1. Preparação <ol class="lalpha"><li> Para começar, obtenha uma varredura de linha de base anatômica de seu assunto. Isto deve ser feito alguns dias antes do experimento real. </li><li> Em seguida, coloque o scan em seu pacote sem moldura estereotáxica software. </li><li> Por fim, localize e alvo as suas coordenadas de estímulo. Neste caso, estaremos visando o lóbulo parietal inferior esquerdo. </li></ol> 2. A verificação inicial <ol class="lalpha"><li> No dia do experimento, o assunto será, mais uma vez, começar no aparelho de ressonância magnética. </li><li> Comece com uma varredura anatômica. </li><li> Em seguida, realizar três corridas experimentação funcional. Para este experimento, a tarefa é bastante simples: um ponto de fixação é apresentado no campo central do sujeito de visão, e ele / ela é simplesmente ficar olhando passivamente. </li></ol> 3. Preparação TMS <ol class="lalpha"><li> Porque os efeitos da EMTr são transitórios, o tempo é da essência quando se combina TMS e fMRI. É imperativo que você começa a voltar assunto no scanner o mais rapidamente possível após a interrupção da estimulação. Devido a isso, você vai querer usar um dispositivo portátil TMS estacionados em uma sala adjacente ou o mais próximo possível da digitalização bay-possível. Neste caso, estamos usando uma porta de set-up em uma suíte de observação portátil ao lado do scanner. </li><li> Carga inicial de seu objeto pré-alvo de ressonância magnética para o pacote de software estereotáxica. </li><li> Finalmente, link e calibrar sua bobina estimulante com o equipamento de estereotaxia - neste caso, vamos alinhar um conjunto de sensores de infravermelho para registrar centralidade da bobina. </li></ol> 4. Determinar parâmetros TMS <ol class="lalpha"><li> Quando o assunto chega, sente-se ele / ela confortavelmente em uma cadeira. </li><li> Em seguida, calibre da cabeça da pessoa com o equipamento sterotaxy. Neste caso, vamos usar sensores de infravermelho para registrar âncoras posicionamento várias: ambas as orelhas, o nariz, eo násio. </li><li> Determinar o limiar de seu objeto do motor em repouso. </li><li> Se queremos excitar o córtex do sujeito, vamos configurar a máquina TMS a 20 Hz, com uma potência de estímulo limiar motor 110%. Se queremos inibir córtex do sujeito, vamos configurar a máquina TMS a 1 Hz a 110% do limiar motor. Embora você vai querer explorar ambos os parâmetros durante todo o curso de um estudo completo, vamos apenas olhar para uma cadeia de 20 Hz rTMS excitatórios neste artigo. </li><li> Finalmente, estabelecer um padrão de estimulação dos dois trens em segundo lugar com 28 períodos de descanso segundo. </li></ol> 5. Estimulação TMS <ol class="lalpha"><li> Anterior à estimulação, prepare o assunto para ir diretamente no TMS seguintes scanner. Isto inclui a remoção de metal e garantindo o sujeito tem usado o banheiro. </li><li> Segurando a bobina tangencial para o couro cabeludo, use seu equipamento de estereotaxia para localizar e alvo do site do sujeito estimulação. </li><li> Ligue a máquina do sistema de refrigeração da bobina. </li><li> Começar a estimulação! Para este protocolo, vamos realizar 45 trens estímulo total. Menos 2 segundos de um trem com 28 breaks segundo, teremos um tempo stim total de 23 minutos. </li></ol> 6. Voltar para o Scanner <ol class="lalpha"><li> Uma vez que a estimulação é completo, é importante para obter o assunto de volta ao scanner o mais rápido possível. Para fazer essa transição tão simples quanto possível, garantir que o seu scanner é preparado e pronto para ir. Nosso conselho é para elevar a plataforma, corpo e reduzir o número ea duração das verificações localizer a um mínimo. </li></ol> 7. Finais de digitalização <ol class="lalpha"><li> Porque os efeitos da EMTr são transitórios, a sessão de digitalização final deve começar com as corridas funcional. Mais uma vez, vamos realizar três, seis minutos-runs de fixação passiva. </li><li> Após a execução experimental estão completos, terminar com uma varredura anatômica. </li></ol> 8. Resultados representante <img src="/files/ftp_upload/2271/2271fig1.jpg" alt="Figura 1" /> Figura 1. Os dados sugerem que 20 Hz rTMS estímulo ao lóbulo parietal inferior esquerdo, apesar de facilitar a excitabilidade local, atua para diminuir a conectividade funcional dentro da rede padrão.

