest)18,19 or visual and cognitive functions20.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Neurology surface electrodes</td>
			<td>Ambu A/S</td>
			<td>Ambu Neuroline Ground</td>
			<td></td>
		</tr>
		<tr>
			<td>Neurology surface electrodes</td>
			<td>Ambu A/S</td>
			<td>Ambu Neuroline 720</td>
			<td></td>
		</tr>
		<tr>
			<td>Off-line speech error analyzer</td>
			<td>Nexstim Ltd</td>
			<td>NexSpeech 2.1.0</td>
			<td></td>
		</tr>
		<tr>
			<td>Single patient surface electrode</td>
			<td>Ambu A/S</td>
			<td>Ambu Neuroline 700</td>
			<td></td>
		</tr>
		<tr>
			<td>Stimulator</td>
			<td>Nexstim Ltd</td>
			<td>NBS 4.3</td>
			<td></td>
		</tr>
	</tbody>
</table>

study design for navigated repetitive transcranial magnetic stimulation for speech cortical mapping

The cortical areas involved in human speech should be characterized reliably prior to surgery for brain tumors or drug-resistant epilepsy. The functional mapping of language areas for surgical decision-making is usually done invasively by electrical direct cortical stimulation (DCS), which is used to identify the organization of the crucial cortical and subcortical structures within each patient. Accurate preoperative non-invasive mapping aids surgical planning, reduces time, costs, and risks in the operating room, and provides an alternative for patients not suitable for awake craniotomy. Non-invasive imaging methods like MRI, fMRI, MEG, and PET are currently applied in presurgical design and planning. Although anatomical and functional imaging can identify the brain regions involved in speech, they cannot determine whether these regions are critical for speech. Transcranial magnetic stimulation (TMS) non-invasively excites the cortical neuronal populations by means of electric field induction in the brain. When applied in its repetitive mode (rTMS) to stimulate a speech-related cortical site, it can produce speech-related errors analogous to those induced by intraoperative DCS. rTMS combined with neuronavigation (nrTMS) enables neurosurgeons to preoperatively assess where these errors occur and to plan the DCS and the operation to preserve the language function. A detailed protocol is provided here for non-invasive speech cortical mapping (SCM) using nrTMS. The proposed protocol can be modified to best fit the patient- and site-specific demands. It can also be applied to language cortical network studies in healthy subjects or in patients with diseases that are not amenable to surgery.

A navigated transcranial magnetic stimulation system with integrated screens and cameras was used. Figure 1A-C highlights the different TMS-evoked naming errors in one subject during the task at different PTIs (180 ms, 200 ms, and 215 ms). The effect of the timing of the TMS pulses on the number of errors evoked is evident. In other words, TMS-related changes in performance were detected in different areas at different PTIs. The number of errors varied depending on the timing of the TMS pulses even at the same cortical sites, in accordance with MEG studies demonstrating the variation in the timing of activation in different speech-related cortical areas28. A comparison of the results between extraoperative DCS mapping and nrTMS with a fixed PTI at 300 ms in a patient with intractable epilepsy is shown in Figure 2. The data were obtained from a previous publication focusing on epilepsy29.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/64492/64492fig01.jpg" /> 
Figure 1: Results of an nrTMS SCM illustrated over a 3D MRI-based model from a healthy volunteer. (A) PTI of 180 ms. (B) PTI of 200 ms. (C) PTI of 215ms. In addition to the major speech-related areas, the pre-supplementary motor area (pre-SMA) was stimulated as described in the protocol (step 5.7). Most of the errors were evoked in the classical speech areas (IFG, STG, SMG), but also along the path connecting the pre-SMA and Broca&#39;s area (the close-to-midline green spots in A and B). <a href="https://www.jove.com/files/ftp_upload/64492/64492fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/64492/64492fig02.jpg" /> 
Figure 2: Comparison of the results between extraoperative DCS mapping and nrTMS with a fixed PTI at 300 ms in a patient with intractable epilepsy. (A)&#160;Extraoperative grid mapping at the age of 13. The yellow spheres represent all the electrodes on the cortex. The sites of electrode stimulation (2-5 mA) that induced motor responses of the hand and mouth (green circles), naming arrest (anomia; red circles), and interrupting sentence repetition (pink circles) are shown. (B)&#160;nrTMS SCM of the same patient at the age of 15. The sites of nrTMS-induced anomias (red dots), semantic and phonological paraphasias (yellow dots), and hesitations (white dots) are shown. The areas with highly reproducible and reliable error induction are circled. The data for this image were taken from the study of Lehtinen et al.29. <a href="https://www.jove.com/files/ftp_upload/64492/64492fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Supplementary Figure 1:&#160;Examples of images presented in the nrTMS SCM experiment (in Finnish in parentheses). (A) Hanger (Henkari). (B) Scissors (Sakset). (C) Strawberry (Mansikka). <a href="https://www.jove.com/files/ftp_upload/64492/supplemfigure1.jpg" target="_blank">Please click here to download this File.</a>

