Os autores gostariam de agradecer Matti S. Hämäläinen, Lilla Zöllei e três revisores anônimos por seus comentários úteis. Fontes de financiamento: R00DC010196 (AKCL); T32DC000018 (EDL); T32DC005361 (RKM).

1. Aquisição de Dados e Processamento anatômica <ol><li> Adquirir uma magnetização preparado rápida gradiente eco (MPRAGE) exame de ressonância magnética do assunto. Isto pode demorar de 5-10 min, dependendo de qual protocolo verificação específica for utilizado. </li><li> Adquirir mais dois tiro baixo ângulo rápido (FLASH) exames de ressonância magnética (ângulos de inclinação = 5 ° e 30 °) se os dados de EEG são usados ​​para análise de imagem inversa, como seqüências FLASH proporcionar contraste tecido diferente das seqüências MPRAGE padrão 1. </li><li> Use FreeSurfer software (ver tabela) 2, 3 reconstruir a superfície cortical e configurar M indivíduo / espaço de origem EEG dipolo. <ol><li> Este espaço de origem é restrito ao limite massa cinzenta / branco segmentada da verificação MPRAGE. Cada hemisfério contém cerca de 100.000 potenciais vértices, espaçadas de ~ 1 mm. Para a estimativa da amplitude dipolo (ver abaixo), utilizar um espaçamento da grelha, de 7 mm, o que produz ~ 3000 dipolos por hemisfério. </li></ol></li><li> Reconstruira pele do crânio, exterior e superfícies internas do crânio a partir das imagens e flash usando MPRAGE MNE (ver tabela) e FreeSurfer. Usar estas superfícies para gerar um modelo de três camadas de elementos de contorno (MEC). </li></ol> 2. M / EEG de Aquisição de Dados <ol><li> Prepare assunto para M / EEG gravação. <ol><li> Consulte a Liu et al 4 para detalhes de eletrooculograma e preparação do eletrodo de referência, bem como a digitalização dos marcos fiduciais do sujeito, bobinas cabeça-posição indicadoras (HPI) e eletrodos de EEG. </li></ol></li><li> Uma vez sujeito está sentado no MEG, medir a posição da cabeça usando as bobinas HPI. </li><li> Iniciar a gravação. Comece a apresentação de estímulos auditivos e visuais. <ol><li> Muitos hardware e soluções de software estão disponíveis para realizar a apresentação do estímulo (por exemplo., Apresentação, E-Prime). Nós usamos um Tucker-Davis Technologies RZ6 para a apresentação do estímulo auditivo eo gatilho estamparia, com Psychtoolbox 5 para visual stimulus apresentação, ambas controladas pelo MATLAB. Testando as latências auditivas e visuais, utilizando um microfone e fotodiodo acoplado à tela e, posteriormente, assegurando que não há jitter observável (que pode exigir a apresentação definindo projetor para sua resolução nativa) antes da experiência ajuda a garantir a integridade timing. </li></ol></li><li> Assunto responde a estímulos auditivos e visuais através de uma caixa de botões óptico durante a execução de tarefa comportamental. </li><li> Guardar todos os estímulos, parâmetros experimentais e arquivos de dados para análise off-line. </li></ol> 3. M / EEG co-registo com IRM Digitalização e Processamento de Dados <ol><li> Usando o software MNE, carregar dados digitalizadoras e modelo sujeito cabeça reconstruída ressonância magnética. Escolha marcos fiduciais para iniciar processo de co-registo e continuar a usar procedimento de alinhamento automático para completar transformação de coordenadas (Figura 2). </li><li> Para relacionar a localização de cada dipolo no sp fonteace com a localização de cada sensor, combinar os dados gravados HPI (ver 2.2) para calcular uma solução para a frente com o BEM três camadas (ver 1.4) </li><li> Inspecione todos gravados M / EEG dados e identificar canais que têm variância excepcionalmente alta ou são completamente plana. Definir esses canais como canais ruins. </li><li> Usar o sinal de projecção espaço-6 ou técnicas de redução de ruído diferentes (tais como a separação de sinal do espaço 7) projectar ou separar padrões de campo espaciais originado de contaminação ambiental ambiente campo ou de outros sinais fisiológicos indesejáveis, tais como aquelas associadas com olho-pisca e artefactos cardíacos (Figura 3). <ol><li> Aplicar no domínio do tempo de remoção artefato (por exemplo., Removendo epochs contendo sinais de amplitude anormalmente elevados, devido à cravação de um canal) e no domínio da frequência de remoção artefato (por exemplo., Banda de filtragem no entalhe 50 ou 60 Hz de frequência de linha) para aumentar ainda mais a sinal-para-ruído. </li></ol></li><li> Identificar um período de linha de base em que o sujeito não foi executar qualquer tarefa (por exemplo., 200 ms período antes do início de cada ensaio). Gerar uma média de linha de base dessas épocas, a fim de se obter uma estimativa do ruído (também conhecido como a matriz de covariâncias). </li><li> Identificar épocas de interesse (por exemplo, apenas coletando épocas corretas com respostas comportamentais.) E definir as condições para contrastes experimentais (por exemplo, épocas associado com o assunto de ter mudado a sua atenção auditiva para o hemicampo oposto como originalmente cued -. &quot;Switch&quot; condição - versus assunto manter a atenção no hemicampo original - &quot;Hold&quot; condição). Gerar uma resposta média para cada uma das condições definidas. <ol><li> Estas médias podem ser de base corrigida ou não dependendo dos parâmetros experimentais (v. 8), os dados aqui apresentados são de linha de base corrigida. </li></ol></li><li> Combinar a matriz de covariância (3.5) e da solução para a frente computadorizada (3,2) para se obter umdistribuídos operador inverso corticalmente constrangido mínimo norma, que relaciona as medições do sensor de dipolo estimativas atuais no espaço de origem. <ol><li> Você pode restringir ou cerca de fixar a orientação dipolo para a direção cortical normal 9. </li></ol></li><li> Gerar um &quot;filme cérebro&quot; da estimativa distribuída dipolo (ou seja., A estimativa actual de cada local de dipolo no espaço de origem no tempo) para cada condição experimental (Figura 4). <ol><li> Dependendo das características temporais de seu projeto experimental, você pode bin seus dados em tempo por uma média de estimativas atuais usando não sobrepostos janelas temporais. </li></ol></li></ol> 4. Inferência Estatística baseada em um sistema de coordenadas comum baseado na superfície <ol><li> Morph os &quot;filmes&quot; do cérebro de cada sujeito para um espaço (média) cortical comum com base em um sistema de coordenadas baseado na superfície que se alinha optimamente indivíduo sulcamento-gyral padrões 3. Isso nos permite comparar ou média atividade cortical em todas as disciplinas. (Figura 5). </li><li> Existem várias abordagens de inferência estatística. Vamos destacar três abordagens possíveis aqui. Abordagens que não são implementados no pacote de software pode ser escrito usando software-in personalizado nossos exemplos usamos o MATLAB para executar a não-paramétrico agrupamento espaço-temporal teste de permutação. Apesar da alta dimensionalidade (espaço x tempo x Assuntos) desses dados, todas estas abordagens podem ser realizados utilizando hardware padrão moderno de desktop em segundos (ROI; 4,3 abordagem) para horas (não-paramétrico