Los autores desean agradecer a Matti S. Hämäläinen, Zöllei Lilla y tres revisores anónimos por sus útiles comentarios. Fuentes de financiación: R00DC010196 (AKCL); T32DC000018 (EDL); T32DC005361 (RKM).

1. Adquisición de Datos y Procesamiento de Anatomía <ol><li> Adquirir una magnetización preparado rápido eco de gradiente (MPRAGE) IRM del tema. Esto puede tomar 5-10 minutos según el protocolo de exploración específica se utiliza. </li><li> Adquirir dos adicional rápido de bajo ángulo de disparo (FLASH) imágenes por resonancia magnética (ángulos flip = 5 ° y 30 °) si los datos de EEG se utiliza para el análisis de imagen inversa, como secuencias FLASH proporcionar contraste de tejidos diferentes de las secuencias MPRAGE estándar 1. </li><li> Utilice FreeSurfer software (véase el cuadro) 2, 3 para reconstruir la superficie cortical y establecer individuo M / espacio EEG fuente dipolar. <ol><li> Este espacio de origen está limitado por el límite de la materia gris / blanca segmentada de la exploración MPRAGE. Cada hemisferio contiene aproximadamente 100.000 vértices posibles, espaciados a aproximadamente 1 mm. Para la estimación de la amplitud de dipolo (ver más abajo), utilizar un espaciado de malla de 7 mm, lo que da ~ 3.000 dipolos por hemisferio. </li></ol></li><li> Reconstruirla piel, el cráneo exterior y las superficies internas del cráneo de las imágenes MPRAGE y FLASH utilizando MNE (véase el cuadro) y FreeSurfer. Usar estas superficies para generar un modelo de tres capas límite elemento (BEM). </li></ol> 2. M / EEG de Adquisición de Datos <ol><li> Preparar tema para M / EEG de grabación. <ol><li> Consulte Liu et al 4 para los detalles de electrooculograma y preparación electrodo de referencia, así como la digitalización de las señales fiduciales del sujeto, la posición de cabeza bobinas indicadoras (HPI) y electrodos de EEG. </li></ol></li><li> Una vez sujeto está sentado en el MEG, medir la posición de la cabeza usando las bobinas HPI. </li><li> Inicie la grabación. Comienza la presentación de estímulos auditivos y visuales. <ol><li> Muchos hardware y soluciones de software están disponibles para llevar a cabo la presentación del estímulo (p. ej., Presentación, E-Prime). Usamos un Tucker-Davis Tecnologías RZ6 para la presentación auditiva y estímulo desencadenante estampado, con Psychtoolbox 5 para visual spresentación timulus, ambas controladas por MATLAB. Prueba de las latencias auditivas y visuales utilizando un micrófono y un fotodiodo conectado a la pantalla, y, posteriormente, asegurar que no hay fluctuación observable (lo que puede requerir ajustar la presentación proyector a su resolución nativa) antes del experimento ayuda a garantizar la integridad de temporización. </li></ol></li><li> Asunto responde a estímulos auditivos y visuales a través de una caja de botones óptico en el desempeño de la tarea conductual. </li><li> Guarde todos los estímulos experimentales, parámetros y archivos de datos para el análisis fuera de línea. </li></ol> 3. M / Co-registro EEG con resonancia magnética y Procesamiento de Datos <ol><li> Utilizando el software de las EMN, cargar datos digitalizador y sujeto modelo reconstruido cabeza MRI. Elige hitos fiduciales para iniciar el proceso de co-registro y proceder a utilizar el procedimiento de alineación automática para completar la transformación de coordenadas (Figura 2). </li><li> Para relacionar la ubicación de cada dipolo en el sp fuenteas con la ubicación de cada sensor, se combinan los datos registrados HPI (ver 2,2) para calcular una solución hacia adelante con el BEM de tres capas (ver 1,4) </li><li> Inspeccione todas las registradas M / EEG datos e identificar los canales que tienen varianza excepcionalmente alta o están completamente plana. Ajuste estos canales como canales malos. </li><li> El uso de señales espacio de proyección 6 u otras técnicas de reducción de ruido (tales como separación de la señal espacio 7) para proyectar o separar los patrones espaciales de campo se originó de la contaminación ambiental campo ambiental u otras señales fisiológicas indeseables, tales como aquellos asociados con el ojo-parpadea y artefactos cardiacos (Figura 3). <ol><li> Aplicar el dominio del tiempo eliminación de artefactos (por ejemplo., La eliminación de épocas que contienen señales de amplitud anormalmente elevados debido a la adición de un canal) y el dominio de frecuencia eliminación de artefactos (por ejemplo., Banda-muesca filtrado a 50 o 60 Hz de frecuencia de línea) para aumentar aún más señal-a-ruido. </li></ol></li><li> Identificar un período de línea de base en el que el sujeto no se realiza cualquier tarea (por ejemplo., 200 período ms antes del inicio de cada ensayo). Generar un promedio de estas épocas de línea de base con el fin de obtener una estimación de ruido (también conocida como la matriz de covarianza). </li><li> Identificar las épocas de interés (por