Gli autori desiderano ringraziare Matti S. Hämäläinen, Lilla Zöllei e tre revisori anonimi per i loro utili commenti. Fonti di finanziamento: R00DC010196 (AKCL); T32DC000018 (EDL); T32DC005361 (RKM).

1. Anatomica di acquisizione e trattamento <ol><li> Acquisire una magnetizzazione preparato rapida gradient echo (MPRAGE) risonanza magnetica del soggetto. Questo può richiedere 5-10 minuti a seconda del protocollo scansione specifica viene utilizzato. </li><li> Acquisire due ulteriori veloce angolo basso (FLASH) risonanza magnetica (angoli a fogli mobili = 5 ° e 30 °) se i dati EEG vengono utilizzati per l&#39;analisi di immagini inversa, come sequenze FLASH il contrasto diversi tessuti a partire dalle sequenze MPRAGE standard 1. </li><li> Utilizzare FreeSurfer software (vedi tabella) 2, 3 per ricostruire la superficie corticale e di istituire M individuale / EEG spazio di origine dipolo. <ol><li> Questo spazio sorgente è vincolata al confine sostanza grigia / bianca segmentato dalla scansione MPRAGE. Ogni emisfero contiene circa 100.000 vertici potenziali, distanziati a ~ 1 mm. Per la stima di ampiezza dipolo (vedi sotto), usare una griglia con spaziatura di 7 mm, che produce ~ 3000 dipoli per ogni emisfero. </li></ol></li><li> Ricostruirela pelle, cranio esterno e le superfici interne del cranio dalle immagini MPRAGE e FLASH con MNE (vedi tabella) e FreeSurfer. Utilizzare queste superfici per generare un modello a tre livelli elemento di contorno (BEM). </li></ol> 2. M / EEG Acquisizione Dati <ol><li> Preparare soggetto per M / EEG registrazione. <ol><li> Fare riferimento a Liu ed altri 4 per i dettagli e l&#39;elettrodo di elettrooculogramma preparazione di riferimento, nonché la digitalizzazione dei punti di riferimento fiduciali del soggetto, testa di posizione bobine indicatori (HPI) e gli elettrodi EEG. </li></ol></li><li> Una volta soggetto è seduto nella MEG, misurare la posizione della testa utilizzando le bobine HPI. </li><li> Avviare la registrazione. Inizia la presentazione di stimoli uditivi e visivi. <ol><li> Molti hardware e soluzioni software sono disponibili per eseguire presentazione dello stimolo (ad es., Presentazione, E-Prime). Usiamo un Tucker-Davis RZ6 Tecnologie per la presentazione uditiva stimolo e grilletto convalida, con Psychtoolbox 5 per visiva stimulus presentazione, entrambe controllate da MATLAB. Test delle latenze uditivi e visivi utilizzando un microfono e fotodiodo attaccato allo schermo, e, successivamente, avendo cura di evitare il jitter osservabile (che può richiedere l&#39;impostazione della presentazione proiettore la sua risoluzione nativa) prima dell&#39;esperimento aiuta a garantire l&#39;integrità dei tempi. </li></ol></li><li> Oggetto risponde a stimoli uditivi e visivi mediante un box pulsante ottico durante l&#39;esecuzione di attività comportamentale. </li><li> Salva tutti gli stimoli, i parametri sperimentali e file di dati per analisi off-line. </li></ol> 3. M / EEG Co-registrazione con RMN e di elaborazione dati <ol><li> Utilizzando il software multinazionale, caricare i dati digitalizzatore e modello ricostruito soggetto testa di risonanza magnetica. Selezionare punti di riferimento fiduciali per avviare processi di co-registrazione e procedere il ricorso alla procedura di allineamento automatico per completare la trasformazione di coordinate (Figura 2). </li><li> Per mettere in relazione la posizione di ogni dipolo nel sp di origineasso con la posizione di ogni sensore, combinare i dati registrati HPI (vedi 2.2) per calcolare una soluzione in avanti con i tre strati