de clusters; 4.5). </li><li> Região de interesse abordagem (ROI) <ol><li> Pode-se definir a ROI anatomicamente (por exemplo., Definido pelo algoritmo de divisão em parcelas automático 1) e / ou funcionalmente (por exemplo., Gravando uma tarefa funcional localizadora, como um passa / não passa tarefa saccade para identificar o oculomotoregiões R). </li><li> É possível restringir ainda mais a análise de um tempo específico, de interesse, que é apropriado para o seu paradigma experimental (p. ex., Um período de tempo imediatamente antes e após o início do estímulo de som). Você também pode usar a inferência estatística outro associado com análise de séries temporais. </li></ol></li><li> Todo o cérebro Bonferroni ou Falso-Discovery-Rate (FDR) correção <ol><li> Empregar a correção de Bonferroni ou FDR se você precisar de todo o cérebro, a análise de todos os tempos. </li><li> Gerar um mapa de estatística em cada local de dipolo e cada ponto do tempo usando estatísticas de teste apropriadas, como um teste t ou dentro de sujeitos-ANOVA para os dados de aproximadamente normalmente distribuídas. Por exemplo, z-score de mapeamento de parâmetros dinâmicos estatística das estimativas MNE para fixos fontes dipolo 10 pode ser usado quando emparelhado com uma correção para as correlações das estimativas (como a correção de Greenhouse Geisser-conservador). </li><li> Para Bonferronicorrecção, obter significativas de espaço-tempo por thresholding pontos a um nível de significância de 0,05, dividido pelo número de comparações (número de dipolos multiplicado pelo número de pontos de tempo). Para uma abordagem menos conservadora, use FDR correção p-valor 11. </li></ol></li><li> Não paramétrico de agrupamento espaço-temporal <ol><li> Utilize este método (com base em uma simples extensão de 12) para encontrar regiões de grande, ativação consistente espacial e temporal ao ser menos conservador do que a correção de Bonferroni, e menos propenso a erros de Tipo I estatísticos que o FDR, controlando para a taxa de erro família sábio . <ol><li> Porque esta abordagem utiliza permutação ou técnicas de Monte Carlo reamostragem, não se baseiam em pressupostos de normalidade dos dados, e só assume que as etiquetas são intercambiáveis ​​condição sob a hipótese nula. Embora seja mais intensivos computacionalmente do que as duas anteriores abordagens, pode ainda ser realizada em horas numaúnica máquina usando hardware moderno computador desktop. </li></ol></li><li> Gerar um mapa de estatística em cada local de dipolo e cada ponto de tempo utilizando a estatística de teste adequadas, como um t-teste. </li><li> Mapa limiar isto a um limiar de significado preliminar, por exemplo, p &lt;0,05. </li><li> Cluster estes pontos putativos significativas baseadas em espaço-temporal de proximidade, por exemplo. pontos importantes dentro de 5 ms e 5 mm de distância geodésica da outra são colocados no mesmo cluster. Marcar cada cluster resultante usando hipervolume ou significado total (por exemplo,. Soma de t-escores de pontos no cluster). </li><li> Realizar uma reamostragem padrão permutação (ou Monte Carlo reamostragem para maiores conjuntos de dados, por exemplo. Número de indivíduos N&gt; 10, para economizar em computação) teste com uma estatística máxima (ver exemplos 12 para teste de permutação). Resumidamente, para um subconjunto aleatório de indivíduos (escolher em qualquer lugar a partir de 0 a N indivíduos), as condições relabel being comparação antes de obter o mapa estatístico, realizar agrupamento no novo mapa estatístico, e obter a pontuação máxima para o grupo que nomes. Executar este procedimento em novas relabelings aleatórios para até 2 N permutações para obter uma distribuição da estatística máxima; realizando todas as 2 N relabelings possíveis produz o teste de permutação e utilizando um subconjunto aleatório de menos de 2 N relabelings produz um Monte Carlo (ou aleatória ) teste de permutação. </li><li> Obter o significado de um dado grupo original (a partir do rótulo original) através da determinação da proporção de tempo que os tamanhos máximos de fragmentação eram maiores do que o do conjunto original, por exemplo. aglomerados que eram maiores do que 95% dos aglomerados estatísticos máximas pode ser declarado significativo. <ol><li> Para uma discussão aprofundada sobre inferência estatística em MEG imagens fonte distribuído, consulte 13. </li></ol></li></ol></li><li> Os arquivos de dados resultantes pode ser vi<html> sualized de muitas maneiras, inclusive usando os formatos nativamente utilizados pelo software MNE para armazenar espaço-temporais estimativas corticais, ou seja, arquivos do STC. Estas, juntamente com as etiquetas que podem ser produzidos correspondentes às regiões significativas, podem ser gerados usando caixas de ferramentas MNE previstas MATLAB e Python. </li></ol> 5. Resultados representativos A Figura 6 mostra um conjunto de resultados representativos utilizando o paradigma comportamental descrito na Figura 4. Utilizando o procedimento de agrupamento não-paramétrico de espaço-temporal (4.5), a FEF direito é considerado significativo quando um sujeito está a executar uma tarefa reorientação em comparação com um padrão de tarefa (à esquerda Figura 6). Utilizando a abordagem de ROI (4.3), o curso de tempo da FEF direita é mostrado juntamente com o período de tempo em que estas duas condições são significativamente diferentes. p_upload/4262/4262fig1.jpg &quot;/&gt; Figura 1. Fluxo de trabalho para gerar um &quot;filme cérebro&quot; utilizando-corticalmente constrangido norma mínima estimativas-dipolo (cf., a Figura 1, em Liu et al., 2010). <img alt="Figura 2" src="/files/ftp_upload/4262/4262fig2.jpg" /> Figura 2. Software MNE utilizado para facilitar os canais de EEG e locais HPI co-registo para o espaço um sujeito coordenado ressonância magnética. <img alt="Figura 3" src="/files/ftp_upload/4262/4262fig3.jpg" /> Figura 3. Dados MEG antes e depois de usar SSP para remover cardíaca (destacado em laranja) e olho-pisca (destacado em azul-verde) artefatos e lowpass de filtragem para remover a linha-freqüência. <a href="http://www.jove.com/files/ftp_upload/4262/4262fig3large.jpg" target="_blank">Clique aqui para ver maior figura</a> . <pclass = &quot;jove_content&quot; fo: manter-together.within-page = &quot;always&quot;&gt; <img alt="Figura 4" src="/files/ftp_upload/4262/4262fig4.jpg" /> Figura 4 Um &quot;filme cérebro&quot; em espaço nativo sujeito cortical e o momento da apresentação audio-visual (com estímulos auditivos apresentados a 600 ms e um estímulo visual apresentado em -600 ms) num paradigma experimental (Nota:. Esta será apresentado como um filme no clipe de filme final) <img alt="Figura 5" src="/files/ftp_upload/4262/4262fig5.jpg" /> Figura 5. Comparação entre um ROI hipotética mapeado no espaço nativo de um sujeito cortical e depois se transformou em um espaço comum cortical. <img alt="Figura 6" src="/files/ftp_upload/4262/4262fig6.jpg" /> Figura 6. Representante agrupamento espaço-temporal e curso temporal associado com a condição experimental doisções testado.