<ol>
	<li>Raichle, M. E., MacLeod, A. M., Snyder, A. Z., Powers, W. J., Gusnard, D. A., Shulman, G. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+default+mode+of+brain+function.">A default mode of brain function.</a> Proc. Nat. Acad. Sciences. 98 (2), 676-682 (2001).</li><li>Buckner, R. L., Andrews-Hanna, J. R., Schacter, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+brain's+default+network:+anatomy,+function+and+relevance+to+disease.">The brain's default network: anatomy, function and relevance to disease.</a> Ann. N.Y. Acad. Sci. 1124, 1-38 (2008).</li><li>Raichle, M. E., Snyder, A. Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+default+mode+of+brain+function:+a+brief+history+of+an+evolving+idea.">A default mode of brain function: a brief history of an evolving idea.</a> Neuroimage. 37 (4), 1083-1090 (2007).</li><li>Whitfield-Gabrieli, S., Thermenos, H. W., Milanovic, S., Tsuang, M. T., Faraone, S. V., McCarley, R. W., Shenton, M. E., Green, A. I., Nieto-Castanon, A., LaViolette, P., Wojcik, J., Gabrieli, J. D., Sidman, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyperactivity+and+hyperconnectivity+of+the+default+network+in+schizophrenia+and+in+first-degreerelatives+of+persons+with+schizophrenia.">Hyperactivity and hyperconnectivity of the default network in schizophrenia and in first-degreerelatives of persons with schizophrenia.</a> Proc. Nat. Acad. Sciences. 106 (4), 1279-1284 (2009).</li><li>Pomarol-Clotet, E., Salvardor, R., Sarro, S., Gomar, J., Vila, F., Martinez, A., Guerrrero, A., Ortiz-Gil, J., Sans-Sansa, B., Capdevila, A., Cebamanos, J. M., McKenna, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Failure+to+deactivate+the+prefrontal+cortex+in+schizophrenia:+dysfunction+of+the+default+mode+network?.">Failure to deactivate the prefrontal cortex in schizophrenia: dysfunction of the default mode network?.</a> Psychol Med. 38 (8), 1185-1193 (2008).</li><li>Garrity, A. G., Pearlson, G. D., McKiernan, K., Lloyd, D., Kiehl, K. A., Calhoun, V. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aberrant+"default+mode"+functional+connectivity+in+schizophrenia.">Aberrant "default mode" functional connectivity in schizophrenia.</a> American Journal of Psychiatry. 164, 450-457 (2007).</li><li>Kennedy, D. P., Redcay, E., Courchesne, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Failing+to+deactivate:+Resting+functional+abnormalities+in+autism.">Failing to deactivate: Resting functional abnormalities in autism.</a> Proc. Nat. Acad. Sciences. 103 (21), 8275-8280 (2007).</li><li>c Buckner, R. L., Snyder, A. Z., Shannon, B. J., LaRossa, G., Sachs, R., Fotenos, A. F., Sheline, Y. I., Klunk, W. E., Mathis, C. A., Morris, J. C., Mintun, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular,+structural,+and+functional+characterizations+of+Alzheimer's+disease:+evidence+for+a+relationship+between+default+activity,+amyloid,+and+memory.">Molecular, structural, and functional characterizations of Alzheimer's disease: evidence for a relationship between default activity, amyloid, and memory.</a> Journal of Neuroscience. 34, 7709-7717 (2005).</li><li>Pascual-Leone, A., Davey, M., Wassermann, E. M., Rothwell, J., Puri, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Handbook of Transcranial Magnetic Stimulation. , (2002).</li></ol>

Não há conflitos de interesse declarados.