BEM (vedi 1.4) </li><li> Ispezionare tutti i registrati M / EEG dati e identificare i canali che hanno varianza eccezionalmente elevato o sono completamente esaurite. Impostare questi canali come canali cattivi. </li><li> Utilizzare il segnale-spazio di proiezione 6 o altre tecniche di riduzione del rumore (come la separazione del segnale spazio 7) per proiettare o separare modelli di campo spaziali origine da contaminazione ambientale campo ambientale o altri segnali indesiderati fisiologici, come quelli associati con oculari lampeggia e artefatti cardiaci (Figura 3). <ol><li> Applicare dominio del tempo rimozione manufatto (ad es., Rimuovendo epoche contenenti segnali di ampiezza anormalmente elevati dovuti alla incurvamento un canale) e nel dominio della frequenza rimozione manufatto (ad es., Band-notch filtraggio a 50 o 60 Hz frequenza di rete) per aumentare ulteriormente rapporto segnale-rumore. </li></ol></li><li> Identificare un periodo di riferimento in cui il soggetto non è stato di effettuare qualsiasi operazione (ad es., 200 ms periodo prima dell&#39;inizio di ogni prova). Generare una media di queste epoche di base per ottenere una stima del rumore (anche nota come matrice di covarianza). </li><li> Identificare le epoche di interesse (ad esempio, solo di raccogliere epoche con corrette risposte comportamentali.) E definire le condizioni per contrasti sperimentali (ad esempio, epoche associata con oggetto aver collegato la loro attenzione uditiva al hemifield opposta come originariamente cued -. Condizione di &quot;Switch&quot; - rispetto a soggetti mantenere l&#39;attenzione sul hemifield originale - condizione di &quot;Hold&quot;). Generare una risposta medio per ciascuna della condizione definita. <ol><li> Queste medie possono essere basale, corretta o meno a seconda dei parametri sperimentali (v. 8), i dati qui riportati sono di riferimento con correzione. </li></ol></li><li> Combinare la matrice di covarianza (3.5) e la soluzione calcolata in avanti (3.2) per ottenere unadistribuito corticale vincolata minima norma operatore inverso che riguarda le misure dei sensori a dipolo stime correnti nello spazio di origine. <ol><li> È possibile limitare o correggere circa l&#39;orientamento dipolo alla direzione corticale normale 9. </li></ol></li><li> Generare un &quot;film cervello&quot; della stima distribuita dipolo (cioè., La stima corrente in ciascuna posizione dipolo nello spazio sorgente in tempo) per ogni condizione sperimentale (Figura 4). <ol><li> A seconda delle caratteristiche temporali del vostro disegno sperimentale, è possibile bin i dati in tempo da una media di stime attuali utilizzano i canali non si sovrappongono finestre temporali. </li></ol></li></ol> 4. Inferenza statistica Sulla base di un comune di superficie a base di sistema di coordinate <ol><li> Morph i &quot;film del cervello&quot; per ogni soggetto su un comune (media) lo spazio corticale sulla base di una superficie a base di sistema di coordinate che si allinea in modo ottimale individuale sulcal-gymodelli ral 3. Questo ci permette di confrontare o media attività corticale in tutte le materie. (Figura 5). </li><li> Ci sono molti approcci diversi di inferenza statistica. Si metterà in evidenza tre possibili approcci qui. Approcci che non sono implementate in software può essere scritto utilizzando il software-in personalizzato nostri esempi usiamo MATLAB per eseguire la non-parametrico di clustering spazio-temporale test di permutazione. Nonostante l&#39;alta dimensionalità (Spazio x Tempo x soggetti) di questi dati, tutti questi