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A fim de estimar a activação de dipolo no córtex do MEG / adquiridos dados de EEG, precisamos de resolver um problema inverso, que não tem uma solução única e estável a menos apropriados anatomicamente e fisiologicamente constrangimentos de som são aplicadas. Usando a restrição anatômica adquiridos para assuntos individuais usando ressonância magnética e adotar a norma-mínimo como critério de estimativa, podemos chegar a uma estimativa fonte inversa cortical atual que está de acordo com as medições do...

<table border="1"><tbody><tr><td> Nome de equipamentos / software </td><td> Empresa / fonte </td><td></td><td></td></tr><tr><td> 306-canal Vectorview MEG sistema </td><td> Eleka-Neuromag Ltd, </td><td></td><td></td></tr><tr><td> 1,5-T Avanto scanner de ressonância magnética </td><td> Siemens Medical Solutions </td><td></td><td></td></tr><tr><td> FreeSurfer </td><td></td><td></td><td> <a href="http://freesurfer.net/" target="_blank">http://freesurfer.net/</a> </td></tr><tr><td> MNE software </td><td></td><td></td><td> <a href="http://www.nmr.mgh.harvard.edu/martinos/userInfo/data/sofMNE.php" target="_blank">http://www.nmr.mgh.harvard.edu/martinos/userInfo/data/sofMNE.php</a> </td></tr><tr><td> Eletrodos de EEG </td><td> Produtos cérebro, EasyCap GmbH </td><td></td><td></td></tr><tr><td> 3Space Fastrak sistema </td><td> Polhemus </td><td></td><td></td></tr><tr><td> Caixa de botões óptico (FIU-932) </td><td> Projetos atuais </td><td></td><td></td></tr></tbody></table>

mapping cortical dynamics using simultaneous meg/eeg and anatomically-constrained minimum-norm estimates: an auditory attention example