<p class="jove_content"&gt; Ao se realizar um TMS offline / experiência de ressonância magnética, sem dúvida o aspecto mais importante envolve a transição rápida e sem esforço a partir do local de estimulação para a baía de ressonância magnética. Como tal, valeria a pena revisitar várias das idéias sugeridas acima para ajudar nessa transição. Primeiro: use uma máquina portátil TMS criado em um local tão perto da baía de ressonância magnética quanto possível. Dois: contornar qualquer mecanismo automático stand-by ou equi...

<ul><li> MRI Equipado para fMRI (na foto em vídeo é uma Philips) </li><li> TMS dispositivo capaz de estimulação repetitiva (retratado no vídeo é um Magstim) </li><li> Equipamentos Estereotaxia Frameless (foto no vídeo é Brainsight) </li><li> Tampões para os ouvidos </li><li> Cadeira para Assunto durante a estimulação </li><li> Tela de projeção traseira ou ressonância magnética Goggles Compatível </li><li> Tela em branco Estímulos </li></ul>

combining transcranial magnetic stimulation and fmri to examine the default mode network

A rede de modo padrão é um grupo de regiões do cérebro que estão ativas quando uma pessoa não está focada no mundo exterior eo cérebro está em &quot;descanso vigília.&quot; 1,2,3 Acredita-se que a rede de modo padrão corresponde a auto-referencial ou &quot;implementação interna&quot; 2,3. Postula-se que, em humanos, a atividade dentro da rede de modo padrão é correlacionada com certas patologias (por exemplo, hiper-ativação tem sido associada à esquizofrenia 4,5,6 e transtornos do espectro autista, enquanto 7 hipo-ativação da rede tem sido associada a doença de Alzheimer e outras doenças neurodegenerativas 8). Como tal modulação, não invasivo desta rede pode representar uma intervenção potencial terapêutico para uma série de patologias neurológicas e psiquiátricas relacionadas com a ativação da rede anormal. Uma ferramenta possível efeito dessa modulação é Estimulação Magnética Transcraniana: uma neurostimulatory não-invasivo e técnica neuromoduladores que pode transitoriamente ou duradoura modular a excitabilidade cortical (aumentando ou diminuindo-a), através da aplicação de pulsos de campo magnético localizada 9. A fim de explorar a propensão a rede de modo padrão em relação à tolerância e de modulação, estaremos combinando TMS (no lobo parietal esquerdo inferior) com ressonância magnética funcional (fMRI). Através deste artigo, vamos examinar o protocolo e as considerações necessárias de forma a combinar essas duas ferramentas da neurociência.

Watch this Scientific Journal Video about Combining Transcranial Magnetic Stimulation and fMRI to Examine the Default Mode Network at JoVE.com

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

Neste artigo, vamos examinar a metodologia e considerações relevantes para a combinação de TMS e fMRI para examinar os efeitos de estimulação cerebral na rede padrão.

Combinando Estimulação Magnética Transcraniana e fMRI para o Exame da rede de modo padrão

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 ...

combining-transcranial-magnetic-stimulation-fmri-to-examine-default

Universidad de Cartagena UDEC

Research

JoVE Journal

Neuroscience

12.8K visualizações.  Beth Israel Deaconess Medical Center. Neste artigo, vamos examinar a metodologia e considerações relevantes para a combinação de TMS e fMRI para examinar os efeitos de estimulação cerebral na rede padrão.

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

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.

