IEEE transactions on bio-medical engineering
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IEEE Trans Biomed Eng · Sep 2006
Maximum contrast beamformer for electromagnetic mapping of brain activity.
Beamforming technique can be applied to map the neuronal activities from magnetoencephalographic/electroencephalographic (MEG/EEG) recordings. One of the major difficulties of the scalar-type MEG/EEG beamformer is the determination of accurate dipole orientation, which is essential to an effective spatial filter. ⋯ This criterion leads to a closed-form solution of the dipole orientation. Experiments with simulation, phantom, and finger-lifting data clearly demonstrate the effectiveness, efficiency, and accuracy of the proposed method.
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IEEE Trans Biomed Eng · Sep 2006
Assessing cortical functional connectivity by partial directed coherence: simulations and application to real data.
The aim of this paper is to test a technique called partial directed coherence (PDC) and its modification (squared PDC; sPDC) for the estimation of human cortical connectivity by means of simulation study, in which both PDC and sPDC were studied by analysis of variance. The statistical analysis performed returned that both PDC and sPDC are able to estimate correctly the imposed connectivity patterns when data exhibit a signal-to-noise ratio of at least 3 and a length of at least 27 s of nonconsecutive recordings at 250 Hz of sampling rate, equivalent, more generally, to 6750 data samples.
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IEEE Trans Biomed Eng · Sep 2006
Concentration maximization and local basis expansions (LBEX) for linear inverse problems.
Linear inverse problems arise in biomedicine electroencephalography and magnetoencephalography (EEG and MEG) and geophysics. The kernels relating sensors to the unknown sources are Green's functions of some partial differential equation. ⋯ We relate the inverse problem to spatial Fourier analysis, and the resolution limits to uncertainty principles, providing conceptual links to underlying physics. Motivated by the spectral concentration problem and multitaper spectral analysis, our approach constructs local basis sets using maximally concentrated linear combinations of the measurement kernels.
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We introduce a bottom-up model for integrating electroencephalography (EEG) or magnetoencephalography (MEG) with functional magnetic resonance imaging (fMRI). An extended neural mass model is proposed based on the physiological principles of cortical minicolumns and their connections. The fMRI signal is extracted from the proposed neural mass model by introducing a relationship between the stimulus and the neural activity and using the resultant neural activity as input of the extended Balloon model. The proposed model, validated using simulations, is instrumental in evaluating the upcoming combined methods for simultaneous analysis of MEG/EEG and fMRI.
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IEEE Trans Biomed Eng · Aug 2006
Comment LetterOn the optimal defibrillation waveform--how to reconcile theory and experiment?
Medical intervention by electrical current as applied to humans or animals may have tremendous therapeutic impact if delivered while being carefully controlled. Otherwise, the situation can be harmful in terms of injury or even become lethal. ⋯ The anticipated answer is not simply a range somewhere between a maximum and a minimum, but most likely an "intelligently" selected case-specific optimum, delicately positioned between effective and unsafe. Combining insight from theory with pertinent experimental findings may offer a clearer view on an unresolved issue that often points to a cross-road of life and death.