Magneto e eletroencefalografia (MEG / EEG) são técnicas de neuroimagem que proporcionam uma alta resolução temporal particularmente adequado para investigar as redes corticais envolvidas no dinâmicos tarefas perceptivas e cognitivas, tais como atendimento a diferentes sons em um coquetel. Muitos estudos anteriores tenham utilizado os dados gravados no nível do sensor, isto é., Os campos magnéticos ou eléctricos dos potenciais registados fora e no couro cabeludo, e têm geralmente focada na actividade que é tempo de bloqueado para a apresentação do estímulo. Este tipo de evento relacionado campo / análise de potencial é particularmente útil quando há apenas um pequeno número de diferentes padrões dipolares que podem ser isolados e identificados no espaço e no tempo. Em alternativa, através da utilização de informação anatómica, estes padrões de campo diferentes podem ser localizados como fontes de corrente no córtex. No entanto, para uma resposta mais sustentada, que não pode ser bloqueado em tempo a um estímulo específico (p. ex.,, em preparação para a ouvir um dos dois simultaneamente apresentados dígitos faladas acordo com a função auditiva cued) ou pode ser distribuído através de múltiplas localizações espaciais desconhecidas a priori, o recrutamento de uma rede distribuída cortical podem não ser adequadamente capturado por meio de um número limitado de fontes focais. Aqui, nós descrevemos um processo que emprega anatómicas individuais dos dados de MRI para estabelecer uma relação entre as informações do sensor e a activação de dipolo no córtex através do uso da norma mínima estimativas (ENM). Esta abordagem de imagem inversa nos fornece uma ferramenta para análise da fonte distribuído. Para fins ilustrativos, vamos descrever todos os procedimentos que utilizam FreeSurfer MNE e software, tanto livremente disponíveis. Vamos resumir as seqüências de RM e etapas de análise necessários para produzir um modelo para a frente que nos permite relacionar o padrão de campo esperado causado pelos dipolos distribuídos no córtex sobre os sensores do M / EEG. Next, vamos percorrer os processos necessários que facilitem nos denoising os dados do sensor de contaminantes ambientais e fisiológicos. Iremos em seguida, descrevem o procedimento para a combinação de mapeamento e MEG / dados do sensor para o espaço de EEG cortical, produzindo desse modo uma família de séries de tempo da activação do dipolo cortical na superfície do cérebro (ou &quot;filmes cérebro&quot;) relacionadas com cada condição experimental. Finalmente, vamos destacar algumas técnicas estatísticas que nos permitem fazer inferência científica em uma população de assunto (ou seja., Realizar ao nível do grupo de análise) com base em um espaço de coordenadas comum cortical.

Watch this Scientific Journal Video about Mapping Cortical Dynamics Using Simultaneous MEG/EEG and Anatomically-constrained Minimum-norm Estimates: an Auditory Attention Example at JoVE.com

Mapping Cortical Dynamics Using Simultaneous MEG/EEG and Anatomically-constrained Minimum-norm Estimates: an Auditory Attention Example

Usamos magneto-e eletroencefalografia (MEG / EEG), combinado com informações anatômicas capturado por ressonância magnética (MRI), para mapear a dinâmica da rede cortical associado à atenção auditiva.

Mapeamento Dynamics cortical MEG simultâneas / EEG e anatomicamente constrangido mínima norma-Estimativas: um exemplo Atenção Auditiva

Magneto- and electroencephalography (MEG/EEG) are neuroimaging techniques that provide a high temporal resolution particularly suitable to investigate the ...

mapping-cortical-dynamics-using-simultaneous-megeeg-anatomically

Research

JoVE Journal

Neuroscience

14.5K visualizações.  University of Washington. Usamos magneto-e eletroencefalografia (MEG / EEG), combinado com informações anatômicas capturado por ressonância magnética (MRI), para mapear a dinâmica da rede cortical associado à atenção auditiva.

Vídeo: Mapping Cortical Dynamics Using Simultaneous MEG/EEG and Anatomically-constrained Minimum-norm Estimates: an Auditory Attention Example

Functional Mapping with Simultaneous MEG and EEG

We use magnetoencephalography (MEG) and electroencephalography (EEG) to locate and determine the temporal evolution in brain areas involved in the processing of simple sensory stimuli. We will use somatosensory stimuli to locate the hand somatosensory areas, auditory stimuli to locate the auditory cortices, visual stimuli in four quadrants of the visual field to locate the early visual areas. These type of experiments are used for functional mapping in epileptic and brain tumor patients to locate eloquent cortices. In basic neuroscience similar experimental protocols are used to study the orchestration of cortical activity. The acquisition protocol includes quality assurance procedures, subject preparation for the combined MEG/EEG study, and acquisition of evoked-response data with somatosensory, auditory, and visual stimuli. We also demonstrate analysis of the data using the equivalent current dipole model and cortically-constrained minimum-norm estimates. Anatomical MRI data are employed in the analysis for visualization and for deriving boundaries of tissue boundaries for forward modeling and cortical location and orientation constraints for the minimum-norm estimates.

We use magnetoencephalography (MEG) and electroencephalography (EEG) to map brain areas involved in the processing of simple sensory stimuli.

Mapeamento funcional com MEG e EEG em simultâneo

We use magnetoencephalography (MEG) and electroencephalography (EEG) to locate and determine the temporal evolution in brain areas involved in the ...