Watch this Scientific Journal Video about Study Design for Navigated Repetitive Transcranial Magnetic Stimulation for Speech Cortical Mapping at JoVE.com

Study Design for Navigated Repetitive Transcranial Magnetic Stimulation for Speech Cortical Mapping

Navigated repetitive transcranial magnetic stimulation is a highly efficient non-invasive tool for mapping speech-related cortical areas. It helps in designing brain surgery and speeds up the direct cortical stimulation conducted during the surgery. This report describes how to perform speech cortical mapping reliably for preoperative evaluation and research.

The cortical areas involved in human speech should be characterized reliably prior to surgery for brain tumors or drug-resistant epilepsy. The functional ...

study-design-for-navigated-repetitive-transcranial-magnetic

Research

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1.3K Views.  Aalto University School of Science. Navigated repetitive transcranial magnetic stimulation is a highly efficient non-invasive tool for mapping speech-related cortical areas. It helps in designing brain surgery and speeds up the direct cortical stimulation conducted during the surgery. This report describes how to perform speech cortical mapping reliably for preoperative evaluation and research. 

Video: Study Design for Navigated Repetitive Transcranial Magnetic Stimulation for Speech Cortical Mapping

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 ...

Utilizing Repetitive Transcranial Magnetic Stimulation to Improve Language Function in Stroke Patients with Chronic Non-fluent Aphasia

Transcranial magnetic stimulation (TMS) has been shown to significantly improve language function in patients with non-fluent aphasia1. In this experiment, we demonstrate the administration of low-frequency repetitive TMS (rTMS) to an optimal stimulation site in the right hemisphere in patients with chronic non-fluent aphasia. A battery of standardized language measures is administered in order to assess baseline performance. Patients are subsequently randomized to either receive real rTMS or initial sham stimulation. Patients in the real stimulation undergo a site-finding phase, comprised of a series of six rTMS sessions administered over five days; stimulation is delivered to a different site in the right frontal lobe during each of these sessions. Each site-finding session consists of 600 pulses of 1 Hz rTMS, preceded and followed by a picture-naming task. By comparing the degree of transient change in naming ability elicited by stimulation of candidate sites, we are able to locate the area of optimal response for each individual patient. We then administer rTMS to this site during the treatment phase. During treatment, patients undergo a total of ten days of stimulation over the span of two weeks; each session is comprised of 20 min of 1 Hz rTMS delivered at 90% resting motor threshold. Stimulation is paired with an fMRI-naming task on the first and last days of treatment. After the treatment phase is complete, the language battery obtained at baseline is repeated two and six months following stimulation in order to identify rTMS-induced changes in performance. The fMRI-naming task is also repeated two and six months following treatment. Patients who are randomized to the sham arm of the study undergo sham site-finding, sham treatment, fMRI-naming studies, and repeat language testing two months after completing sham treatment. Sham patients then cross over into the real stimulation arm, completing real site-finding, real treatment, fMRI, and two- and six-month post-stimulation language testing.

We explore the use of repetitive transcranial magnetic stimulation (rTMS) to improve language abilities in patients with chronic stroke and non-fluent aphasia. After identifying a site in the right frontal gyrus for each patient that responds optimally to stimulation, we target this site during ten days of rTMS treatment.

Transcranial magnetic stimulation (TMS) has been shown to significantly improve language function in patients with non-fluent aphasia1. In this ...