approcci possono essere eseguite utilizzando standard moderni computer desktop in pochi secondi (ROI e 4.3 approccio) a ore (non parametrica di clustering, 4.5). </li><li> Regione d&#39;interesse (ROI) approccio <ol><li> È possibile definire la ROI anatomicamente (ad es., Definita da parcellizzazione algoritmo automatico 1) e / o funzionalmente (ad es., Registrando un compito funzionale localizzative, come un Go / No Go saccade compito di identificare il oculomotoregioni r). </li><li> Si può ulteriormente limitare l&#39;analisi a un tempo specifico di interessi che è appropriato per il paradigma sperimentale (ad es., Un periodo di tempo immediatamente prima e dopo l&#39;inizio degli stimoli sonori). È inoltre possibile utilizzare altri inferenza statistica associata con analisi delle serie temporali. </li></ol></li><li> Intero cervello Bonferroni o Falso-Discovery-Rate (FDR) correzione <ol><li> Impiegare la correzione di Bonferroni o FDR se avete bisogno di tutto il cervello, tutti i tempi di analisi. </li><li> Genera una mappa statistica in ogni sede dipolo e ogni punto di tempo utilizzando le statistiche di test, come ad esempio una t-test o entro soggetti ANOVA per i dati di circa normalmente distribuiti. Ad esempio, z-score di dinamica mappatura parametro statistico delle stime MNE per le fonti fisse dipolo 10 possono essere utilizzate se accoppiato con una correzione per le correlazioni delle stime (ad esempio il conservatore Greenhouse-Geisser correzione). </li><li> Per Bonferronicorrezione, ottenere significativi spazio-tempo dai punti di soglia ad un livello di significatività di 0,05 diviso per il numero di confronti (numero di dipoli moltiplicato per il numero di punti temporali). Per un approccio meno conservativo, utilizzare FDR p-valore di correzione 11. </li></ol></li><li> Non parametrica di clustering spazio-temporale <ol><li> Utilizzare questo metodo (sulla base di una semplice estensione di 12) per trovare le regioni di grandi dimensioni, l&#39;attivazione coerente spaziale e temporale, ma meno conservatore di correzione di Bonferroni, e meno soggetto a errori statistici di tipo I che FDR controllando per la famiglia-saggio tasso di errore . <ol><li> Poiché questo approccio usa permutazione o Monte Carlo tecniche di ricampionamento, non si basa su ipotesi di normalità dei dati, e assume solo che le etichette condizione sono intercambiabili sotto l&#39;ipotesi nulla. Anche se è computazionalmente più intensa rispetto ai precedenti due approcci, può ancora essere eseguita in ore su unasingola macchina con le moderne tecnologie hardware del computer desktop. </li></ol></li><li> Genera una mappa statistica in ogni sede dipolo e ogni punto temporale utilizzando le statistiche di test, come ad esempio una t-test. </li><li> Soglia questa mappa ad una soglia di significatività preliminare, ad esempio, p &lt;0.05. </li><li> Cluster questi punti significativi putative basato su spazio-temporale di prossimità, ad es. punti significativi all&#39;interno di 5 ms e 5 mm di distanza l&#39;uno dall&#39;altro geodetica sono messi nello stesso cluster. Nota ogni cluster risultante utilizzando ipervolume o significato totale (ad es. Somma di T-score di punti nel cluster). </li><li> Eseguire un ricampionamento standard di permutazione (o Monte Carlo ricampionamento per i più grandi insiemi di dati, ad es. Numero di soggetti N&gt; 10, per risparmiare sul calcolo) prova con una statistica massima (vedere 12 per gli esempi di test di permutazione). In breve, per un sottoinsieme casuale di soggetti (scegliendo ovunque da 0 a N