Neurociência

Preparation and Culture of Chicken Auditory Brainstem Slices

The chicken auditory brainstem is a well-established model system that has been widely used to study the anatomy and physiology of auditory processing at discreet periods of development 1-4 as well as mechanisms for temporal coding in the central nervous system 5-7.
Here we present a method to prepare chicken auditory brainstem slices that can be used for acute experimental procedures or to culture organotypic slices for long-term experimental manipulations.
The chicken auditory brainstem is composed of nucleus angularis, magnocellularis, laminaris and superior olive. These nuclei are responsible for binaural sound processing and single coronal slice preparations preserve the entire circuitry. Ultimately, organotypic slice cultures can provide the opportunity to manipulate several developmental parameters such as synaptic activity, expression of pre and postsynaptic components, expression of aspects controlling excitability and differential gene expression
This approach can be used to broaden general knowledge about neural circuit development, refinement and maturation.

The chicken auditory brainstem is comprised of nuclei responsible for binaural sound processing. A single coronal slice preparation maintains the entire circuitry while the cultured approach provides a unique preparation to study the development of neuronal structure and auditory function at the molecular, cellular and network levels.

Preparação e Cultura do Fatias de frango auditivo de tronco cerebral

The chicken auditory brainstem is a well-established model system that has been widely used to study the anatomy and physiology of auditory processing at ...

Recording Human Electrocorticographic (ECoG) Signals for Neuroscientific Research and Real-time Functional Cortical Mapping

Neuroimaging studies of human cognitive, sensory, and motor processes are usually based on noninvasive techniques such as electroencephalography (EEG), magnetoencephalography or functional magnetic-resonance imaging. These techniques have either inherently low temporal or low spatial resolution, and suffer from low signal-to-noise ratio and/or poor high-frequency sensitivity. Thus, they are suboptimal for exploring the short-lived spatio-temporal dynamics of many of the underlying brain processes. In contrast, the invasive technique of electrocorticography (ECoG) provides brain signals that have an exceptionally high signal-to-noise ratio, less susceptibility to artifacts than EEG, and a high spatial and temporal resolution (i.e., &lt;1 cm/&lt;1 millisecond, respectively). ECoG involves measurement of electrical brain signals using electrodes that are implanted subdurally on the surface of the brain. Recent studies have shown that ECoG amplitudes in certain frequency bands carry substantial information about task-related activity, such as motor execution and planning1, auditory processing2 and visual-spatial attention3. Most of this information is captured in the high gamma range (around 70-110 Hz). Thus, gamma activity has been proposed as a robust and general indicator of local cortical function1-5. ECoG can also reveal functional connectivity and resolve finer task-related spatial-temporal dynamics, thereby advancing our understanding of large-scale cortical processes. It has especially proven useful for advancing brain-computer interfacing (BCI) technology for decoding a user's intentions to enhance or improve communication6 and control7. Nevertheless, human ECoG data are often hard to obtain because of the risks and limitations of the invasive procedures involved, and the need to record within the constraints of clinical settings. Still, clinical monitoring to localize epileptic foci offers a unique and valuable opportunity to collect human ECoG data. We describe our methods for collecting recording ECoG, and demonstrate how to use these signals for important real-time applications such as clinical mapping and brain-computer interfacing. Our example uses the BCI2000 software platform8,9 and the SIGFRIED10 method, an application for real-time mapping of brain functions. This procedure yields information that clinicians can subsequently use to guide the complex and laborious process of functional mapping by electrical stimulation.
Prerequisites and Planning:
Patients with drug-resistant partial epilepsy may be candidates for resective surgery of an epileptic focus to minimize the frequency of seizures. Prior to resection, the patients undergo monitoring using subdural electrodes for two purposes: first, to localize the epileptic focus, and second, to identify nearby critical brain areas (i.e., eloquent cortex) where resection could result in long-term functional deficits. To implant electrodes, a craniotomy is performed to open the skull. Then, electrode grids and/or strips are placed on the cortex, usually beneath the dura. A typical grid has a set of 8 x 8 platinum-iridium electrodes of 4 mm diameter (2.3 mm exposed surface) embedded in silicon with an inter-electrode distance of 1cm. A strip typically contains 4 or 6 such electrodes in a single line. The locations for these grids/strips are planned by a team of neurologists and neurosurgeons, and are based on previous EEG monitoring, on a structural MRI of the patient's brain, and on relevant factors of the patient's history. Continuous recording over a period of 5-12 days serves to localize epileptic foci, and electrical stimulation via the implanted electrodes allows clinicians to map eloquent cortex. At the end of the monitoring period, explantation of the electrodes and therapeutic resection are performed together in one procedure.
In addition to its primary clinical purpose, invasive monitoring also provides a unique opportunity to acquire human ECoG data for neuroscientific research. The decision to include a prospective patient in the research is based on the planned location of their electrodes, on the patient's performance scores on neuropsychological assessments, and on their informed consent, which is predicated on their understanding that participation in research is optional and is not related to their treatment. As with all research involving human subjects, the research protocol must be approved by the hospital's institutional review board. The decision to perform individual experimental tasks is made day-by-day, and is contingent on the patient's endurance and willingness to participate. Some or all of the experiments may be prevented by problems with the clinical state of the patient, such as post-operative facial swelling, temporary aphasia, frequent seizures, post-ictal fatigue and confusion, and more general pain or discomfort.
At the Epilepsy Monitoring Unit at Albany Medical Center in Albany, New York, clinical monitoring is implemented around the clock using a 192-channel Nihon-Kohden Neurofax monitoring system. Research recordings are made in collaboration with the Wadsworth Center of the New York State Department of Health in Albany. Signals from the ECoG electrodes are fed simultaneously to the research and the clinical systems via splitter connectors. To ensure that the clinical and research systems do not interfere with each other, the two systems typically use separate grounds. In fact, an epidural strip of electrodes is sometimes implanted to provide a ground for the clinical system. Whether research or clinical recording system, the grounding electrode is chosen to be distant from the predicted epileptic focus and from cortical areas of interest for the research. Our research system consists of eight synchronized 16-channel g.USBamp amplifier/digitizer units (g.tec, Graz, Austria). These were chosen because they are safety-rated and FDA-approved for invasive recordings, they have a very low noise-floor in the high-frequency range in which the signals of interest are found, and they come with an SDK that allows them to be integrated with custom-written research software. In order to capture the high-gamma signal accurately, we acquire signals at 1200Hz sampling rate-considerably higher than that of the typical EEG experiment or that of many clinical monitoring systems. A built-in low-pass filter automatically prevents aliasing of signals higher than the digitizer can capture. The patient's eye gaze is tracked using a monitor with a built-in Tobii T-60 eye-tracking system (Tobii Tech., Stockholm, Sweden). Additional accessories such as joystick, bluetooth Wiimote (Nintendo Co.), data-glove (5th Dimension Technologies), keyboard, microphone, headphones, or video camera are connected depending on the requirements of the particular experiment.
Data collection, stimulus presentation, synchronization with the different input/output accessories, and real-time analysis and visualization are accomplished using our BCI2000 software8,9. BCI2000 is a freely available general-purpose software system for real-time biosignal data acquisition, processing and feedback. It includes an array of pre-built modules that can be flexibly configured for many different purposes, and that can be extended by researchers' own code in C++, MATLAB or Python. BCI2000 consists of four modules that communicate with each other via a network-capable protocol: a Source module that handles the acquisition of brain signals from one of 19 different hardware systems from different manufacturers; a Signal Processing module that extracts relevant ECoG features and translates them into output signals; an Application module that delivers stimuli and feedback to the subject; and the Operator module that provides a graphical interface to the investigator.
A number of different experiments may be conducted with any given patient. The priority of experiments will be determined by the location of the particular patient's electrodes. However, we usually begin our experimentation using the SIGFRIED (SIGnal modeling For Realtime Identification and Event Detection) mapping method, which detects and displays significant task-related activity in real time. The resulting functional map allows us to further tailor subsequent experimental protocols and may also prove as a useful starting point for traditional mapping by electrocortical stimulation (ECS).
Although ECS mapping remains the gold standard for predicting the clinical outcome of resection, the process of ECS mapping is time consuming and also has other problems, such as after-discharges or seizures. Thus, a passive functional mapping technique may prove valuable in providing an initial estimate of the locus of eloquent cortex, which may then be confirmed and refined by ECS. The results from our passive SIGFRIED mapping technique have been shown to exhibit substantial concurrence with the results derived using ECS mapping10.
The protocol described in this paper establishes a general methodology for gathering human ECoG data, before proceeding to illustrate how experiments can be initiated using the BCI2000 software platform. Finally, as a specific example, we describe how to perform passive functional mapping using the BCI2000-based SIGFRIED system.