Controlled Cortical Impact Model for Traumatic Brain Injury

Every year over a million Americans suffer a traumatic brain injury (TBI). Combined with the incidence of TBIs worldwide, the physical, emotional, social, and economical effects are staggering. Therefore, further research into the effects of TBI and effective treatments is necessary. The controlled cortical impact (CCI) model induces traumatic brain injuries ranging from mild to severe. This method uses a rigid impactor to deliver mechanical energy to an intact dura exposed following a craniectomy. Impact is made under precise parameters at a set velocity to achieve a pre-determined deformation depth. Although other TBI models, such as weight drop and fluid percussion, exist, CCI is more accurate, easier to control, and most importantly, produces traumatic brain injuries similar to those seen in humans. However, no TBI model is currently able to reproduce pathological changes identical to those seen in human patients. The CCI model allows investigation into the short-term and long-term effects of TBI, such as neuronal death, memory deficits, and cerebral edema, as well as potential therapeutic treatments for TBI.

Traumatic brain injuries (TBIs) remain a serious health problem. Using the controlled cortical impact surgery model, research on the effects of TBI and possible treatment methods may be performed.

Every year over a million Americans suffer a traumatic brain injury (TBI).  Combined with the incidence of TBIs worldwide, the physical, emotional, ...

Performing Permanent Distal Middle Cerebral with Common Carotid Artery Occlusion in Aged Rats to Study Cortical Ischemia with Sustained Disability

Stroke typically occurs in elderly people with a range of comorbidities including carotid (or other arterial) atherosclerosis, high blood pressure, obesity and diabetes. Accordingly, when evaluating therapies for stroke in animals, it is important to select a model with excellent face validity. Ischemic stroke accounts for 80% of all strokes, and the majority of these occur in the territory of the middle cerebral artery (MCA), often inducing infarcts that affect the sensorimotor cortex, causing persistent plegia or paresis on the contralateral side of the body. We demonstrate in this video a method for producing ischemic stroke in elderly rats, which causes sustained sensorimotor disability and substantial cortical infarcts. Specifically, we induce permanent distal middle cerebral artery occlusion (MCAO) in elderly female rats by using diathermy forceps to occlude a short segment of this artery. The carotid artery on the ipsilateral side to the lesion was then permanently occluded and the contralateral carotid artery was transiently occluded for 60 min. We measure the infarct size using structural T2-weighted magnetic resonance imaging (MRI) at 24 hr and 8 weeks after stroke. In this study, the mean infarct volume was 4.5% &#177; 2.0% (standard deviation) of the ipsilateral hemisphere at 24 hr (corrected for brain swelling using Gerriet&#8217;s equation, n = 5). This model is feasible and clinically relevant as it permits the induction of sustained sensorimotor deficits, which is important for the elucidation of pathophysiological mechanisms and novel treatments.

Here we present a protocol to produce permanent distal middle cerebral artery occlusion in elderly female rats with simultaneous occlusion of the carotid arteries to generate large cortical infarcts and sustained deficits. We show confirmation of the lesion size using structural MRI at 24 hr and 8 weeks after stroke.

Stroke typically occurs in elderly people with a range of comorbidities including carotid (or other arterial) atherosclerosis, high blood pressure, ...

A Protocol for the Use of Remotely-Supervised Transcranial Direct Current Stimulation (tDCS) in Multiple Sclerosis (MS)

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that uses low amplitude direct currents to alter cortical excitability. With well-established safety and tolerability, tDCS has been found to have the potential to ameliorate symptoms such as depression and pain in a range of conditions as well as to enhance outcomes of cognitive and physical training. However, effects are cumulative, requiring treatments that can span weeks or months and frequent, repeated visits to the clinic. The cost in terms of time and travel is often prohibitive for many participants, and ultimately limits real-world access. 
Following guidelines for remote tDCS application, we propose a protocol that would allow remote (in-home) participation that uses specially-designed devices for supervised use with materials modified for patient use, and real-time monitoring through a telemedicine video conferencing platform. We have developed structured training procedures and clear, detailed instructional materials to allow for self- or proxy-administration while supervised remotely in real-time. The protocol is designed to have a series of checkpoints, addressing attendance and tolerability of the session, to be met in order to continue to the next step. The feasibility of this protocol was then piloted for clinical use in an open label study of remotely-supervised tDCS in multiple sclerosis (MS). This protocol can be widely used for clinical study of tDCS.

