Ce travail a été rendu possible par des subventions soutenues par le Bureau US Army Research (W911NF-07-1-0415 (GS), W911NF-08-1-0216 (GS)) et le (NIH / NIBIB EB006356 (GS) et EB00856 ( JRW et GS)). Les auteurs tiennent à remercier Sean Austin pour le module SigfriedSigProcLAVA, et Griffin Milsap pour l&#39;assistance technique connexe.

1. Localisation des électrodes <ol><li> Prélever un pré-opératoire pondérée en T1 IRM structurelle (1.5T ou 3T) de la tête du patient: 256 x 256 pixels par tranche, sur le terrain plein de vue, aucune interpolation, 1 tranche de largeur mm, de préférence les coupes sagittales. </li><li> Observer l&#39;implantation chirurgicale des grilles et des bandes. Recueillir des photos numériques des électrodes in situ, et les notes du neurochirurgien sur les emplacements des grilles et des bandes implantées. </li><li> Recueillir les post-opératoires radiographie du crâne et le cerveau des images tomodensitométrie à haute résolution (1 mm largeur de la tranche, peau à peau, pas d&#39;angle). </li><li> Créer un modèle tridimensionnel corticale du cerveau du patient à l&#39;aide de l&#39;IRM pré-opératoire, et co-enregistrer avec les images post-implantation de la grille CT. Nous utilisons le logiciel CURRY à cet effet, et d&#39;exporter la structure 3D corticale et l&#39;électrode coordonne au format MATLAB. À partir de MATLAB, nous exportons un film qui montre les électrodes mappés sur le cerveau. Nous aussi MAP coordonne l&#39;électrode de standards aires de Brodmann l&#39;aide d&#39;un atlas de Talairach automatisé. </li><li> Vérifiez les informations à partir du modèle 3D, X-ray images, des photographies et des notes. Finaliser un schéma de numérotation pour les électrodes, et le travail avec les techniciens des hôpitaux afin de s&#39;assurer que les électrodes sont patchés dans la répartiteurs suite à cette numérotation exactement. Également créer un plan schématique pour tracer les électrodes en deux dimensions, tels que tous les postes d&#39;électrodes peuvent être clairement distingués, sans chevauchement. Si vous allez courir Sigfried (voir section 4), à l&#39;exception de ces coordonnées à deux dimensions comme un fragment BCI2000 paramètre, dans le format requis par le paramètre ElectrodeLocations. Enfin, sélectionnez deux emplacements des électrodes qui sont susceptibles d&#39;être electrocorticographically «silencieuse», c&#39;est à dire qu&#39;ils ne sont pas près de le cortex éloquent présumée, à utiliser comme un motif initial et de référence (préparer les g.USBamps par rapiéçage la référence aux sockets bleus, et au solaux prises jaunes, sur l&#39;extrême droite de chaque unité). </li></ol> 2. Configuration matérielle et logicielle <ol><li> Assurez-vous que les spécifications de l&#39;ordinateur sont suffisantes pour traiter les exigences de traitement de l&#39;expérience. Un processeur multi-core sera probablement nécessaire pour répondre aux demandes en temps réel de l&#39;acquisition de données et le traitement, l&#39;enregistrement vidéo, et d&#39;autres tâches nécessaires. Pour l&#39;enregistrement et analyse en temps réel de 128 canaux à 1200 Hz, nous utilisons un 3-GHz quad-core machine avec 4 Go de RAM. Les amplificateurs doivent être connectés à un contrôleur USB dédié, distinct du contrôleur (s) utilisé par d&#39;autres périphériques gourmands en bande passante, tels que des disques durs externes et les appareils photo (cela peut être vérifié par l&#39;intermédiaire du Gestionnaire de périphériques du système). Enfin, il doit y avoir suffisamment d&#39;espace disque pour stocker un maximum de 5 Mo par seconde de données expérimentales, et un système d&#39;archivage et de les sauvegarder. </li><li> Mettre en place le matériel de recherche (amplificateurs, ordinateur, écran expérimentateur, Keyboard, haut-parleurs, microphone et la caméra) sur un seul chariot, qui peut être déployée rapidement dans et hors de la chambre du patient, avec seulement un cordon d&#39;alimentation unique à brancher dans le mur. Pour déplacer l&#39;ordinateur d&#39;une pièce à, utilisez la fonction Mise en veille prolongée avant de le débrancher. Écran vidéo Le patient doit être sur un plateau de table séparée ou bras de moniteur. Considérant que le patient est sujet à des crises, assurez-vous que tout le matériel peut être sorti de la voie rapide en cas besoin de personnel médical un accès immédiat pour le patient. Le matériel doit également être désinfectés avec des lingettes antiseptiques avant et après utilisation dans la chambre du patient. </li><li> Temps avec le patient est limitée, et toutes les procédures doivent être robustes et optimisées pour tirer le meilleur parti de ce moment-là. À cet égard, la flexibilité et la robustesse de BCI2000 sont des caractéristiques précieuses. Assurez-vous que les expériences peuvent être lancés à la pression d&#39;un bouton. Dans le cas de BCI2000, utiliser un fichier batch pour lancer la bonne combinaison deBCI2000 modules automatiquement, avec le ligne de