Este trabajo fue posible gracias a subvenciones apoyadas por la Oficina de Investigación del Ejército de EE.UU. (W911NF-07-1-0415 (SG), W911NF-08-1-0216 (SG)) y el (NIH / NIBIB EB006356 (GS) y EB00856 ( JRW y GS)). Los autores agradecen a Sean Austin para el módulo de SigfriedSigProcLAVA, y Griffin Milsap para la asistencia técnica relacionada.

1. Electrodo de localización <ol><li> Se recoge una pre-operatorio T1 resonancia magnética estructural (1.5T o 3T) de la cabeza del paciente: 256 x 256 píxeles por rebanada, el campo de visión completo, sin interpolación, un ancho de corte mm, preferiblemente sagital secciones. </li><li> Tenga en cuenta la implantación quirúrgica de las redes y bandas. Recoge fotografías digitales de los electrodos in situ, y las notas del neurocirujano sobre la ubicación de las redes implantadas y las tiras. </li><li> Recoge los post-operatorios de cráneo imágenes de rayos X y tomografías computarizadas del cerebro a alta resolución (1 mm de ancho de corte, piel con piel, sin ángulo). </li><li> Crear un modelo cortical tridimensional del cerebro del paciente utilizando la resonancia magnética pre-operatorio, y co-registro con la red después de la implantación de las imágenes de TC. Utilizamos el paquete de software CURRY para este propósito, y exportar la estructura cortical en 3D y un electrodo de coordenadas en el formato de MATLAB. Desde MATLAB, exportamos una película que muestra los electrodos asignados en el cerebro. También mAP el electrodo coordina con el estándar de las áreas de Brodmann utilizando un sistema automatizado de atlas de Talairach. </li><li> Revise la información del modelo en 3D, imágenes de rayos X, fotografías y notas. Finalizar un esquema de numeración para los electrodos, y el trabajo con los técnicos del hospital para asegurar que los electrodos estén conectadas a la repartidores después de esta numeración exacta. También crear un diseño esquemático para el trazado de los electrodos en dos dimensiones, de tal manera que todas las posiciones de los electrodos puede distinguirse claramente sin solapamiento. Si se va a ejecutar Sigfried (ver sección 4), salvo estas coordenadas de dos dimensiones como un fragmento de parámetros BCI2000, en el formato requerido por el parámetro ElectrodeLocations. Por último, seleccione dos ubicaciones de los electrodos que pueden ser electrocorticographically &quot;silenciosa&quot;, es decir, no están cerca de la corteza elocuente presunto, para usar como motivo inicial y de referencia (preparar los g.USBamps parcheando la referencia a las tomas de color azul, y tierraa las tomas de color amarillo, de la extrema derecha de cada unidad). </li></ol> 2. Hardware y configuración del software <ol><li> Asegúrese de que las especificaciones del ordenador son los adecuados para el manejo de los requerimientos de procesamiento del experimento. Un procesador multi-core es probable que sea necesario para dar cabida a las demandas de la adquisición en tiempo real y procesamiento de datos, grabación de vídeo, y otras tareas necesarias. Para la grabación y el análisis en tiempo real de 128 canales a 1200 Hz, se utiliza un 3 GHz quad-core con 4 GB de memoria RAM. Los amplificadores deben estar conectados a un controlador de USB dedicado, distinto del controlador (s) utilizado por otros periféricos de gran ancho de banda, tales como discos duros externos y cámaras (esto puede ser verificado a través de Administrador de dispositivos del sistema). Por último, debe haber suficiente espacio en disco para almacenar hasta 5 MB por segundo de datos experimentales, y un sistema para archivar y realizar backups. </li><li> Configurar el equipo de investigación (amplificadores, la computadora, la pantalla del experimentador, keyboard, altavoces, micrófono y cámara) en un solo carro, que puede ser rápidamente puso dentro y fuera de la habitación del paciente, con sólo un solo cable de alimentación para enchufar en la pared. Para mover el equipo desde una habitación a otra, utilice la función de hibernación antes de desenchufarla. La pantalla del paciente de vídeo debe estar en una mesa bandeja separada o en el brazo del monitor. Teniendo en cuenta que el paciente es propenso a convulsiones, asegúrese de que todos los equipos se puede rodar fuera de la manera rápida en caso de que el personal médico necesita acceso inmediato para el paciente. El equipo también debe ser desinfectada con antiséptico antes y después de su uso en la habitación del paciente. </li><li> Tiempo con el paciente es limitado, y todos los procedimientos deben ser robustos y optimizados para hacer el mejor uso de ese tiempo. En este sentido, la flexibilidad y la solidez de BCI2000 son características valiosas. Asegúrese de que los experimentos pueden ser lanzados en el toque de un botón. En el caso de BCI2000, utilice un archivo por lotes para iniciar la combinación correcta deBCI2000 módulos de forma automática, con