Recording Human Electrocorticographic ECoG Signals for Neuroscientific Research and Real-time Functional Cortical Mapping

We present a method for collecting electrocorticographic signals for research purposes from humans who are undergoing invasive epilepsy monitoring. We show how to use the BCI2000 software platform for data collection, signal processing and stimulus presentation. Specifically, we demonstrate SIGFRIED, a BCI2000-based tool for real-time functional brain mapping.

Gravação Humanos eletrocorticográfica (ECOG) Sinais para pesquisa neurocientífica e mapeamento em tempo real Funcional Cortical

Neuroimaging studies of human cognitive, sensory, and motor processes are usually based on noninvasive techniques such as electroencephalography (EEG), ...

Simultaneous Whole-cell Recordings from Photoreceptors and Second-order Neurons in an Amphibian Retinal Slice Preparation

One of the central tasks in retinal neuroscience is to understand the circuitry of retinal neurons and how those connections are responsible for shaping the signals transmitted to the brain. Photons are detected in the retina by rod and cone photoreceptors, which convert that energy into an electrical signal, transmitting it to other retinal neurons, where it is processed and communicated to central targets in the brain via the optic nerve. Important early insights into retinal circuitry and visual processing came from the histological studies of Cajal1,2 and, later, from electrophysiological recordings of the spiking activity of retinal ganglion cells - the output cells of the retina3,4.
A detailed understanding of visual processing in the retina requires an understanding of the signaling at each step in the pathway from photoreceptor to retinal ganglion cell. However, many retinal cell types are buried deep in the tissue and therefore relatively inaccessible for electrophysiological recording. This limitation can be overcome by working with vertical slices, in which cells residing within each of the retinal layers are clearly visible and accessible for electrophysiological recording.
Here, we describe a method for making vertical sections of retinas from larval tiger salamanders (Ambystoma tigrinum). While this preparation was originally developed for recordings with sharp microelectrodes5,6, we describe a method for dual whole-cell voltage clamp recordings from photoreceptors and second-order horizontal and bipolar cells in which we manipulate the photoreceptor's membrane potential while simultaneously recording post-synaptic responses in horizontal or bipolar cells. The photoreceptors of the tiger salamander are considerably larger than those of mammalian species, making this an ideal preparation in which to undertake this technically challenging experimental approach. These experiments are described with an eye toward probing the signaling properties of the synaptic ribbon - a specialized synaptic structure found in a only a handful of neurons, including rod and cone photoreceptors, that is well suited for maintaining a high rate of tonic neurotransmitter release7,8 - and how it contributes to the unique signaling properties of this first retinal synapse.

We describe the preparation of thin retinal slices from aquatic tiger salamanders (Ambystoma tigrinum) and explain how we use these slices to study synaptic processing in the retina by obtaining dual whole-cell voltage clamp recordings from photoreceptors and second-order horizontal and bipolar cells.