commande requis des options. L&#39;opérateur et les modules gUSBampSource sont nécessaires, avec le Traitementdusignal appropriée et des modules d&#39;application pour votre expérience particulière. Utilisez la fonction de l&#39;opérateur BCI2000 de script pour faire en sorte que tous les fichiers de paramètres requis sont automatiquement chargés, y compris celles qui sont spécifiques à ce patient, tels que le nombre d&#39;électrodes et de leurs noms et qualités. Le but de cette automatisation est de minimiser le nombre d&#39;étapes manuelles par l&#39;expérimentateur, et donc les possibilités d&#39;erreur. Le logiciel et ses paramètres doivent avoir été finalisé et testé (avec peut-être un sujet EEG) au moins une ou deux semaines avant l&#39;implantation. Il est également fortement conseillé d&#39;effectuer un &quot;sec&quot; trajet le jour précédant la première session expérimentale, y compris tous les nouveaux patients des paramètres spécifiques. </li></ol> 3. Session expérimentale Set-up <ol><li> Choisissez votre moment poursuggérant des enregistrements expérimentaux pour le patient, en leur donnant remarquerez tôt dans la journée, et encore 15 minutes avant de commencer. Contourner les visiteurs, les repas, les siestes, les procédures médicales et physique du patient, l&#39;état émotionnel et cognitif. Il est important d&#39;établir un rapport avec le personnel médical sur le sol, pour aider à optimiser la synchronisation et la durée des enregistrements. </li><li> Roue de l&#39;équipement en place, se connecter à la prise de courant, tournez sur l&#39;écran vidéo du sujet et le connecter à l&#39;ordinateur, et non en veille prolongée l&#39;ordinateur. </li><li> Lancement BCI2000. Avec le paramètre VisualizeSource activé, appuyez sur Set Config. Le spectateur signal ouvre, vous laissant apprécier la qualité du signal ECoG. Cliquez-droit sur le spectateur et régler le filtre passe-haut à un seuil de 5 Hz. (Ce réglage du filtre affectera seulement la visualisation, et non la collecte de données.) </li><li> Vérifiez les interférences du bruit de ligne électrique: Est-ce l&#39;activation d&#39;un filtre coupe-bande dans la visionneuse (à 50 Hz ou 60 Hz,selon le pays où vous vous trouvez) faire une grande différence pour le signal? Si c&#39;est le cas, essayez de réduire cela en supprimant tout montant inutilisé du cross-parler câbles, ou à identifier et éliminer les autres sources de puissance d&#39;interférence. Changer les électrodes utilisées à titre de référence et la masse si nécessaire. </li><li> Si vous utilisez un eye-tracker, le calibrer en utilisant le logiciel de calibration fourni par le fabricant. Le module BCI2000 source doit être compilé avec l&#39;extension EyetrackerLogger inclus, et devrait être lancé avec l&#39;option - LogEyetracker = 1 indicateur est activé, de sorte que l&#39;œil les données de suivi peuvent être acquises en phase avec les signaux ECOG. </li><li> Pour éviter les distractions et les interruptions, et de minimiser les interférences possibles, veiller à ce que les téléviseurs, les radios et les téléphones mobiles sont éteints. </li><li> Donner des instructions précises au patient pour l&#39;expérience, vous êtes sur le point de fonctionner. Selon la tâche du sujet, préparé des diapositives Powerpoint qui montrent la tâche, la posture a suggéré, etc, peuvent se révéler utiles. </li&gt; <li> Appuyez sur Démarrer sur la console pour démarrer l&#39;expérience. Chaque fois que vous appuyez sur Démarrer ou Reprendre, un nouveau fichier sera créé pour éviter d&#39;écraser les données précédentes, et le fichier sera initialisé avec une copie de toutes les valeurs des paramètres. Les données brutes seront ensuite écoutés automatiquement dans le fichier, ainsi que des marqueurs d&#39;événements, jusqu&#39;à ce que vous appuyez sur Pause ou les finitions terme expérimentales. </li><li> Tout au long de la session, de surveiller le comportement du patient et les signaux pour les convulsions ECOG suspects, et être prêt à réagir à des instructions du personnel médical. </li></ol> 4. Session Exemple expérimental: Sigfried cartographie clinique avec BCI2000 <ol><li> Préparation: Avant le début de la session, vous aurez besoin d&#39;avoir préparé un dossier model.ini qui contient les paramètres de traitement du signal Sigfried va utiliser pour construire un modèle, et un fichier prm (ou séparée des fragments PRM.) Contenant les paramètres que BCI2000. le module SigfriedSigProcva utiliser pour visualisation en temps réel. Deux paramètres principaux sont ElectrodeLocations, précisant la mise en page 2-D que vous avez choisi pour les électrodes particulières de ce patient, et ElectrodeCondition, qui spécifie les différentes tâches seront cartographiés dans quelles conditions. Dans cet exemple, nous utilisons le module StimulusPresentation simple pour communiquer des instructions au patient, afin que le paramètre stimuli doit également être adaptée aux tâches que nous l&#39;intention de courir. </li><li> Étape de base: Début des modules gUSBampSource, DummySignalProcessing et StimulusPresentationTask, configurés à l&#39;activité de l&#39;échantillon ECoG toutes les grilles et les bandes à 1200Hz, passe-haut-filtré à 0,1 Hz. Demander au sujet de se relaxer et de rester immobile, les yeux ouverts. Enregistrement de 6 minutes d&#39;activité de base, sous un éclairage à l&#39;aise dans un environnement calme. </li><li> Étape de la modélisation: Démarrez l&#39;outil data2model_gui et extraire des caractéristiques dans les bacs Hz 5 from 70 à 110 Hz en utilisant au maximum la méthode d&#39;entropie pour toutes les 500 ms de données. Appuyez sur Construire le modèle pour construire un modèle probabiliste des caractéristiques spectrales sélectionnées en utilisant des mélanges gaussiens. </li><li> Étape de cartographie: Démarrez le gUSBampSource, SigfriedSigProcLAVA et modules StimulusPresentationTask et configurer l&#39;opérateur de charger le modèle probabiliste, le modèle cortical, et le 2 - et les coordonnées d&#39;électrodes 3-dimensions. Après avoir demandé le sujet, commencer le processus de cartographie. Dans ce processus, d&#39;un sujet ne exécution de chaque tâche pendant 10 secondes à la fois, sur chacun de 5 répétitions. Au cours de chaque tâche, Sigfried détecte une activité ECoG tâche liée qui est présenté en 2 continuellement mis à jour - et 3-dimensions des cartes du cortex éloquent. Dans les cartes en 2 dimensions, la taille et la rougeur de chaque cercle représente son importance dans cette tâche particulière. Plus précisément, la taille de chaque cercle est proportionnelle à la fraction de la variance totale du signal dans le ba gammae qui est représenté par la tâche. Cette statistique est connue comme le coefficient de détermination, ou R 2. Il est dans la gamme (0,1) et dans la configuration actuelle d&#39;une valeur de 0,1 peut généralement être considérée comme significative. La mise à l&#39;échelle des cercles à un maximum de valeurs de r 2 peut être contrôlé à l&#39;aide des curseurs (voir la figure 1C). Dans les cartes en 3 dimensions, les valeurs de R 2 sont mis en correspondance avec des couleurs différentes, plutôt que les tailles de cercle. </li></ol> 5. Les résultats représentatifs La figure 1 montre des résultats représentatifs, d&#39;une séance de cartographie Sigfried chez un patient. Le patient était un homme de 28 ans droitier femme qui avait intraitable localisation liée à l&#39;épilepsie de gauche-temporelle avec l&#39;apparition généralisation secondaire. 120 électrodes ont été implantées sous-durale electrocorticographic plus à gauche frontal, pariétal et le cortex temporal. Une radiographie latérale (partie A) et une photographie intra-opératoire (groupe B) représentent laconfiguration d&#39;un réseau frontale avec 40 électrodes, une densité plus élevée de la grille temporelle avec 68 électrodes, et trois bandes chacune de 4 électrodes. A partir des saisies enregistrées, un neurologue localisé le foyer épileptique et a déterminé qu&#39;il était nécessaire d&#39;effectuer une résection chirurgicale du lobe temporal gauche, tout en épargnant le cortex langage éloquent. Ceci a été réalisé avec succès: à 8 mois après résection du patient a été évalué comme la saisie libre et sans déficits neurologiques. La procédure de cartographie passive Sigfried cortex identifiés impliqués dans la fonction du langage en comparant les tâches liées à des changements au cours de tâches d&#39;écoute. Les résultats ont été présentés dans deux interfaces: une interface en 2 dimensions (panneau C), ce qui rend la disposition des électrodes clair, et une interface en 3 dimensions anatomiquement correcte (panneau D). De gauche à droite le contraste panneaux écoute de la langue parlée de base vs (VOICE), qui entend des sons de base vs (TONS), et écouter de la langue parlée vs lisTening aux tonalités (langue). Le dernier d&#39;entre eux est incluse comme une image approximative de la fonction auditive qui est spécifique à langage réceptif. Les résultats de la condition VOIX montré une bonne concordance avec les emplacements au cours de laquelle ECS perturbé la fonction du langage réceptif chez ce patient (marqué par des cercles jaunes dans la partie A). <img alt="Figure 1" src="/files/ftp_upload/3993/3993fig1.jpg" /> Figure 1. Exemple de résultats d&#39;un patient. Panel A montre une radiographie latérale. Cercles jaunes marquent les électrodes impliquées dans le langage réceptif, comme la suite été identifiés par la cartographie de stimulation électrocorticale. Groupe B est une photographie prise lors de l&#39;implantation. Groupe C montre les résultats de la cartographie Sigfried dans un schéma à deux dimensions mise en page: la taille et la rougeur de chaque disque représente l&#39;importance de l&#39;implication de chaque électrode dans la tâche, par rapport au scénario de référence. Dans le panneau D, la même statistique est associée à la couleur sur un Rende tridimensionnelle du cerveau modèlerouge à partir de l&#39;IRM du patient.