la necesaria línea de comandos. El operador y los módulos de gUSBampSource se requieren, junto con el SignalProcessing apropiado y módulos de aplicación para su experimento en particular. Utilice la función de operador BCI2000 de secuencias de comandos para garantizar que todos los archivos de parámetros necesarios se cargan automáticamente, incluyendo los que son específicos de este paciente, tales como el número de electrodos y sus nombres y posiciones. El propósito de esta automatización es reducir al mínimo el número de pasos manuales por el experimentador, y por lo tanto las posibilidades de error. El software y los parámetros que se han finalizado y probado (tal vez con un tema EEG) por lo menos una o dos semanas antes de la implantación. También es muy recomendable realizar una &quot;seca&quot; ejecutar el día antes de la primera sesión experimental, incluyendo todos los nuevos pacientes los parámetros específicos. </li></ol> 3. Sesión montaje experimental <ol><li> Elige tu momento paralo que sugiere grabaciones experimentales para el paciente, dando cuenta de ellos al principio del día, y de nuevo 15 minutos antes de empezar. Trabaje alrededor de los visitantes, comidas, siestas, procedimientos médicos y del paciente al estado físico, emocional y cognitivo. Es importante establecer una relación con el personal médico en el suelo, para ayudar en la optimización del tiempo y la duración de las grabaciones. </li><li> Rueda el equipo en su lugar, conectarse a la toma de corriente, encienda la pantalla de vídeo del sujeto y conectarlo a la computadora, y des-hibernar el equipo. </li><li> Lanzamiento BCI2000. Con el parámetro VisualizeSource activado, pulse Set Config. El visor de la señal se abre, lo que le permite evaluar la calidad de la señal ECoG. Haga clic derecho en el visor y ajuste el filtro de paso alto a un corte de 5 Hz. (Este ajuste del filtro sólo afectará a la visualización, y no la recogida de datos.) </li><li> Compruebe si hay interferencias del ruido de la línea de alimentación: ¿La activación de un filtro de corte en el visor (a 50 Hz o 60 Hz,dependiendo de qué país se encuentra en) hacer una gran diferencia a la señal? Si es así, tratar de reducir esta mediante la eliminación de los no utilizados de la Cruz-que hablan los cables, o la identificación y eliminación de otras fuentes de interferencia de energía. Cambiar los electrodos utilizados para la referencia y el suelo si es necesario. </li><li> Si usted está usando un ojo-tracker, la calibración utilizando el software de calibración proporcionado por el fabricante. El módulo de fuente de BCI2000 debe ser compilado con la extensión EyetrackerLogger incluido, y debería ponerse en marcha con la opción - LogEyetracker = 1 flag activado, de modo que los datos de seguimiento de los ojos pueden ser adquiridos en sintonía con las señales de ECoG. </li><li> Para evitar distracciones e interrupciones, y para minimizar la interferencia de señal posible, asegúrese de que los televisores, radios y teléfonos móviles están apagados. </li><li> Dar instrucciones precisas al paciente para el experimento que se va a ejecutar. Dependiendo de la tarea del sujeto, preparado diapositivas de PowerPoint que muestran la tarea, la postura sugerida, etc, puede resultar útil. </li&gt; <li> Pulse Iniciar en el operador para iniciar el experimento. Cada vez que pulse Inicio o reanudación, un nuevo archivo será creado para evitar sobrescribir los datos anteriores, y el archivo se inicializa con una copia de todos los valores de los parámetros. Los datos brutos a continuación, se emitirá de forma automática en el archivo, junto con marcadores de eventos, hasta que se pulse de suspensión o de los acabados de ejecución de experimentación. </li><li> A lo largo de la sesión, vigilar la conducta del paciente y las señales de ECoG para las convulsiones, sospechosos, y estar listo para responder a las instrucciones del personal médico. </li></ol> 4. Ejemplo experimental de la sesión: Asignación de Sigfried clínica con BCI2000 <ol><li> Preparación: Antes de que comience la sesión, tendrá que haber preparado un archivo model.ini que contiene los parámetros de procesamiento de señales Sigfried se utilizan para construir un modelo y un archivo PRM (o por separado fragmentos de movilidad reducida.) Que contiene los parámetros que BCI2000. el módulo SigfriedSigProcva a utilizar para visualización en tiempo real. Dos parámetros fundamentales que son ElectrodeLocations, especificando el diseño en 2-D que usted ha elegido para los electrodos de particulares de este paciente, y ElectrodeCondition, que especifica que las diferentes tareas se asignarán en qué condiciones. En este ejemplo, estamos utilizando el módulo de StimulusPresentation simple para comunicar las instrucciones para el paciente, por lo que el parámetro de estímulos también debe adaptarse a las tareas que intentamos hacer funcionar. </li><li> Paso