Transcraniana direto Estimulação atual e simultânea Ressonância Magnética Funcional

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

Comportamento

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.

Estimulação Magnética Transcraniana para investigar relações causais Brain-comportamentais e seu Curso de Tempo

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

Simultaneous Transcranial Alternating Current Stimulation and Functional Magnetic Resonance Imaging

Transcranial alternating current stimulation (tACS) is a promising tool for noninvasive investigation of brain oscillations. TACS employs frequency-specific stimulation of the human brain through current applied to the scalp with surface electrodes. Most current knowledge of the technique is based on behavioral studies; thus, combining the method with brain imaging holds potential to better understand the mechanisms of tACS. Because of electrical and susceptibility artifacts, combining tACS with brain imaging can be challenging, however, one brain imaging technique that is well suited to be applied simultaneously with tACS is functional magnetic resonance imaging (fMRI). In our lab, we have successfully combined tACS with simultaneous fMRI measurements to show that tACS effects are state, current, and frequency dependent, and that modulation of brain activity is not limited to the area directly below the electrodes. This article describes a safe and reliable setup for applying tACS simultaneously with visual task fMRI studies, which can lend to understanding oscillatory brain function as well as the effects of tACS on the brain.

Transcranial alternating current stimulation (tACS) is a promising tool for noninvasive investigation of brain oscillations, though its effects are not completely understood. This article describes a safe and reliable setup for applying tACS simultaneously with functional magnetic resonance imaging, which can increase understanding oscillatory brain function and effects of tACS.

Estimulação de corrente alternada transcraniana simultânea e ressonância magnética funcional

Transcranial alternating current stimulation (tACS) is a promising tool for noninvasive investigation of brain oscillations. TACS employs ...

Network Analysis of the Default Mode Network Using Functional Connectivity MRI in Temporal Lobe Epilepsy

Functional connectivity MRI (fcMRI) is an fMRI method that examines the connectivity of different brain areas based on the correlation of BOLD signal fluctuations over time. Temporal Lobe Epilepsy (TLE) is the most common type of adult epilepsy and involves multiple brain networks. The default mode network (DMN) is involved in conscious, resting state cognition and is thought to be affected in TLE where seizures cause impairment of consciousness. The DMN in epilepsy was examined using seed based fcMRI. The anterior and posterior hubs of the DMN were used as seeds in this analysis. The results show a disconnection between the anterior and posterior hubs of the DMN in TLE during the basal state. In addition, increased DMN connectivity to other brain regions in left TLE along with decreased connectivity in right TLE is revealed. The analysis demonstrates how seed-based fcMRI can be used to probe cerebral networks in brain disorders such as TLE.

The Default Mode Network (DMN) in Temporal Lobe Epilepsy (TLE) is analyzed in the resting state of the brain using seed-based functional connectivity MRI (fcMRI).

Análise de Redes da rede de modo padrão Usando Funcional Conectividade RM em Epilepsia do Lobo Temporal

Functional connectivity MRI (fcMRI) is an fMRI method that examines the connectivity of different brain areas based on the correlation of BOLD signal ...

Medicina

Extracting Visual Evoked Potentials from EEG Data Recorded During fMRI-guided Transcranial Magnetic Stimulation

Transcranial Magnetic Stimulation (TMS) is an effective method for establishing a causal link between a cortical area and cognitive/neurophysiological effects. Specifically, by creating a transient interference with the normal activity of a target region and measuring changes in an electrophysiological signal, we can establish a causal link between the stimulated brain area or network and the electrophysiological signal that we record. If target brain areas are functionally defined with prior fMRI scan, TMS could be used to link the fMRI activations with evoked potentials recorded. However, conducting such experiments presents significant technical challenges given the high amplitude artifacts introduced into the EEG signal by the magnetic pulse, and the difficulty to successfully target areas that were functionally defined by fMRI. Here we describe a methodology for combining these three common tools: TMS, EEG, and fMRI. We explain how to guide the stimulator&#39;s coil to the desired target area using anatomical or functional MRI data, how to record EEG during concurrent TMS, how to design an ERP study suitable for EEG-TMS combination and how to extract reliable ERP from the recorded data. We will provide representative results from a previously published study, in which fMRI-guided TMS was used concurrently with EEG to show that the face-selective N1 and the body-selective N1 component of the ERP are associated with distinct neural networks in extrastriate cortex. This method allows us to combine the high spatial resolution of fMRI with the high temporal resolution of TMS and EEG and therefore obtain a comprehensive understanding of the neural basis of various cognitive processes.