<ol>
	<li>Miller, K. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spectral+Changes+in+Cortical+Surface+Potentials+during+Motor+Movement.">Spectral Changes in Cortical Surface Potentials during Motor Movement.</a> Journal of Neuroscience. 27, 2424-2424 (2007).</li><li>Chang, E. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Categorical+speech+representation+in+human+superior+temporal+gyrus.">Categorical speech representation in human superior temporal gyrus.</a> Nature Neuroscience. 13, 1428-1428 (2010).</li><li>Gunduz, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+correlates+of+visual-spatial+attention+in+electrocorticographic+signals+in+humans.">Neural correlates of visual-spatial attention in electrocorticographic signals in humans.</a> Frontiers in Human Neuroscience. 5, (2011).</li><li>Pei, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatiotemporal+dynamics+of+electrocorticographic+high+gamma+activity+during+overt+and+covert+word+repetition.">Spatiotemporal dynamics of electrocorticographic high gamma activity during overt and covert word repetition.</a> NeuroImage. 54, 2960 (2010).</li><li>Crone, N. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-frequency+gamma+oscillations+and+human+brain+mapping+with+electrocorticography.">High-frequency gamma oscillations and human brain mapping with electrocorticography.</a> Progress in Brain Research. 159, 275 (2006).</li><li>Brunner, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+communication+with+a+"P300"+matrix+speller+using+electrocorticographic+signals+(ECoG).">Rapid communication with a "P300" matrix speller using electrocorticographic signals (ECoG).</a> Frontiers in Neuroprosthetics. 5, (2010).</li><li>Leuthardt, E. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+brain-computer+interface+using+electrocorticographic+signals+in+humans.">A brain-computer interface using electrocorticographic signals in humans.</a> Journal of Neural Engineering. 1, (2004).</li><li>Schalk, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=BCI2000:+A+General-Purpose+Brain-Computer+Interface+(BCI)+System.">BCI2000: A General-Purpose Brain-Computer Interface (BCI) System.</a> IEEE Transactions in Biomedical Engineering. 51, 1034 (2004).</li><li>Schalk, G., Mellinger, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> A Practical Guide to Brain-Computer Interfacing with BCI2000. , (2010).</li><li>Brunner, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+practical+procedure+for+real-time+functional+mapping+of+eloquent+cortex+using+electrocorticographic+signals+in+humans.">A practical procedure for real-time functional mapping of eloquent cortex using electrocorticographic signals in humans.</a> Epilepsy and Behavior. 15, 278 (2009).</li></ol>