soggetti), etichettare le condizioni being rispetto prima di ottenere la mappa statistica, eseguire il clustering sulla nuova mappa statistica, e di ottenere il punteggio massimo di cluster per questo rietichettatura. Eseguire questa procedura su nuovi relabelings casuali fino a 2 N permutazioni di ottenere una distribuzione della statistica massima; eseguire tutte 2 N relabelings possibili produce il test di permutazione e utilizzando un sottoinsieme casuale di meno di 2 N relabelings produce un Monte Carlo (o casuale ) test di permutazione. </li><li> Ottenere il significato di un dato cluster originale (dall&#39;etichetta originale) determinando la percentuale di tempo le massime dimensioni dei cluster fosse maggiore di quello del cluster originale, ad es. cluster che erano più grandi del 95% dei glomeruli statistici massimi può essere dichiarato significativa. <ol><li> Per una discussione approfondita sulla inferenza statistica in Imaging Source MEG distribuita, vedere 13. </li></ol></li></ol></li><li> I file di dati risultanti possono essere vi<html> sualized in molti modi, tra cui l&#39;uso in modo nativo i formati utilizzati da software multinazionale di memorizzare stime corticali spazio-temporali, vale a dire file di STC. Questi, insieme etichette che possono essere prodotti corrispondenti alle regioni significative, possono essere generati utilizzando toolboxes MNE previste MATLAB e Python. </li></ol> 5. Risultati rappresentativi La figura 6 mostra una serie di risultati rappresentativi utilizzando il paradigma comportamentale delineato in Figura 4. Utilizzando la procedura non parametrica di clustering spazio-temporale (4.5), il FEF diritto è considerato significativo quando un soggetto sta eseguendo un&#39;operazione riorientamento rispetto ad un compito standard (Figura 6 a sinistra). Utilizzando l&#39;approccio ROI (4.3), l&#39;andamento temporale della FEF destra è mostrato, con il periodo di tempo che queste due condizioni sono significativamente differenti. p_upload/4262/4262fig1.jpg &quot;/&gt; Figura 1. Workflow per generare un &quot;film cervello&quot; utilizzando corticale vincolata minimo-norm stime dipolo (cfr. figura 1 in Liu et al., 2010). <img alt="Figura 2" src="/files/ftp_upload/4262/4262fig2.jpg" /> Figura 2. Software multinazionale utilizzato per facilitare canali EEG e luoghi HPI co-registrazione su un unico soggetto MRI coordinata spazio. <img alt="Figura 3" src="/files/ftp_upload/4262/4262fig3.jpg" /> Figura 3. Dati MEG prima e dopo l&#39;utilizzo di provider di servizi condivisi per rimuovere cardiaca (evidenziata in arancione) e con gli occhi-lampeggia (evidenziato in blu-verde) manufatti e filtro passa basso per eliminare la linea-frequenza. <a href="http://www.jove.com/files/ftp_upload/4262/4262fig3large.jpg" target="_blank">Clicca qui per ingrandire la figura</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 A &quot;film di cervelli&quot; sullo spazio nativo corticale del soggetto e la tempistica della presentazione audiovisiva (con stimoli uditivi presentati a 600 ms e uno stimolo visivo presentato a -600 ms) in un paradigma sperimentale (Nota:. Sarà presentato come un film nel clip filmato finale) <img alt="Figura 5" src="/files/ftp_upload/4262/4262fig5.jpg" /> Figura 5. Confronto tra un ipotetico ROI mappati sullo spazio nativo corticale del soggetto e dopo trasformata in uno spazio comune corticale. <img alt="Figura 6" src="/files/ftp_upload/4262/4262fig6.jpg" /> Figura 6. Rappresentativa spazio-temporale cluster e time-course associata due condizioni sperimentalizioni testato.