ejemplo, sólo recoger las épocas correctas con las respuestas de comportamiento.) Y definir las condiciones para contrastes experimentales (por ejemplo, épocas asociado con sujetos que han cambiado su atención auditiva al hemicampo opuesto originalmente con claves -. &quot;Switch&quot; condición - en comparación con sujetos mantener la atención en el hemicampo original - &quot;Hold&quot; condición). Generar un medio de respuesta para cada uno de la condición definida. <ol><li> Estos promedios se pueden basal-corregido o no dependiendo de los parámetros experimentales (ver 8); datos mostrados aquí son de línea de base corregidas. </li></ol></li><li> Combinar la matriz de covarianza (3,5) y la solución calculada hacia delante (3,2) para obtener unadistribuidos cortical constreñido mínima norma de operador inverso que relaciona las mediciones del sensor a las estimaciones actuales dipolo en el espacio de origen. <ol><li> Usted puede restringir o aproximadamente fijar la orientación del dipolo a la dirección cortical normal 9. </li></ol></li><li> Generar una &quot;película cerebro&quot; de la estimación distribuida dipolo (es decir., La estimación actual en cada ubicación de dipolo en el espacio de origen en el tiempo) para cada condición experimental (Figura 4). <ol><li> Dependiendo de las características temporales de su diseño experimental, bin pueden sus datos en tiempo al promediar las estimaciones actuales utilizando no se solapan ventanas temporales. </li></ol></li></ol> 4. Inferencia estadística basada en un sistema de coordenadas común basada en la superficie <ol><li> Morph las películas &quot;cerebro&quot; de cada sujeto sobre una común (promedio) de espacio cortical basada en un sistema de coordenadas basada en la superficie que se alinea óptimamente individuo sulcal-gyral patrones 3. Esto nos permite comparar o media actividad cortical en todas las asignaturas. (Figura 5). </li><li> Hay muchos enfoques diferentes de inferencia estadística. Destacaremos tres enfoques posibles aquí. Situaciones que no se implementan en el paquete de software puede ser escrito usando software personalizado en nuestros ejemplos utilizan MATLAB para realizar la prueba no paramétrica espacio-temporal agrupación prueba de permutación. A pesar de la alta dimensionalidad (Espacio x Tiempo x Los sujetos) de estos datos, todos estos enfoques se puede realizar utilizando el hardware estándar moderna computadora de escritorio en cuestión de segundos (ROI; 4.3 Enfoque) a horas (clustering no paramétrico; 4,5). </li><li> Región de interés (ROI) Enfoque <ol><li> Se puede definir la ROI anatómicamente (p. ej., Definido por el algoritmo de parcelación automática 1) y / o funcionalmente (p. ej., Mediante el registro de una tarea de localizadora funcional, tal como un Go / No Go tarea saccade para identificar el oculomotor regiones). </li><li> Además, usted puede limitar el análisis a un tiempo específico de interés que se adecue a su paradigma experimental (p. ej., Un período de tiempo inmediatamente antes y después de la aparición de los estímulos sonoros). También puede utilizar otra inferencia estadística asociada con el análisis de series de tiempo. </li></ol></li><li> Todo el cerebro Bonferroni o Falso-Discovery-Rate (FDR) corrección <ol><li> Emplear la corrección de Bonferroni o FDR si requiere de todo el cerebro, todo en tiempo de análisis. </li><li> Generar un mapa estadístico en cada lugar dipolo y cada punto de tiempo utilizando las estadísticas de las pruebas pertinentes, tales como un t-test o ANOVA intra-sujetos para los datos de aproximadamente normalmente distribuidos. Por ejemplo, las puntuaciones z de la asignación dinámica de parámetros estadística de las estimaciones de las EMN fijos fuentes de dipolo 10 se puede utilizar cuando se combina con una corrección para correlaciones en las estimaciones (por ejemplo, el conservador Greenhouse-Geisser corrección). </li><li> Para Bonferronicorrección, obtener importantes puntos de espacio-tiempo por umbralización a un nivel de significación de 0,05 dividido por el número de comparaciones (número de dipolos multiplicado por el número de puntos de tiempo). Para un enfoque menos conservador, utilice FDR p-valor de corrección 11. </li></ol></li><li> No paramétrico de agrupamiento espacio-temporal <ol><li> Utilizar este método (basado en una simple extensión de 12) para encontrar regiones de activación grande, consistente espacial y temporal, pero menos conservadoras que la corrección de Bonferroni, y menos propenso a errores de tipo I estadísticos que FDR mediante el control de la tasa de error de la familia sabia . <ol><li> Debido a que este método utiliza permutación o técnicas de Monte Carlo remuestreo, que no se basa en la hipótesis de normalidad de los datos, y sólo supone que las etiquetas son intercambiables condición bajo la hipótesis nula. Aunque es más computacionalmente intensivas de los