Pas de conflits d&#39;intérêt déclarés.

Collecte de données pour la recherche ECOG exige une coopération étroite entre les cliniciens et les chercheurs, avec une très équipe multi-disciplinaire résoudre les problèmes en neurologie clinique, neurochirurgie, des neurosciences fondamentales, informatique et génie électrique. La récompense est que les signaux ECOG, et des amplitudes particulières dans la gamme de fréquences haute gamma (70-110Hz), sont de grande valeur. Non seulement ils donnent un aperçu scientifique sur les corrélats neuraux de la...

<ol><li> 8 x 16 canaux amplificateurs g.USBamp ( <a href="http://gtec.at" target="_blank">http://gtec.at</a> ) </li><li> 2 x 64 canaux break-out box (séparateur caisse de tête) </li><li> 2 Câble de raccordement x de diviseur au système clinique </li><li> 2 Câble de raccordement x de diviseur à quatre g.USBamps </li><li> 2 x adaptateur d&#39;alimentation à quatre voies pour quatre g.USBamps </li><li> 2 x adaptateur de synchronisation à quatre voies pour synchroniser quatre g.USBamps </li><li> 1 x câble de synchronisation pour synchroniser deux ensembles de quatre g.USBamps </li><li> 1 x potentiel de péréquation pince + câble pour g.USBamp </li><li> 18 x câbles cavaliers Touchproof </li><li> 2 x quatre voies concentrateurs USB 2.0 </li><li> Bloc d&#39;alimentation </li><li> Ordinateur portable ou de bureau (voir la section 2.1) </li><li> Sécurisé, chariot mobile pour l&#39;ensemble de ce qui précède </li><li> Oculomètre (ou moniteur LCD ordinaire) pour le patient </li><li> Tablette amovible pour le moniteur patient </li><li> D&#39;autres périphériques (manettes de jeu, etc) pour les patients des réponses comportementales </li><li> BCI2000 logiciels </li><li> CUrry logiciels </li><li> Logiciel MATLAB </li></ol>

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.

Watch this Scientific Journal Video about Recording Human Electrocorticographic ECoG Signals for Neuroscientific Research and Real-time Functional Cortical Mapping at JoVE.com

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

Nous présentons une méthode pour collecter des signaux electrocorticographic des fins de recherche de l&#39;homme qui sont en cours de surveillance d&#39;épilepsie invasive. Nous montrons comment utiliser la plate-forme BCI2000 logiciels pour la collecte des données, traitement du signal et la présentation du stimulus. Plus précisément, nous démontrons Sigfried, un outil basé sur BCI2000 en temps réel la cartographie fonctionnelle du cerveau.

Enregistrement de l&#39;homme (Electrocorticographic ECoG) Signaux pour la recherche neuroscientifique et en temps réel la cartographie fonctionnelle corticale

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

recording-human-electrocorticographic-ecog-signals-for

Research

JoVE Journal

Neuroscience

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

25.5K vues.  New York State Department of Health. Nous présentons une méthode pour collecter des signaux electrocorticographic des fins de recherche de l'homme qui sont en cours de surveillance d'épilepsie invasive. Nous montrons comment utiliser la plate-forme BCI2000 logiciels pour la collecte des données, traitement du signal et la présentation du stimulus. Plus précisément, nous démontrons Sigfried, un outil basé sur BCI2000 en temps réel la cartographie fonctionnelle du cerveau.

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

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.

Cartographie fonctionnelle avec MEG et EEG simultanée

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

Recherche

Neurosciences

Correlating Behavioral Responses to fMRI Signals from Human Prefrontal Cortex: Examining Cognitive Processes Using Task Analysis

The aim of this methods paper is to describe how to implement a neuroimaging technique to examine complementary brain processes engaged by two similar tasks. Participants' behavior during task performance in an fMRI scanner can then be correlated to the brain activity using the blood-oxygen-level-dependent signal. We measure behavior to be able to sort correct trials, where the subject performed the task correctly and then be able to examine the brain signals related to correct performance. Conversely, if subjects do not perform the task correctly, and these trials are included in the same analysis with the correct trials we would introduce trials that were not only for correct performance. Thus, in many cases these errors can be used themselves to then correlate brain activity to them. We describe two complementary tasks that are used in our lab to examine the brain during suppression of an automatic responses: the stroop1 and anti-saccade tasks. The emotional stroop paradigm instructs participants to either report the superimposed emotional 'word' across the affective faces or the facial 'expressions' of the face stimuli1,2. When the word and the facial expression refer to different emotions, a conflict between what must be said and what is automatically read occurs. The participant has to resolve the conflict between two simultaneously competing processes of word reading and facial expression. Our urge to read out a word leads to strong 'stimulus-response (SR)' associations; hence inhibiting these strong SR's is difficult and participants are prone to making errors. Overcoming this conflict and directing attention away from the face or the word requires the subject to inhibit bottom up processes which typically directs attention to the more salient stimulus. Similarly, in the anti-saccade task3,4,5,6, where an instruction cue is used to direct only attention to a peripheral stimulus location but then the eye movement is made to the mirror opposite position. Yet again we measure behavior by recording the eye movements of participants which allows for the sorting of the behavioral responses into correct and error trials7 which then can be correlated to brain activity. Neuroimaging now allows researchers to measure different behaviors of correct and error trials that are indicative of different cognitive processes and pinpoint the different neural networks involved.