A Protocol for the Use of Remotely-Supervised Transcranial Direct Current Stimulation tDCS in Multiple Sclerosis MS

The goal of this pilot study is to describe a protocol for the remotely-supervised delivery of transcranial direct current stimulation (tDCS) so that the procedure maintains standards of in-clinic practice, including safety, reproducibility, and tolerability. The feasibility of this protocol was tested in participants with multiple sclerosis (MS).

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that uses low amplitude direct currents to alter cortical ...

A Repetitive Concussive Head Injury Model in Mice

Despite the concussion/ mild traumatic brain injury (mTBI) being the most frequent occurrence of traumatic brain injury, there is still a lack of knowledge on the injury and its effects. To develop a better understanding of concussions, animals are often used because they provide a controlled, rigorous, and efficient model. Studies have adapted traditional animal models to perform mTBI to stimulate mild injury severity by changing the injury parameters. These models have been used because they can produce morphologically similar brain injuries to the clinical condition and provide a spectrum of injury severities. However, they are limited in their ability to present the identical features of injuries in patients. Using a traditional impact system, a repetitive concussive injury (rCHI) model can induce mild to moderate human-like concussion. The injury degree can be determined by measuring the period of loss of consciousness (LOC) with a sign of a transient termination of breathing. The rCHI model is beneficial to use for its accuracy and simplicity in determining mTBI effects and potential treatments.

Concussion presents the most common type of traumatic brain injury. Therefore, a repetitive concussive animal model, which replicates the important features of an injury in patients, may provide a means to study concussion in a rigorous, controlled, and efficient manner.

Despite the concussion/ mild traumatic brain injury (mTBI) being the most frequent occurrence of traumatic brain injury, there is still a lack of ...

A Mouse Model of Single and Repetitive Mild Traumatic Brain Injury

Mild Traumatic Brain Injury (mTBI) can result in the acute loss of brain function, including a period of confusion, a loss of consciousness (LOC), focal neurological deficits and even amnesia. Athletes participating in contact sports are at high risk of exposure to large number of mTBIs. In terms of the level of injury in a sporting athlete, a mTBI is defined as a mild injury that does not cause gross pathological changes, but does cause short-term neurological deficits that are spontaneously resolved. Despite previous attempts to model mTBI in mice and rats, many have reported gross adverse effects including skull fractures, intracerebral bleeding, axonal injury and neuronal cell death. Herein, we describe our highly reproducible animal model of mTBI that reproduces clinically relevant symptoms. This model uses a custom made pneumatic impactor device to deliver a closed-head trauma. This impact is made under precise velocity and deformation parameters, creating a reliable and reproducible model to examine the mechanisms that contribute to effects of single or repetitive concussive mTBI.

Athletes absorb several hundred mild traumatic brain injuries (mTBI)/concussions every year; however, the consequence of these on the brain is poorly understood. Therefore, an animal model of single and repetitive mTBI that consistently replicates clinically relevant symptoms provides the means to advance the study of mTBI and concussion.

Mild Traumatic Brain Injury (mTBI) can result in the acute loss of brain function, including a period of confusion, a loss of consciousness (LOC), focal ...

Updated Technique for Reliable, Easy, and Tolerated Transcranial Electrical Stimulation Including Transcranial Direct Current Stimulation

Transcranial direct current stimulation (tDCS) is a noninvasive method of neuromodulation using low-intensity direct electrical currents. This method of brain stimulation presents several potential advantages compared to other techniques, as it is noninvasive, cost-effective, broadly deployable, and well-tolerated provided proper equipment and protocols are administered. Even though tDCS is apparently simple to perform, correct administration of the tDCS session, especially the electrode positioning and preparation, is vital for ensuring reproducibility and tolerability. The electrode positioning and preparation steps are traditionally also the most time consuming and error-prone. To address these challenges, modern tDCS techniques, using fixed-position headgear and pre-assembled sponge electrodes, reduce complexity and setup time while also ensuring that the electrodes are consistently placed as intended. These modern tDCS methods present advantages for research, clinic, and remote-supervised (at home) settings. This article provides a comprehensive step-by-step guide for administering a tDCS session using fixed-position headgear and pre-assembled sponge electrodes. This guide demonstrates tDCS using commonly applied montages intended for motor cortex and dorsolateral prefrontal cortex (DLPFC) stimulation. As described, selection of the head size and montage-specific headgear automates electrode positioning. Fully assembled pre-saturated snap-electrodes are simply affixed to the set position snap-connectors on the headgear. The modern tDCS method is shown to reduce setup time and reduce errors for both novice and expert operators. The methods outlined in this article can be adapted to different applications of tDCS as well as other forms of transcranial electrical stimulation (tES) such as transcranial alternating current stimulation (tACS) and transcranial random noise stimulation (tRNS). However, since tES is application specific, as appropriate, any methods recipe is customized to accommodate subject, indication, environment, and outcome specific features.