dos enfoques anteriores, todavía se puede realizar en una hora ensola máquina con hardware moderno ordenador de sobremesa. </li></ol></li><li> Generar un mapa estadístico en cada ubicación de dipolo y cada punto de tiempo utilizando las pruebas estadísticas apropiadas, tales como una prueba de la t. </li><li> Umbral este mapa en un umbral de significación preliminar, por ejemplo, p &lt;0,05. </li><li> Cluster estos puntos supuestos significativos basados ​​en la proximidad espacio-temporal, por ejemplo. puntos importantes dentro de 5 ms y 5 mm de distancia geodésica entre sí, se pone en la misma categoría. Puntuación de cada grupo resultante usando hipervolumen o significado total (p. ej. Suma de las puntuaciones t de puntos en el grupo). </li><li> Realice un nuevo muestreo estándar permutación (o Monte Carlo remuestreo para grandes conjuntos de datos, por ejemplo. Número de sujetos N&gt; 10, para ahorrar en el cálculo) prueba con una estadística máxima (ver 12 para ejemplos de prueba de permutación). En pocas palabras, para un subconjunto aleatorio de los sujetos (elegir desde 0 hasta N sujetos), reetiquetar las condiciones being comparación antes de obtener el mapa estadístico, lleve a cabo la agrupación en el mapa estadística nueva, y obtener la puntuación máxima para ese grupo reetiquetado. Realizar este procedimiento en nuevos relabelings aleatorios para hasta 2 N permutaciones para obtener una distribución de la estadística máxima; realizar todo 2 N relabelings posibles produce la permutación de prueba y la utilización de un subconjunto aleatorio de menos de 2 N relabelings produce un Monte Carlo (o al azar ) prueba de permutación. </li><li> Obtener el significado de un grupo determinado original (del etiquetado original) mediante la determinación de la proporción de tiempo que los tamaños de clúster máximos fueron mayores que la de la agrupación original, por ejemplo. grupos que eran más grandes que 95% de los racimos Estadística de máximo puede ser declarado significativo. <ol><li> Para una discusión a fondo sobre la inferencia estadística en imágenes MEG fuente distribuida, ver 13. </li></ol></li></ol></li><li> Los archivos de datos resultantes pueden ser vi<html> sualized de muchas maneras, incluyendo el uso de forma nativa los formatos utilizados por las EMN software para almacenar espacio-temporales estimaciones corticales, es decir, los archivos de STC. Estos, junto a etiquetas que pueden ser producidos correspondientes a las regiones importantes, se pueden generar utilizando cajas de herramientas EMN previstas MATLAB y Python. </li></ol> 5. Los resultados representativos La figura 6 muestra un conjunto de resultados representativos utilizando el paradigma de comportamiento descrito en la Figura 4. Utilizando el procedimiento no paramétrico de clusters espaciotemporal (4,5), el FEF derecho se encuentra para ser significativo cuando un sujeto está realizando una tarea reorientación en comparación con una tarea estándar (Figura 6 a la izquierda). Utilizando el enfoque de ROI (4,3), el curso temporal de la FEF derecha se muestra, junto con el período de tiempo que estas dos condiciones son significativamente diferentes. p_upload/4262/4262fig1.jpg &quot;/&gt; Figura 1. Flujo de trabajo para la generación de una &quot;película cerebro&quot; utilizando cortical constreñido-norma mínimo estimaciones dipolo (véase la Figura 1 en Liu et al., 2010). <img alt="Figura 2" src="/files/ftp_upload/4262/4262fig2.jpg" /> Figura 2. MNE software utilizado para facilitar canales de EEG y lugares HPI co-registro en una MRI sujeto coordenadas espacio. <img alt="Figura 3" src="/files/ftp_upload/4262/4262fig3.jpg" /> Figura 3. MEG datos antes y después de usar SSP para eliminar cardíaco (resaltada en naranja) y los ojos parpadea (resaltado en azul-verde) los artefactos y filtrado de paso bajo para eliminar la línea de frecuencia. <a href="http://www.jove.com/files/ftp_upload/4262/4262fig3large.jpg" target="_blank">Haga clic aquí para ampliar la cifra</a> . <pclass = &quot;jove_content&quot; fo: keep-together.within-page = &quot;always&quot;&gt; <img alt="Figura 4" src="/files/ftp_upload/4262/4262fig4.jpg" /> Figura 4 Una &quot;película cerebro&quot; en el espacio nativo cortical del sujeto y el momento de la presentación audiovisual (con estímulos auditivos presentados en 600 ms y un estímulo visual presentada en -600 ms) en un paradigma experimental (Nota:. Este será presenta como una película en el clip de película final) <img alt="Figura 5" src="/files/ftp_upload/4262/4262fig5.jpg" /> Figura 5. Comparación entre un ROI hipotético asignado en el espacio nativo cortical de un sujeto y después se transformó en un espacio común cortical. <img alt="La figura 6" src="/files/ftp_upload/4262/4262fig6.jpg" /> Figura 6. Representante espacio-temporal del clúster y tiempo de evolución, asociada con la condición experimental dosciones probado.