The goal of our research is to correlate behavior to brain activity. Accurate behavioral measures and imaging techniques allow us to elucidate brain-behavior relationships.

Corrélation entre réponses comportementales aux signaux IRMf de cortex préfrontal humain: l&#39;examen des processus cognitifs en utilisant l&#39;analyse des tâches

The aim of this methods paper is to describe how to implement a neuroimaging technique to examine complementary brain processes engaged by two similar ...

Functional Calcium Imaging in Developing Cortical Networks

A hallmark pattern of activity in developing nervous systems is spontaneous, synchronized network activity. Synchronized activity has been observed in intact spinal cord, brainstem, retina, cortex and dissociated neuronal culture preparations. During periods of spontaneous activity, neurons depolarize to fire single or bursts of action potentials, activating many ion channels. Depolarization activates voltage-gated calcium channels on dendrites and spines that mediate calcium influx. Highly synchronized electrical activity has been measured from local neuronal networks using field electrodes. This technique enables high temporal sampling rates but lower spatial resolution due to integrated read-out of multiple neurons at one electrode. Single cell resolution of neuronal activity is possible using patch-clamp electrophysiology on single neurons to measure firing activity. However, the ability to measure from a network is limited to the number of neurons patched simultaneously, and typically is only one or two neurons. The use of calcium-dependent fluorescent indicator dyes has enabled the measurement of synchronized activity across a network of cells. This technique gives both high spatial resolution and sufficient temporal sampling to record spontaneous activity of the developing network.
A key feature of newly-forming cortical and hippocampal networks during pre- and early postnatal development is spontaneous, synchronized neuronal activity (Katz &amp; Shatz, 1996; Khaziphov &amp; Luhmann, 2006). This correlated network activity is believed to be essential for the generation of functional circuits in the developing nervous system (Spitzer, 2006). In both primate and rodent brain, early electrical and calcium network waves are observed pre- and postnatally in vivo and in vitro (Adelsberger et al., 2005; Garaschuk et al., 2000; Lamblin et al., 1999). These early activity patterns, which are known to control several developmental processes including neuronal differentiation, synaptogenesis and plasticity (Rakic &amp; Komuro, 1995; Spitzer et al., 2004) are of critical importance for the correct development and maturation of the cortical circuitry.
In this JoVE video, we demonstrate the methods used to image spontaneous activity in developing cortical networks. Calcium-sensitive indicators, such as Fura 2-AM ester diffuse across the cell membrane where intracellular esterase activity cleaves the AM esters to leave the cell-impermeant form of indicator dye. The impermeant form of indicator has carboxylic acid groups which are able to then detect and bind calcium ions intracellularly.. The fluorescence of the calcium-sensitive dye is transiently altered upon binding to calcium. Single or multi-photon imaging techniques are used to measure the change in photons being emitted from the dye, and thus indicate an alteration in intracellular calcium. Furthermore, these calcium-dependent indicators can be combined with other fluorescent markers to investigate cell types within the active network.

Spontaneous activity of developing neuronal networks can be measured using AM-ester forms of calcium-sensitive indicator dyes. Changes in intracellular calcium, indicating neuronal activation, are detected as transient changes in indicator fluorescence with one- or two-photon imaging. This protocol can be adapted for a range of developmentally-dependent neuronal networks in vitro.

Imagerie fonctionnelle en calcium développement des réseaux corticaux

A hallmark pattern of activity in developing nervous systems is spontaneous, synchronized network activity. Synchronized activity has been observed in ...

Surgical Implantation of Chronic Neural Electrodes for Recording Single Unit Activity and Electrocorticographic Signals

The success of long-term electrophysiological recordings often depends on the quality of the implantation surgery. Here we provide useful information for surgeons who are learning the process of implanting electrode systems. We demonstrate the implantation procedure of both a penetrating and a surface electrode. The surgical process is described from start to finish, including detailed descriptions of each step throughout the procedure. It should also be noted that this video guide is focused towards procedures conducted in rodent models and other small animal models. Modifications of the described procedures are feasible for other animal models.

We provide useful information for surgeons who are learning the process of implanting chronic neural recording electrodes. Techniques for both penetrating and surface electrode systems are described in a rodent animal model.

L&#39;implantation chirurgicale d&#39;électrodes neurales chroniques pour l&#39;enregistrement d&#39;activité Unité unique et Signaux Electrocorticographic

The success of long-term electrophysiological recordings often depends on the quality of the implantation surgery.  Here we provide useful information for ...