This paper describes a method for collecting and analyzing electroencephalography (EEG) data during concurrent transcranial magnetic stimulation (TMS) guided by activations revealed with functional magnetic resonance imaging (fMRI). A method for TMS artifact removal and extraction of event related potentials is described as well as considerations in paradigm design and experimental setup.

Extraindo potenciais evocados visuais de dados EEG gravado durante fMRI-guiada Estimulação Magnética Transcraniana

Transcranial Magnetic Stimulation (TMS) is an effective method for establishing a causal link between a cortical area and cognitive/neurophysiological ...

Neurociência

Developing Neuroimaging Phenotypes of the Default Mode Network in PTSD: Integrating the Resting State, Working Memory, and Structural Connectivity

Complementary structural and functional neuroimaging techniques used to examine the Default Mode Network (DMN) could potentially improve assessments of psychiatric illness severity and provide added validity to the clinical diagnostic process. Recent neuroimaging research suggests that DMN processes may be disrupted in a number of stress-related psychiatric illnesses, such as posttraumatic stress disorder (PTSD).
Although specific DMN functions remain under investigation, it is generally thought to be involved in introspection and self-processing. In healthy individuals it exhibits greatest activity during periods of rest, with less activity, observed as deactivation, during cognitive tasks, e.g., working memory. This network consists of the medial prefrontal cortex, posterior cingulate cortex/precuneus, lateral parietal cortices and medial temporal regions.
Multiple functional and structural imaging approaches have been developed to study the DMN. These have unprecedented potential to further the understanding of the function and dysfunction of this network. Functional approaches, such as the evaluation of resting state connectivity and task-induced deactivation, have excellent potential to identify targeted neurocognitive and neuroaffective (functional) diagnostic markers and may indicate illness severity and prognosis with increased accuracy or specificity. Structural approaches, such as evaluation of morphometry and connectivity, may provide unique markers of etiology and long-term outcomes. Combined, functional and structural methods provide strong multimodal, complementary and synergistic approaches to develop valid DMN-based imaging phenotypes in stress-related psychiatric conditions. This protocol aims to integrate these methods to investigate DMN structure and function in PTSD, relating findings to illness severity and relevant clinical factors.

This protocol describes the complementary neuroimaging techniques of resting state structural connectivity, task-induced deactivation, and structural connectivity analyses to examine the default network in post-traumatic stress disorder. The use of synergistic methods could potentially lead to improved diagnostics and assessments of severity, outcome, and other relevant clinical factors.

Desenvolver Neuroimagem fenótipos da rede de modo padrão no TEPT: Integrando o estado de repouso, Memória de Trabalho e Conectividade Estrutural

Complementary structural and functional neuroimaging techniques used to examine the Default Mode Network (DMN) could potentially improve assessments 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.