de referencia: Inicio de los módulos gUSBampSource, DummySignalProcessing y StimulusPresentationTask, configuradas para la actividad ECoG muestra de todas las redes y las tiras de 1200Hz, paso-alto-filtrada a 0,1 Hz. Instruya al sujeto para relajarse y permanecer inmóvil con los ojos abiertos. Registro 6 minutos de actividad basal, bajo la iluminación confortable en un ambiente tranquilo. </li><li> Paso de modelado: Inicie la herramienta data2model_gui y extraer características en 5 contenedores Hz from 70 a 110 Hz utilizando el método de entropía máxima para cada 500 ms de datos. Presione construir el modelo para construir un modelo probabilístico de las características espectrales seleccionados utilizando mezclas de gaussianas. </li><li> Paso Cartografía: Inicie el gUSBampSource, SigfriedSigProcLAVA y los módulos de StimulusPresentationTask y configurar el operador para cargar el modelo probabilístico, el modelo cortical, y el 2 - y 3-dimensionales coordenadas de los electrodos. Después de instruir el asunto, iniciar el proceso de asignación. En este proceso, un sujeto se realizar cada tarea durante 10 segundos a la vez, en cada uno de 5 repeticiones. Durante cada tarea, Sigfried detecta tarea relacionada con la actividad ECoG que se presenta en continua actualización 2 - y 3-mapas tridimensionales de la corteza elocuente. En los mapas de dos dimensiones, el tamaño y enrojecimiento de cada círculo representa su importancia en esta tarea en particular. Específicamente, el tamaño de cada círculo es proporcional a la fracción de la varianza total de la señal en el ba gammaª, que se contabilizará por la tarea. Esta estadística se conoce como el coeficiente de determinación, o r2. Es en el intervalo (0,1) y en la configuración actual un valor de 0,1 en general puede considerarse significativo. La ampliación de los círculos a un máximo de valores de r 2 se puede controlar mediante los controles deslizantes (ver Figura 1 C). En los mapas en 3 dimensiones, los valores de r 2 se asignan a los diferentes colores en lugar de circulares de tamaño. </li></ol> 5. Los resultados representativos La figura 1 muestra los resultados representativos, de una sesión de mapeo Sigfried en un paciente. El paciente era un hombre de 28 años de edad, diestro mujer que tenía intratable localización relacionada con la epilepsia de la izquierda-temporal inicio con generalización secundaria. 120 electrodos subdurales electrocorticográfica fueron implantados por delante del izquierdo frontal, parietal y la corteza temporal. Una radiografía lateral (panel A) y una fotografía intraoperatoria (panel B) representan elconfiguración de una rejilla frontal con 40 electrodos, una mayor densidad de rejilla temporal con 68 electrodos, y tres tiras de cada uno de 4 electrodos. A partir de los ataques registrados, un neurólogo localizado el foco epiléptico y se determinó que era necesario para llevar a cabo la resección quirúrgica del lóbulo temporal izquierdo sin dañar la corteza elocuente lenguaje. Esto se realizó con éxito: a los 8 meses después de la resección, el paciente ha sido evaluado como libres de crisis y sin déficits neurológicos. El procedimiento de asignación de pasivos Sigfried corteza identificados participan en la función del lenguaje mediante el contraste relacionadas con las tareas cambios durante las tareas de escucha. Los resultados se presentan en dos interfaces: una interfaz de 2-dimensional (panel C), lo que hace que la disposición de los electrodos claro, y una interfaz 3-dimensional anatómicamente correcto (panel D). De izquierda a derecha, el contraste paneles de escuchar el lenguaje hablado basal frente (VOZ), escuchar los tonos de línea de base frente al (tonos), y escuchar el lenguaje hablado frente a lisfondo mientras se escucha tonos (idioma). El último de éstos se incluye como una imagen aproximada de la función auditiva que es específico para el lenguaje receptivo. Los resultados de la condición VOZ mostraron una buena concordancia con los lugares en los que interrumpieron la función ECS lenguaje receptivo en este paciente (marcados como círculos de color amarillo en el panel A). <img alt="Figura 1" src="/files/ftp_upload/3993/3993fig1.jpg" /> Figura 1. Resultados del ejemplo de un paciente. El panel A muestra una radiografía lateral. Los círculos amarillos marcan los electrodos implicados en el lenguaje receptivo, tal como se determinó posteriormente mediante el mapeo estimulación electrocortical. Grupo B es una fotografía tomada durante la implantación. El panel C muestra los resultados de los mapas en un Sigfried esquemática de dos dimensiones de diseño: el tamaño y enrojecimiento de cada disco representa la importancia de la implicación de cada electrodo en la tarea, respecto al valor basal. En el panel D, la misma estadística se asigna a color en un rende el cerebro en tres dimensiones del modelorojo de resonancia magnética del paciente.