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No hay conflictos de interés declarado.

Con el fin de estimar la activación de dipolo en la corteza de los MEG adquiridos / datos de EEG, que necesitamos para resolver un problema inverso, el cual no tiene una solución única estable a menos apropiados anatómica y fisiológicamente limitaciones de sonido se aplican. Utilizando la restricción anatómica adquirida por los sujetos individuales utilizando la RM y la adopción de la norma mínima como criterio de estimación, podemos llegar a una estimación inversa cortical fuente de corriente que esté de ac...

<table border="1"><tbody><tr><td> Nombre de equipo / software </td><td> Empresa / fuente </td><td></td><td></td></tr><tr><td> 306-canal Vectorview MEG sistema </td><td> Eleka-Neuromag Ltd, </td><td></td><td></td></tr><tr><td> 1,5-T Avanto escáner MRI </td><td> Siemens Medical Solutions </td><td></td><td></td></tr><tr><td> FreeSurfer </td><td></td><td></td><td> <a href="http://freesurfer.net/" target="_blank">http://freesurfer.net/</a> </td></tr><tr><td> MNE software </td><td></td><td></td><td> <a href="http://www.nmr.mgh.harvard.edu/martinos/userInfo/data/sofMNE.php" target="_blank">http://www.nmr.mgh.harvard.edu/martinos/userInfo/data/sofMNE.php</a> </td></tr><tr><td> Electrodos de EEG </td><td> Productos del cerebro, Easycap GmbH </td><td></td><td></td></tr><tr><td> 3Space Fastrak sistema </td><td> Polhemus </td><td></td><td></td></tr><tr><td> Caja de botones Óptico (FIU-932) </td><td> Diseños actuales </td><td></td><td></td></tr></tbody></table>