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

Magneto- and electroencephalography (MEG/EEG) are neuroimaging techniques that provide a high temporal resolution particularly suitable to investigate the cortical networks involved in dynamical perceptual and cognitive tasks, such as attending to different sounds in a cocktail party. Many past studies have employed data recorded at the sensor level only, i.e., the magnetic fields or the electric potentials recorded outside and on the scalp, and have usually focused on activity that is time-locked to the stimulus presentation. This type of event-related field / potential analysis is particularly useful when there are only a small number of distinct dipolar patterns that can be isolated and identified in space and time. Alternatively, by utilizing anatomical information, these distinct field patterns can be localized as current sources on the cortex. However, for a more sustained response that may not be time-locked to a specific stimulus (e.g., in preparation for listening to one of the two simultaneously presented spoken digits based on the cued auditory feature) or may be distributed across multiple spatial locations unknown a priori, the recruitment of a distributed cortical network may not be adequately captured by using a limited number of focal sources.
Here, we describe a procedure that employs individual anatomical MRI data to establish a relationship between the sensor information and the dipole activation on the cortex through the use of minimum-norm estimates (MNE). This inverse imaging approach provides us a tool for distributed source analysis. For illustrative purposes, we will describe all procedures using FreeSurfer and MNE software, both freely available. We will summarize the MRI sequences and analysis steps required to produce a forward model that enables us to relate the expected field pattern caused by the dipoles distributed on the cortex onto the M/EEG sensors. Next, we will step through the necessary processes that facilitate us in denoising the sensor data from environmental and physiological contaminants. We will then outline the procedure for combining and mapping MEG/EEG sensor data onto the cortical space, thereby producing a family of time-series of cortical dipole activation on the brain surface (or "brain movies") related to each experimental condition. Finally, we will highlight a few statistical techniques that enable us to make scientific inference across a subject population (i.e., perform group-level analysis) based on a common cortical coordinate space.

We use magneto- and electroencephalography (MEG/EEG), combined with anatomical information captured by magnetic resonance imaging (MRI), to map the dynamics of the cortical network associated with auditory attention.

Cartographie dynamique corticales à l&#39;aide MEG / EEG simultanés et anatomique contrainte minimum-norm Budget: un exemple L&#39;attention auditive

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

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.

Imagerie fonctionnelle du cortex auditif chez chats adultes à l&#39;aide de haut-champ IRMf

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

A Protocol for the Administration of Real-Time fMRI Neurofeedback Training

Neurologic disorders are characterized by abnormal cellular-, molecular-, and circuit-level functions in the brain. New methods to induce and control neuroplastic processes and correct abnormal function, or even shift functions from damaged tissue to physiologically healthy brain regions, hold the potential to dramatically improve overall health. Of the current neuroplastic interventions in development, neurofeedback training (NFT) from functional Magnetic Resonance Imaging (fMRI) has the advantages of being completely non-invasive, non-pharmacologic, and spatially localized to target brain regions, as well as having no known side effects. Furthermore, NFT techniques, initially developed using fMRI, can often be translated to exercises that can be performed outside of the scanner without the aid of medical professionals or sophisticated medical equipment. In fMRI NFT, the fMRI signal is measured from specific regions of the brain, processed, and presented to the participant in real-time. Through training, self-directed mental processing techniques, that regulate this signal and its underlying neurophysiologic correlates, are developed. FMRI NFT has been used to train volitional control over a wide range of brain regions with implications for several different cognitive, behavioral, and motor systems. Additionally, fMRI NFT has shown promise in a broad range of applications such as the treatment of neurologic disorders and the augmentation of baseline human performance. In this article, we present an fMRI NFT protocol developed at our institution for modulation of both healthy and abnormal brain function, as well as examples of using the method to target both cognitive and auditory regions of the brain.

The ability to induce and/or control neural plasticity may be critical in future treatments for neurologic disorders and the recovery from brain injury. In this paper, we present a protocol on the use of neurofeedback training with functional magnetic resonance imaging to modulate human brain function.

Un protocole pour l’Administration de la Real-Time IRMf formation Neurofeedback

Neurologic disorders are characterized by abnormal cellular-, molecular-, and circuit-level functions in the brain. New methods to induce and control ...

Chronic Implantation of Whole-cortical Electrocorticographic Array in the Common Marmoset

Electrocorticography (ECoG) allows the monitoring of electrical field potentials from the cerebral cortex with high spatiotemporal resolution. Recent development of thin, flexible ECoG electrodes has enabled conduction of stable recordings of large-scale cortical activity. We have developed a whole-cortical ECoG array for the common marmoset. The array continuously covers almost the entire lateral surface of cortical hemisphere, from the occipital pole to the temporal and frontal poles, and it captures whole-cortical neural activity in one shot. This protocol describes a chronic implantation procedure of the array in the epidural space of the marmoset brain. Marmosets have two advantages regarding ECoG recordings, one being the homologous organization of anatomical structures in humans and macaques, including frontal, parietal, and temporal complexes. The other advantage is that the marmoset brain is lissencephalic and contains a large number of complexes, which are more difficult to access in macaques with ECoG, that are exposed to the brain surface.These features allow direct access to most cortical areas beneath the surface of the brain. This system provides an opportunity to investigate global cortical information processing with high resolutions at a sub-millisecond order in time and millimeter order in space.