Efeitos da estimulação da corrente alternada transcraniana no córtex Motor primário por on-line abordagem combinada com estimulação magnética transcraniana

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

Mapping the After-effects of Theta Burst Stimulation on the Human Auditory Cortex with Functional Imaging

Auditory cortex pertains to the processing of sound, which is at the basis of speech or music-related processing1. However, despite considerable recent progress, the functional properties and lateralization of the human auditory cortex are far from being fully understood. Transcranial Magnetic Stimulation (TMS) is a non-invasive technique that can transiently or lastingly modulate cortical excitability via the application of localized magnetic field pulses, and represents a unique method of exploring plasticity and connectivity. It has only recently begun to be applied to understand auditory cortical function 2. 
An important issue in using TMS is that the physiological consequences of the stimulation are difficult to establish. Although many TMS studies make the implicit assumption that the area targeted by the coil is the area affected, this need not be the case, particularly for complex cognitive functions which depend on interactions across many brain regions 3. One solution to this problem is to combine TMS with functional Magnetic resonance imaging (fMRI). The idea here is that fMRI will provide an index of changes in brain activity associated with TMS. Thus, fMRI would give an independent means of assessing which areas are affected by TMS and how they are modulated 4. In addition, fMRI allows the assessment of functional connectivity, which represents a measure of the temporal coupling between distant regions. It can thus be useful not only to measure the net activity modulation induced by TMS in given locations, but also the degree to which the network properties are affected by TMS, via any observed changes in functional connectivity.
Different approaches exist to combine TMS and functional imaging according to the temporal order of the methods. Functional MRI can be applied before, during, after, or both before and after TMS. Recently, some studies interleaved TMS and fMRI in order to provide online mapping of the functional changes induced by TMS 5-7. However, this online combination has many technical problems, including the static artifacts resulting from the presence of the TMS coil in the scanner room, or the effects of TMS pulses on the process of MR image formation. But more importantly, the loud acoustic noise induced by TMS (increased compared with standard use because of the resonance of the scanner bore) and the increased TMS coil vibrations (caused by the strong mechanical forces due to the static magnetic field of the MR scanner) constitute a crucial problem when studying auditory processing. 
This is one reason why fMRI was carried out before and after TMS in the present study. Similar approaches have been used to target the motor cortex 8,9, premotor cortex 10, primary somatosensory cortex 11,12 and language-related areas 13, but so far no combined TMS-fMRI study has investigated the auditory cortex. The purpose of this article is to provide details concerning the protocol and considerations necessary to successfully combine these two neuroscientific tools to investigate auditory processing. 
Previously we showed that repetitive TMS (rTMS) at high and low frequencies (resp. 10 Hz and 1 Hz) applied over the auditory cortex modulated response time (RT) in a melody discrimination task 2. We also showed that RT modulation was correlated with functional connectivity in the auditory network assessed using fMRI: the higher the functional connectivity between left and right auditory cortices during task performance, the higher the facilitatory effect (i.e. decreased RT) observed with rTMS. However those findings were mainly correlational, as fMRI was performed before rTMS. Here, fMRI was carried out before and immediately after TMS to provide direct measures of the functional organization of the auditory cortex, and more specifically of the plastic reorganization of the auditory neural network occurring after the neural intervention provided by TMS. 
Combined fMRI and TMS applied over the auditory cortex should enable a better understanding of brain mechanisms of auditory processing, providing physiological information about functional effects of TMS. This knowledge could be useful for many cognitive neuroscience applications, as well as for optimizing therapeutic applications of TMS, particularly in auditory-related disorders.

Auditory processing is the basis of speech and music-related processing. Transcranial Magnetic Stimulation (TMS) has been used successfully to study cognitive, sensory and motor systems but has rarely been applied to audition. Here we investigated TMS combined with functional Magnetic Resonance Imaging to understand the functional organization of auditory cortex.

Mapear as sequelas de Theta Explosão Estimulação no córtex auditivo humano com Imagem Funcional

Auditory cortex pertains to the processing of sound, which is at the basis of speech or music-related processing1. However, despite considerable recent ...

Biologia

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.

Estimulação magnética transcraniana combinada e Eletroencefalografia do córtex pré-frontal Dorsolateral

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

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.

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.

Medir e manipular vias neurais funcionalmente específicas no sistema motor humano com estimulação magnética transcraniana

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