Magnetoencephalography - a noninvasive brain imaging method with 1 ms time resolution

Gratta, Cosimo Del; Pizzella, Vittorio; Tecchio, Franca; Romani, Gian Luca

doi:10.1088/0034-4885/64/12/204

Cited by 110 publications

(66 citation statements)

References 87 publications

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“…This problem does not permit a unique solution. For this reason, it is necessary to acquire supplementary information [Del Gratta et al, 2001], i.e., to define the parameters of the forward problem, to obtain position, intensity, and direction of the modeled cerebral currents (single and multiple dipoles [Scherg and Berg, 1991], music [Mosher et al, 1992], RAP music [Mosher and Leahy, 1999], minimum norm estimates [Hämäläinen and Ilmoniemi, 1994], low-resolution brain electromagnetic tomography (LORETA) [Pascual-Marqui et al, 1995], and synthetic aperture magnetometry (SAM) [Vrba and Robinson, 2001]. Currently, no universally accepted criteria exist to define adequate model except in very specific cases.…”

Section: Introductionmentioning

confidence: 99%

Functional source separation from magnetoencephalographic signals

Barbati

Sigismondi

Zappasodi

et al. 2006

Human Brain Mapping

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We propose a novel cerebral source extraction method (functional source separation, FSS) starting from extra-cephalic magnetoencephalographic (MEG) signals in humans. It is obtained by adding a functional constraint to the cost function of a basic independent component analysis (ICA) model, defined according to the specific experiment under study, and removing the orthogonality constraint, (i.e., in a single-unit approach, skipping decorrelation of each new component from the subspace generated by the components already found). Source activity was obtained all along processing of a simple separate sensory stimulation of thumb, little finger, and median nerve. Being the sources obtained one by one in each stage applying different criteria, the a posteriori "interesting sources selection" step is avoided. The obtained solutions were in agreement with the homuncular organization in all subjects, neurophysiologically reacting properly and with negligible residual activity. On this basis, the separated sources were interpreted as satisfactorily describing highly superimposed and interconnected neural networks devoted to cortical finger representation. The proposed procedure significantly improves the quality of the extraction with respect to a standard BSS algorithm. Moreover, it is very flexible in including different functional constraints, providing a promising tool to identify neuronal networks in very general cerebral processing.

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Section: Introductionmentioning

confidence: 99%

Functional source separation from magnetoencephalographic signals

Barbati

Sigismondi

Zappasodi

et al. 2006

Human Brain Mapping

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“…(6). In this regime (q ≪ 1) circle and square loop, give identical results, so that any information about the shape of the magnetometer loop is lost.…”

Section: ) the Gray Dotted Curve Shown On The Left Has Been Obtainementioning

confidence: 76%

Sensitivity and spatial resolution of square loop SQUID magnetometers

Rombetto

Vettoliere

Granata

et al. 2008

Physica C: Superconductivity

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We calculate the flux threading the pick-up coil of a square SQUID magnetometer in the presence of a current dipole source. The result reproduces that of a circle coil magnetometer calculated by Wikswo [1] with only small differences. However it has a simpler form so that it is possible to derive from it closed form expressions for the current dipole sensitivity and the spatial resolution. The results are useful to assess the overall performance of the device and to compare different designs.

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“…Se utilizó un modelo simple de dipolo equivalente de corriente (equivalent current dipole ECD) para calcular la localización espacial de las corrientes neuronales que generan la actividad epileptógena 8,9 . La localización de los dipolos fue calculada en referencia a las coordenadas cartesianas definidas por los puntos anatómicos fuduciales (meatos externos auriculares y nasion).…”

Section: Casounclassified

Crisis del lóbulo temporal registrada mediante magnetoencefalografía: caso clínico

Amo

Santiuste

Maestú

et al. 2004

Arq. Neuro-Psiquiatr.

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RESUMEN -La localización del inicio de las crisis es un factor importante para la evaluación prequirúrgica de la epilepsia. En este trabajo se describe la localización del inicio de una crisis registrada mediante magnetoencefalografía (MEG) en un niño de 12 años que presenta crisis parciales complejas farmacorresistentes. La RM muestra una lesión de 20mm de diámetro en el hipocampo izquierdo. EEG de superficie con ondas theta temporales izquierdas. Registro MEG interictal con punta-onda aislada posterior e inferior a la lesión de la RM. Registro MEG ictal con punta-onda (2 Hz). La localización de los dipolos indica el inicio de la crisis en la circunvolución temporal inferior en la misma localización que la actividad interictal MEG. Esta actividad ictal se propaga bilateralmente a áreas frontales. El registro corticográfico intraquirúrgico confirma los resultados de la localización interictal mediante MEG.PALABRAS CLAVE: electrocorticografía, inicio ictal, magnetoencefalografía, propagación. Temporal lobe seizure recorded by magnetoencephalography: case reportABSTRACT -Ictal onset localization is a important factor in presurgical evaluation of epilepsy. This paper describes the localization of a seizure onset recorded by magnetoencephalography (MEG) from a 12-year-old male patient who suffered from complex partial drug-resistant seizures. MRI revealed a 20mm diameter lesion located in left hippocampus. Scalp EEG showed left temporal theta waves. Interictal MEG registrations detected isolated spike-wave activity posterior and inferior to the MRI lesion. Ictal MEG showed continuous spike-wave activity (2 Hz). Dipole localization sited seizure onset in the inferior left temporal gyrus, the same localization of the interictal MEG activity. This ictal activity spreads bilaterally to frontal areas. Intrasurgical electrocorticography recording confirmed interictal MEG results.KEY WORDS: electrocorticography, magnetoencephalography, seizure onset, spreading.La magnetoencefalografía (MEG) en combinación con las imágenes de resonancia magnética (RM) proporciona excelente resolución espacial (milíme-tros) y temporal (milisegundos) en el diagnóstico de la epilepsia, aumentando la capacidad de localización anatómica de la actividad en episodios clíni-cos y subclínicos 1 . La localización del foco epiléptico mediante MEG ha sido confirmada con técnicas intraquirúrgicas tal como la estimulación eléctrica cortical 2 , la electrocorticografía (ECoG) 3 y la monitorización invasiva con electrodos subdurales 4 . A pesar de que la capacidad de localización espacial se reduce por los movimientos de la cabeza durante la crisis generalizadas, bajo condiciones especiales se pueden obtener del trazado MEG datos sobre el inicio ictal 5 . Así la localización basada en datos ictales claramente definidos es considerada como superior a la basada en datos intercríticos 6 y puede aportar información equivalente o superior a la de los registros EEG invasivos 7 . En este artículo se describe la localización anatómica del inicio de una crisis parc...

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Magnetoencephalography - a noninvasive brain imaging method with 1 ms time resolution

Cited by 110 publications

References 87 publications

Functional source separation from magnetoencephalographic signals

Functional source separation from magnetoencephalographic signals

Sensitivity and spatial resolution of square loop SQUID magnetometers

Crisis del lóbulo temporal registrada mediante magnetoencefalografía: caso clínico

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