We have developed a whole-cortical electrocorticographic array for the common marmoset that continuously covers almost the entire lateral surface of cortex, from the occipital pole to the temporal and frontal poles. This protocol describes a chronic implantation procedure of the array in the epidural space of the marmoset brain.

Implantation chronique d’ensemble-corticale Electrocorticographic tableau dans l’ouistiti commun

Electrocorticography (ECoG) allows the monitoring of electrical field potentials from the cerebral cortex with high spatiotemporal resolution. Recent ...

Real-Time fMRI Brain Mapping in Animals

Dynamic fMRI responses vary largely according to the physiological conditions of animals either under anesthesia or in awake states. We developed a real-time fMRI platform to guide experimenters to monitor fMRI responses instantaneously during acquisition, which can be used to modify the physiology of animals to achieve desired hemodynamic responses in animal brains. The real-time fMRI set-up is based on a 14.1T preclinical MRI system, enabling the real-time mapping of dynamic fMRI responses in the primary forepaw somatosensory cortex (FP-S1) of anesthetized rats. Instead of a retrospective analysis to investigate confounding sources leading to the variability of fMRI signals, the real-time fMRI platform provides a more effective scheme to identify dynamic fMRI responses using customized macro-functions and a common neuroimage analysis software in the MRI system. Also, it provides immediate troubleshooting feasibility and a real-time biofeedback stimulation paradigm for brain functional studies in animals.

Animal brain functional mapping can benefit from the real-time functional magnetic resonance imaging (fMRI) experimental set-up. Using the latest software implemented in the animal MRI system, we established a real-time monitoring platform for small animal fMRI.

Cartographie cérébrale IRMf en temps réel chez les animaux

Dynamic fMRI responses vary largely according to the physiological conditions of animals either under anesthesia or in awake states. We developed a ...

Electrocorticographic Recording of Cerebral Cortex Areas Manipulated Using an Adeno-Associated Virus Targeting Cofilin in Mice

The use of electrocorticographic (ECoG) recordings in rodents is relevant to sleep research and to the study of a wide range of neurological conditions. Adeno-associated viruses (AAVs) are increasingly used to improve understanding of brain circuits and their functions. The AAV-mediated manipulation of specific cell populations and/or of precise molecular components has been tremendously useful to identify new sleep regulatory circuits/molecules and key proteins contributing to the adverse effects of sleep loss. For instance, inhibiting activity of the filamentous actin-severing protein&#160;cofilin&#160;using AAV prevents sleep deprivation-induced memory impairment. Here, a protocol is&#160;described that combines the manipulation of cofilin function in a cerebral cortex area with the recording of ECoG activity to examine whether cortical cofilin modulates the wakefulness and sleep ECoG signals. AAV injection is performed during the same surgical procedure as the implantation of ECoG and electromyographic (EMG) electrodes in adult male and female mice. Mice are anesthetized, and their heads are shaved. After skin cleaning and incision, stereotaxic coordinates of the motor cortex are determined, and the skull is pierced at this location. A cannula prefilled with an AAV expressing cofilinS3D, an inactive form of cofilin, is slowly positioned in the cortical tissue. After AAV infusion, gold-covered screws (ECoG electrodes) are screwed through the skull and cemented to the skull with gold wires inserted in the neck muscles (EMG electrodes). The animals are allowed three weeks to recover and to ensure sufficient expression of cofilinS3D. The infected area and cell type are verified using immunohistochemistry, and the ECoG is analyzed using visual identification of vigilance states and spectral analysis. In summary, this combined methodological approach allows the investigation of the precise contribution of molecular components regulating neuronal morphology and connectivity to the regulation of synchronized cerebral cortex activity during wakefulness and sleep.

This article describes a protocol for the manipulation of molecular targets in the cerebral cortex using adeno-associated viruses and for monitoring the effects of this manipulation during wakefulness and sleep using electrocorticographic recordings.

Enregistrement électrocorticographique des zones du cortex cérébral manipulées à l’aide d’un virus adéno-associé ciblant la cofiline chez la souris

The use of electrocorticographic (ECoG) recordings in rodents is relevant to sleep research and to the study of a wide range of neurological conditions. ...