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

Magneto y electroencefalografía (MEG / EEG) son técnicas de neuroimagen que proporcionan una alta resolución temporal especialmente adecuado para investigar las redes corticales implicadas en tareas dinámicas perceptivas y cognitivas, tales como asistir a diferentes sonidos en un cóctel. Muchos estudios anteriores han utilizado los datos registrados en el sensor de nivel único, es decir., Los campos magnéticos o los potenciales eléctricos registrados fuera y en el cuero cabelludo, y por lo general han centrado en la actividad que lleva mucho tiempo bloqueado a la presentación del estímulo. Este tipo de evento relacionado con campo / análisis de potencial es particularmente útil cuando sólo hay un pequeño número de distintos patrones dipolares que pueden ser aislados e identificados en el espacio y el tiempo. Alternativamente, mediante la utilización de la información anatómica, estos patrones de campo distintos pueden ser localizados como fuentes de corriente sobre la corteza. Sin embargo, para una respuesta más sostenida que no puede ser tiempo-bloqueado a un estímulo específico (p. ej.,en preparación para escuchar a uno de los dos presentados simultáneamente dígitos hablados basado en la función auditiva Complementada) o puede ser distribuido a través de múltiples localizaciones espaciales desconocidos a priori, el reclutamiento de una red cortical distribuida puede no estar adecuadamente capturado mediante el uso de un número limitado de fuentes focales. A continuación, describimos un procedimiento que emplea datos de resonancia magnética anatómicas individuales para establecer una relación entre la información del sensor y la activación de dipolo en la corteza a través del uso de estimaciones de norma mínima-(MNE). Este enfoque de imagen inversa nos proporciona una herramienta para el análisis de fuentes distribuidas. Para fines ilustrativos, se describen todos los procedimientos que utilizan FreeSurfer y software MNE, tanto libremente disponible. Vamos a resumir las secuencias de resonancia magnética y análisis de los pasos necesarios para obtener un modelo de avance que nos permite relacionar el patrón de campo previstas a causa de los dipolos distribuidos en la corteza en los sensores M / EEG. Next, vamos a pasar por los procesos necesarios que nos faciliten la eliminación de ruido en los datos del sensor de contaminantes ambientales y fisiológicos. A continuación, se describen el procedimiento para combinar y mapeo de MEG / EEG de datos del sensor en el espacio cortical, produciendo de ese modo una familia de series de tiempo de activación cortical dipolo sobre la superficie del cerebro (o &quot;películas cerebrales&quot;) en relación con cada condición experimental. Por último, destacaremos algunas técnicas estadísticas que nos permitan hacer inferencia científica a través de una población de sujetos (es decir., Lleve a cabo a nivel de grupo de análisis) sobre la base de un espacio de coordenadas cortical común.

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

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

Usamos magneto-y electroencefalografía (MEG / EEG), combinada con la información anatómica capturado por resonancia magnética (MRI), para asignar la dinámica de la red cortical asociada con la atención auditiva.

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 ...

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

Research

JoVE Journal

Neuroscience

14.5K vistas.  University of Washington. Usamos magneto-y electroencefalografía (MEG / EEG), combinada con la información anatómica capturado por resonancia magnética (MRI), para asignar la dinámica de la red cortical asociada con la atención auditiva.

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

Functional Mapping with Simultaneous MEG and EEG

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

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

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

Preparation and Culture of Chicken Auditory Brainstem Slices

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

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

Preparación y Cultura de rebanadas de pollo tronco cerebral auditivo

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

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

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

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

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

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), ...

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

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

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

Simultáneas registros de células de fotorreceptores y las neuronas de segundo orden en una rebanada preparación retina Anfibios

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

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

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

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

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 ...

Optogenetic Stimulation of the Auditory Nerve

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

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

Estimulación Optogenética del nervio auditivo

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

Touchscreen Sustained Attention Task (SAT) for Rats

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

Touchscreen Sustained Attention Task SAT for Rats

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

Pantalla táctil sostenida tarea de atención (SAT) para las ratas

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

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

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

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

Grabaciones simultáneas de potenciales de campo Local Cortical, Electrocardiograma, electromiograma y respirar a ritmo de una rata libremente móvil

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

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

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

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

Modelo de rata de desmielinización cortical cerebral generalizada inducida por una inyección intracerebral de citoquinas proinflamatorias

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

Statistical Modelling of Cortical Connectivity Using Non-invasive Electroencephalograms

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

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

Modelado estadístico de la conectividad cortical mediante electroencefalogramas no invasivos

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