<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>

No hay conflictos de interés declarado.

La recolección de datos para la investigación ECoG requiere una estrecha colaboración entre clínicos e investigadores, con un gran equipo multidisciplinario solución de problemas en la neurología clínica, neurocirugía, neurología básica, ciencias de la computación y la ingeniería eléctrica. La recompensa es que las señales ECoG, y en las amplitudes particular en el intervalo de gamma de alta frecuencia (70-110Hz), son altamente valiosos. No sólo proporcionar información científica sobre los correlatos n...

<ol><li> 8 x 16 canales amplificadores (g.USBamp <a href="http://gtec.at" target="_blank">http://gtec.at</a> ) </li><li> 2 x 64 canales de break-out box (divisor de la cabeza de la caja) </li><li> 2 x Cable de conexión del divisor de sistema clínico </li><li> 2 x Cable de conexión del divisor de cuatro g.USBamps </li><li> 2 x cuatro direcciones adaptador de corriente para cuatro g.USBamps </li><li> 2 x cuatro direcciones del adaptador de sincronización para sincronizar cuatro g.USBamps </li><li> 1 x Cable de sincronización para sincronizar dos grupos de cuatro g.USBamps </li><li> 1 x Potencial de ecualización de pinza + cable para g.USBamp </li><li> 18 x cables de arranque Touchproof </li><li> 2 x cuatro vías USB 2.0 cubos </li><li> Regleta </li><li> Ordenador portátil o de escritorio (ver sección 2.1) </li><li> Carrito de compras, muebles de todo lo anterior </li><li> Eyetracker (u ordinaria monitor LCD) para el paciente </li><li> La bandeja móvil para el monitor de paciente </li><li> Otros periféricos (joysticks, etc) para los pacientes las respuestas conductuales </li><li> BCI2000 de software </li><li> CUrry de software </li><li> El software 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

Se presenta un método para recoger las señales de electrocorticográfica con fines de investigación de los seres humanos que están sometidos a supervisión de la epilepsia invasiva. Se muestra cómo utilizar la plataforma de software BCI2000 de recogida de datos, procesamiento de señales y la presentación del estímulo. En concreto, se demuestra Sigfried, una herramienta basada en BCI2000 de mapas en tiempo real funcional del cerebro.

Grabación electrocorticográfica Humanos (ECoG) Las señales de la investigación neurocientífica y en tiempo real el mapeo cortical funcional

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

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Research

JoVE Journal

Neuroscience

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

25.5K vistas.  New York State Department of Health. Se presenta un método para recoger las señales de electrocorticográfica con fines de investigación de los seres humanos que están sometidos a supervisión de la epilepsia invasiva. Se muestra cómo utilizar la plataforma de software BCI2000 de recogida de datos, procesamiento de señales y la presentación del estímulo. En concreto, se demuestra Sigfried, una herramienta basada en BCI2000 de mapas en tiempo real funcional del cerebro.

Video: 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.

Mapeo funcional con MEG y EEG simultáneo

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

Investigación

Neurociencias

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.

La correlación entre las respuestas de comportamiento a las señales de fMRI de la corteza prefrontal humana: estudio de determinados procesos cognitivos Uso del análisis de tareas

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.

Imagen de calcio funcionales en el desarrollo de redes corticales

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.

La implantación quirúrgica de electrodos neuronales crónicas para registrar la actividad y señales de una sola unidad electrocorticográfica

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.

Asignación Dinámica de trauma con MEG / estimaciones simultáneas norma mínima-EEG y anatómico limitado-un ejemplo: Atención Auditiva

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.

Imágenes funcionales de la corteza auditiva en los gatos adultos el uso de alto campo fMRI

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 protocolo para la administración de Real-Time fMRI entrenamiento de 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.

Implantación crónica de todo cortical matriz electrocorticográfica en el tití común

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.

Mapeo cerebral de resonancia magnética funcional en tiempo real en animales

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.

Registro electrocorticográfico de áreas de la corteza cerebral manipuladas con un virus adenoaso asociado dirigido a la cofilina en ratones

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