Gravações Whole-cell simultâneas de fotorreceptores e os neurônios de segunda ordem em um anfíbio Retinal Slice Preparação

One of the central tasks in retinal neuroscience  is to understand the circuitry of retinal neurons and how those connections are  responsible for shaping ...

Functional Imaging of Auditory Cortex in Adult Cats using High-field fMRI

Current knowledge of sensory processing in the mammalian auditory system is mainly derived from electrophysiological studies in a variety of animal models, including monkeys, ferrets, bats, rodents, and cats. In order to draw suitable parallels between human and animal models of auditory function, it is important to establish a bridge between human functional imaging studies and animal electrophysiological studies. Functional magnetic resonance imaging (fMRI) is an established, minimally invasive method of measuring broad patterns of hemodynamic activity across different regions of the cerebral cortex. This technique is widely used to probe sensory function in the human brain, is a useful tool in linking studies of auditory processing in both humans and animals and has been successfully used to investigate auditory function in monkeys and rodents. The following protocol describes an experimental procedure for investigating auditory function in anesthetized adult cats by measuring stimulus-evoked hemodynamic changes in auditory cortex using fMRI. This method facilitates comparison of the hemodynamic responses across different models of auditory function thus leading to a better understanding of species-independent features of the mammalian auditory cortex.

Functional studies of the auditory system in mammals have traditionally been conducted using spatially-focused techniques such as electrophysiological recordings. The following protocol describes a method of visualizing large-scale patterns of evoked hemodynamic activity in the cat auditory cortex using functional magnetic resonance imaging.

Imagem Funcional do Cortex Auditivo em gatos adultos usando de alta campo fMRI

Current knowledge of sensory processing in the mammalian auditory system is mainly derived from electrophysiological studies in a variety of animal ...

Optogenetic Stimulation of the Auditory Nerve

Direct electrical stimulation of spiral ganglion neurons (SGNs) by cochlear implants (CIs) enables open speech comprehension in the majority of implanted deaf subjects1-6. Nonetheless, sound coding with current CIs has poor frequency and intensity resolution due to broad current spread from each electrode contact activating a large number of SGNs along the tonotopic axis of the cochlea7-9. Optical stimulation is proposed as an alternative to electrical stimulation that promises spatially more confined activation of SGNs and, hence, higher frequency resolution of coding. In recent years, direct infrared illumination of&#160;the cochlea has been used to evoke responses in the auditory nerve10. Nevertheless it requires higher energies than electrical stimulation10,11 and uncertainty remains as to the underlying mechanism12. Here we describe a method based on optogenetics to stimulate SGNs with low intensity blue light, using transgenic mice with neuronal expression of channelrhodopsin 2 (ChR2)13 or virus-mediated expression of the ChR2-variant CatCh14. We used micro-light emitting diodes (&#181;LEDs) and fiber-coupled lasers to stimulate ChR2-expressing SGNs through a small artificial opening (cochleostomy) or the round window. We assayed the responses by scalp recordings of light-evoked potentials (optogenetic auditory brainstem response: oABR) or by microelectrode recordings from the auditory pathway and compared them with acoustic and electrical stimulation.

Cochlear implants (CIs) enable hearing by direct electrical stimulation of the auditory nerve. However, poor frequency and intensity resolution limits the quality of hearing with CIs. Here we describe optogenetic stimulation of the auditory nerve in mice as an alternative strategy for auditory research and developing future CIs.

A estimulação optogenética do nervo auditivo

Direct electrical stimulation of spiral ganglion neurons (SGNs) by cochlear implants (CIs) enables open speech comprehension in the majority of implanted ...

Touchscreen Sustained Attention Task (SAT) for Rats

Sustained attention is the ability to monitor intermittent and unpredictable events over a prolonged period of time. This attentional process subserves other aspects of cognition and is disrupted in certain neurodevelopmental, neuropsychiatric, and neurodegenerative disorders. Thus, it is clinically important to identify mechanisms that impair and improve sustained attention. Such mechanisms are often first discovered using rodent models. Therefore, several behavior procedures for testing aspects of sustained attention have been developed for rodents. One, first described by McGaughy and Sarter (1995), called the sustained attention task (SAT), trains rats to distinguish between signal (i.e., brief light presentation) and non-signal trials. The signals are short and thus require careful attention to be perceived. Attentional demands can be increased further by introducing a distractor (e.g., flashing houselight). We have modified this task for touchscreen operant chambers, which are configured with a touchscreen on one wall that can present stimuli and record responses. Here we detail our protocol for SAT in touchscreen chambers. Additionally, we present standard measures of performance in male and female Sprague-Dawley rats. Comparable performance on this task in both sexes highlights its use for attention studies, especially as more researchers are including female rodents in their experimental design. Moreover, the easy implementation of SAT for the increasingly popular touchscreen chambers increases its utility.

Touchscreen Sustained Attention Task SAT for Rats

Sustained attention, or continuously monitoring situations for intermittent and unpredictable events, is a critical aspect of cognition. Here we detail how to test sustained attention in rats using touchscreen operant chambers. We demonstrate comparable performance in male and female rats, making this task useful for studying attention in both sexes.

Touchscreen sustentada atenção tarefa (SAT) para ratos

Sustained attention is the ability to monitor intermittent and unpredictable events over a prolonged period of time. This attentional process subserves ...