When administering transcranial direct current stimulation (tDCS), reproducible electrode preparation and placement are vital for a tolerated and effective session. The purpose of this article is to demonstrate updated modern setup procedures for the administration of tDCS and related transcranial electrical stimulation techniques, such as transcranial alternating current stimulation (tACS).

Transcranial direct current stimulation (tDCS) is a noninvasive method of neuromodulation using low-intensity direct electrical currents. This method of ...

Virtual Reality Tools for Assessing Unilateral Spatial Neglect: A Novel Opportunity for Data Collection

Unilateral spatial neglect (USN) is a syndrome characterized by inattention to or inaction in one side of space and affects between 23-46% of acute stroke survivors. The diagnosis and characterization of these symptoms in individual patients can be challenging and often requires skilled clinical staff. Virtual reality (VR) presents an opportunity to develop novel assessment tools for patients with USN.
We aimed to design and build a VR tool to detect and characterize subtle USN symptoms, and to test the tool on subjects treated with inhibitory repetitive transcranial magnetic stimulation (TMS) of cortical regions associated with USN.
We created three experimental conditions by applying TMS to two distinct regions of cortex associated with visuospatial processing- the superior temporal gyrus (STG) and the supramarginal gyrus (SMG) - and applied sham TMS as a control. We then placed subjects in a virtual reality environment in which they were asked to identify the flowers with lateral asymmetries of flowers distributed across bushes in both hemispaces, with dynamic difficulty adjustment based on each subject's performance. 
We found significant differences in average head yaw between subjects stimulated at the STG and those stimulated at the SMG and marginally significant effects in the average visual axis.
VR technology is becoming more accessible, affordable, and robust, presenting an exciting opportunity to create useful and novel game-like tools. In conjunction with TMS, these tools could be used to study specific, isolated, artificial neurological deficits in healthy subjects, informing the creation of VR-based diagnostic tools for patients with deficits due to acquired brain injury. This study is the first to our knowledge in which artificially generated USN symptoms have been evaluated with a VR task.

The goal was to design, build, and pilot a novel virtual reality task to detect and characterize unilateral spatial neglect, a syndrome affecting 23-46% of acute stroke survivors, expanding the role of virtual reality in the study and management of neurologic disease.

Unilateral spatial neglect (USN) is a syndrome characterized by inattention to or inaction in one side of space and affects between 23-46% of acute stroke ...

Repetitive Blood Sampling from the Subclavian Vein of Conscious Rat

Rats are widely used in pharmacokinetics (PK) and toxicokinetic (TK) studies that need to collect a certain amount of blood at specific time points to detect drug exposure. The rat blood sampling method determines the quality of the plasma and further affects the precision of the test results. The subclavian vein blood collection method described in this protocol collects blood samples repeatedly in the conscious state of animals to meet the needs of PK and TK tests. The skills of restraint handling and appropriate procedure of needle incision ensure the success rate of blood collection. It is easy to operate while ensuring the quality of plasma and at the same time catering to animal welfare. However, this method requires skilled operation, and an improper one may cause animal weakness, pain, lameness, and even mortality. The current method has been used in the testing facility for a 4-week oral toxicity study in Sprague Dawley (SD) rats with TK. The maximum amount of blood collected within 24 h did not exceed 20% of the animal's total blood. The animals' body weight was more than 200 g for males and females. The data showed that the animals' bodyweight increased steadily every week, and the clinical observation was normal after repetitive sample collection.

The present protocol describes a simple and efficient method for collecting blood from the subclavian vein in rats. It enables rapid, timely, and easily identifiable sampling without anesthesia and obtains high-quality blood through repetitive sample collection.

Rats are widely used in pharmacokinetics (PK) and toxicokinetic (TK) studies that need to collect a certain amount of blood at specific time points to ...