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Nessun conflitto di interessi dichiarati.

Per stimare l&#39;attivazione dipolo sulla corteccia dalle MEG acquisite / dati EEG, dobbiamo risolvere un problema inverso, che non ha una soluzione unica stabile a meno opportuni vincoli anatomicamente e fisiologicamente sane vengono applicati. Utilizzando il vincolo anatomica acquisita per singoli soggetti che utilizzano la risonanza magnetica e adottando il minimo-norma come criterio di stima, si può arrivare ad una stima inversa corticale generatore di corrente che è d&#39;accordo con le misure dei sensori. Quest...

<table border="1"><tbody><tr><td> Nome di apparecchiature / software </td><td> Società / source </td><td></td><td></td></tr><tr><td> 306-canale Vectorview MEG sistema </td><td> Eleka-Neuromag Ltd, </td><td></td><td></td></tr><tr><td> 1.5-T Avanto MRI scanner </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> Elettrodi EEG </td><td> Prodotti cervello, Easycap GmbH </td><td></td><td></td></tr><tr><td> 3Space Fastrak sistema </td><td> Polhemus </td><td></td><td></td></tr><tr><td> Pulsante della casella di ottico (FIU-932) </td><td> Disegni attuali </td><td></td><td></td></tr></tbody></table>

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

Magneto-e di elettroencefalografia (MEG / EEG) sono tecniche di neuroimaging che forniscono una alta risoluzione temporale particolarmente adatto per studiare le reti corticali coinvolte in dinamiche compiti percettivi e cognitivi, come la partecipazione a suoni diversi in un cocktail party. Molti studi precedenti hanno impiegato dati registrati a livello solo sensore, cioè., I campi magnetici o le potenziali elettrici registrati all&#39;esterno e sul cuoio capelluto, e sono generalmente concentrato sull&#39;attività che è tempo-locked alla presentazione dello stimolo. Questo tipo di evento correlato campo / analisi potenziale è particolarmente utile quando ci sono solo un piccolo numero di distinti modelli dipolari che può essere isolato ed identificato nello spazio e nel tempo. In alternativa, utilizzando informazioni anatomiche, questi modelli campi distinti possono essere localizzati come sorgenti di corrente sulla corteccia. Tuttavia, per una risposta più sostenuta che non può essere tempo-locked ad uno specifico stimolo (ad es.,in preparazione per ascoltare una delle due cifre presentate simultaneamente vocali basati sulla funzione uditiva cued) o possono essere distribuiti su più posizioni spaziali sconosciuti a priori, l&#39;assunzione di una rete distribuita corticale non può essere adeguatamente catturati utilizzando un numero limitato di fonti di focali. Qui, si descrive un procedimento che impiega i singoli dati anatomici MRI per stabilire una relazione tra i dati del sensore e l&#39;attivazione dipolo sulla corteccia attraverso l&#39;uso di minimo-norm stime (MNE). Questo approccio di imaging inversa ci fornisce uno strumento per l&#39;analisi distribuita di origine. A titolo illustrativo, si descrivono tutte le procedure che utilizzano FreeSurfer e software multinazionale, sia liberamente disponibile. Noi riassumere le sequenze di risonanza magnetica e le fasi di analisi necessari per produrre un modello in avanti che ci permette di mettere in relazione l&#39;atteso quadro di campo causata dai dipoli distribuite sulla corteccia sulle M / EEG sensori. Next, si passerà attraverso i processi necessari che ci facilitano in denoising i dati del sensore di contaminanti ambientali e fisiologiche. Avremo quindi delineare la procedura per combinare e mappatura MEG / EEG dati del sensore sullo spazio corticale, producendo così una famiglia di serie temporale di attivazione corticale dipolo sulla superficie cerebrale (o &quot;film cerebrali&quot;) relativa a ciascuna condizione sperimentale. Infine, si metterà in evidenza alcune tecniche statistiche che ci permettono di fare inferenza scientifica in una popolazione di soggetti (ad es., Eseguire l&#39;analisi a livello di gruppo) sulla base di uno spazio comune di coordinate corticale.

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

Usiamo magneto-e di elettroencefalografia (MEG / EEG), combinata con informazioni anatomiche catturato dalla risonanza magnetica per immagini (MRI), per mappare le dinamiche della rete corticale associata con attenzione uditiva.

Mappatura Dynamics corticali tramite MEG / EEG simultanee e anatomica vincolata minima norma-Stime: un esempio Attenzione Auditory

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

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JoVE Journal

Neuroscience

14.5K Views.  University of Washington. Usiamo magneto-e di elettroencefalografia (MEG / EEG), combinata con informazioni anatomiche catturato dalla risonanza magnetica per immagini (MRI), per mappare le dinamiche della rete corticale associata con attenzione uditiva.

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.

Mappatura funzionale con EEG e MEG simultaneo

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

Ricerca

Neuroscienze

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.

La preparazione e la cultura di fette di pollo uditive tronco

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.

Registrazione umani Electrocorticographic (ECOG) Segnali per la ricerca neuroscientifica e in tempo reale la mappatura funzionale corticale

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.

Registrazioni simultanee a cellule di fotorecettori e dei neuroni di secondo ordine in un anfibio Retinal Fetta Preparazione

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.

Imaging funzionale di Auditory Cortex in gatti adulti utilizzando ad 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.

Stimolazione optogenetic del nervo uditivo

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

Touchscreen Sustained Attention Task (SAT) for Rats

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

Touchscreen Sustained Attention Task SAT for Rats

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

Touchscreen sostenuta attenzione Task (SAT) per ratti

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.

Registrazioni simultanee di potenziali di campo locale corticale, elettrocardiogramma, elettromiogramma e respirazione ritmo da un ratto liberamente commovente

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.

Modello di ratto di demielinizzazione corticale cerebrale diffusa indotta da un'iniezione intracerebrale di citochine pro-infiammatorie

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.

Modellazione statistica della connettività corticale mediante elettroencefalogrammi non invasivi

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