Simultaneous Recordings of Cortical Local Field Potentials, Electrocardiogram, Electromyogram, and Breathing Rhythm from a Freely Moving Rat

Monitoring the physiological dynamics of the brain and peripheral tissues is necessary for addressing a number of questions about how the brain controls body functions and internal organ rhythms when animals are exposed to emotional challenges and changes in their living environments. In general experiments, signals from different organs, such as the brain and the heart, are recorded by independent recording systems that require multiple recording devices and different procedures for processing the data files. This study describes a new method that can simultaneously monitor electrical biosignals, including tens of local field potentials in multiple brain regions, electrocardiograms that represent the cardiac rhythm, electromyograms that represent awake/sleep-related muscle contraction, and breathing signals, in a freely moving rat. The recording configuration of this method is based on a conventional micro-drive array for cortical local field potential recordings in which tens of electrodes are accommodated, and the signals obtained from these electrodes are integrated into a single electrical board mounted on the animal's head. Here, this recording system was improved so that signals from the peripheral organs are also transferred to an electrical interface board. In a single surgery, electrodes are first separately implanted into the appropriate body parts and the target brain areas. The open ends of all of these electrodes are then soldered to individual channels of the electrical board above the animal's head so that all of the signals can be integrated into the single electrical board. Connecting this board to a recording device allows for the collection of all of the signals into a single device, which reduces experimental costs and simplifies data processing, because all data can be handled in the same data file. This technique will aid the understanding of the neurophysiological correlates of the associations between central and peripheral organs.

This study introduces a method for the simultaneous recording of local field potentials in the brain, electrocardiograms, electromyograms, and breathing signals of a freely moving rat. This technique, which reduces experimental costs and simplifies data analysis, will contribute to the understanding of the interactions between the brain and peripheral organs.

Gravações simultâneas de potenciais de campo corticais Local, eletrocardiograma, eletromiograma e respirar o ritmo de um rato andando livremente

Monitoring the physiological dynamics of the brain and peripheral tissues is necessary for addressing a number of questions about how the brain controls ...

Rat Model of Widespread Cerebral Cortical Demyelination Induced by an Intracerebral Injection of Pro-Inflammatory Cytokines

Multiple sclerosis (MS) is the most common immune-mediated disease of the central nervous system (CNS) and progressively leads to physical disability and death, caused by white matter lesions in the spinal cord and cerebellum, as well as by demyelination in grey matter. Whilst conventional models of experimental allergic encephalomyelitis are suitable for the investigation of the cell-mediated inflammation in the spinal and cerebellar white matter, they fail to address grey matter pathologies. Here, we present the experimental protocol for a novel rat model of cortical demyelination allowing the investigation of the pathological and molecular mechanisms leading to cortical lesions. The demyelination is induced by an immunization with low-dose myelin oligodendrocyte glycoprotein (MOG) in an incomplete Freund&#39;s adjuvant followed by a catheter-mediated intracerebral delivery of pro-inflammatory cytokines. The catheter, moreover, enables multiple rounds of demyelination without causing injection-induced trauma, as well as the intracerebral delivery of potential therapeutic drugs undergoing a preclinical investigation. The method is also ethically favorable as animal pain and distress or disability are controlled and relatively minimal. The expected timeframe for the implementation of the entire protocol is around 8 - 10 weeks.

The protocol presented here allows the reproduction of a widespread grey matter demyelination of both cortical hemispheres in adult male Dark Agouti rats. The method comprises of intracerebral implantation of a catheter, subclinical immunization against myelin oligodendrocyte glycoprotein, and intracerebral injection of a pro-inflammatory cytokine mixture through the implanted catheter.

Modelo de Rato de Demyelinação Cortical Cerebral Generalizada Induzida por uma injeção intracerebral de citocinas pró-inflamatórias

Multiple sclerosis (MS) is the most common immune-mediated disease of the central nervous system (CNS) and progressively leads to physical disability and ...

Statistical Modelling of Cortical Connectivity Using Non-invasive Electroencephalograms

Non-invasive electrophysiological recordings are useful for the evaluation of nervous system function. These techniques are inexpensive, fast, replicable, and less resource-intensive than imaging. Further, the functional data produced have excellent temporal resolution, which is not achievable with structural imaging.
Current applications of electroencephalograms (EEG) are limited by data processing methods. Standard analysis techniques using raw time series data at individual channels are very limited methods of interrogating nervous system activity. More detailed information about cortical function can be achieved by examining relationships between channels and deriving statistical models of how areas are interacting, allowing visualization of connectivity between networks.
This manuscript describes a method for deriving statistical models of cortical network activity by recording EEG in a standard manner, then examining the interelectrode coherence measures to assess relationships between the recorded areas. Higher order interactions can be further examined by assessing the covariance between the coherence pairs, producing high-dimensional &#34;maps&#34; of network interactions. These data constructs can be examined to assess cortical network function and its relationship to pathology in ways not achievable with traditional techniques.
This approach offers greater sensitivity to network level interactions than is achievable with raw time series analysis. It is, however, limited by the complexity of drawing specific mechanistic conclusions about the underlying neural populations and the high volumes of data generated, requiring more advanced statistical techniques for evaluation, including dimensionality reduction and classifier-based approaches.

Standard EEG analysis techniques offer limited insight into nervous system function. Deriving statistical models of cortical connectivity offers far greater ability to investigate underlying network dynamics. Improved functional assessment opens new possibilities for diagnosis, prognostication, and outcome prediction in nervous system diseases.

Modelagem estatística da conectividade cortical usando eletroencefalogramas não invasivos

Non-invasive electrophysiological recordings are useful for the evaluation of nervous system function. These techniques are inexpensive, fast, replicable, ...