Asymptotic SNR of Scalar and Vector Minimum-Variance Beamformers for Neuromagnetic Source Reconstruction

Sekihara, Kensuke; Nagarajan, Srikantan S.; Poeppel, David; Marantz, Alec

doi:10.1109/tbme.2004.827926

Cited by 181 publications

(190 citation statements)

References 13 publications

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“…Beamformer weights were normalized by their vector norm to alleviate the depth bias of MEG source reconstruction (Hillebrand et al, 2012). The participant's MRI was used to define the source space with an isotropic resolution of 6 mm and the output for each location was independently derived as a weighted sum of all MEG sensor signals using the optimal source orientation (Sekihara, Nagarajan, Poeppel, & Marantz, 2004). …”

Section: Methodsmentioning

confidence: 99%

Spatiotemporal dynamics in human visual cortex rapidly encode the emotional content of faces

Dima

Perry

Messaritaki

et al. 2018

Human Brain Mapping

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Recognizing emotion in faces is important in human interaction and survival, yet existing studies do not paint a consistent picture of the neural representation supporting this task. To address this, we collected magnetoencephalography (MEG) data while participants passively viewed happy, angry and neutral faces. Using time‐resolved decoding of sensor‐level data, we show that responses to angry faces can be discriminated from happy and neutral faces as early as 90 ms after stimulus onset and only 10 ms later than faces can be discriminated from scrambled stimuli, even in the absence of differences in evoked responses. Time‐resolved relevance patterns in source space track expression‐related information from the visual cortex (100 ms) to higher‐level temporal and frontal areas (200–500 ms). Together, our results point to a system optimised for rapid processing of emotional faces and preferentially tuned to threat, consistent with the important evolutionary role that such a system must have played in the development of human social interactions.

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Section: Methodsmentioning

confidence: 99%

Spatiotemporal dynamics in human visual cortex rapidly encode the emotional content of faces

Dima

Perry

Messaritaki

et al. 2018

Human Brain Mapping

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“…The linearly constrained minimum variance scalar beamformer spatial filter algorithm (Sekihara et al, 2004) implemented in SPM8 was used to generate maps of source activity in a 10 mm grid. Coregistration to the MNI coordinates was based on three fiducials points: nasion and left and right preauricular.…”

Section: Methodsmentioning

confidence: 99%

Hippocampal Theta-Phase Modulation of Replay Correlates with Configural-Relational Short-Term Memory Performance: Figure 1.

Poch¹,

Fuentemilla²,

Barnes³

et al. 2011

J. Neurosci.

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There is now growing evidence that the hippocampus generates theta rhythms that can phase bias fast neural oscillations in the neocortex, allowing coordination of widespread fast oscillatory populations outside limbic areas. A recent magnetoencephalographic study showed that maintenance of configural-relational scene information in a delayed match-to-sample (DMS) task was associated with replay of that information during the delay period. The periodicity of the replay was coordinated by the phase of the ongoing theta rhythm, and the degree of theta coordination during the delay period was positively correlated with DMS performance. Here, we reanalyzed these data to investigate which brain regions were involved in generating the theta oscillations that coordinated the periodic replay of configuralrelational information. We used a beamformer algorithm to produce estimates of regional theta rhythms and constructed volumetric images of the phase-locking between the local theta cycle and the instances of replay (in the 13-80 Hz band). We found that individual differences in DMS performance for configural-relational associations were related to the degree of phase coupling of instances of cortical reactivations to theta oscillations generated in the right posterior hippocampus and the right inferior frontal gyrus. This demonstrates that the timing of memory reactivations in humans is biased toward hippocampal theta phase.

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“…The average referenced EEG was bandpass-filtered between 1 and 20 Hz and non-overlapping data segments of 1 s duration were tapered with a Hanning window and Fourier transformed. Fourier coefficients were then projected to grey matter voxels with an adaptive spatial filter (scalar minimum variance beamformer) (Sekihara et al, 2004). We subsequently calculated the imaginary component of coherence (IC) between all possible voxel pairs during the entire resting-state recording for each frequency bin between 1 and 20 Hz (frequencies <1 Hz and >20 Hz were not investigated because of the larger susceptibility to artifacts and technological limitations of surface EEG to reliably reconstruct these rhythms).…”

Section: Functional Connectivity Analysismentioning

confidence: 99%

The behavioral significance of coherent resting-state oscillations after stroke

et al. 2012

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Stroke lesions induce not only loss of local neural function, but disruptions in spatially distributed areas. However, it is unknown whether they affect the synchrony of electrical oscillations in neural networks and if changes in network coherence are associated with neurological deficits. This study assessed these questions in a population of patients with subacute, unilateral, ischemic stroke.Spontaneous cortical oscillations were reconstructed from high-resolution electroencephalograms (EEG) with adaptive spatial filters. Maps of functional connectivity (FC) between brain areas were created and correlated with patient performance in motor and cognitive scores.In comparison to age-matched healthy controls, stroke patients showed a selective disruption of FC in the alpha frequency range. The spatial distribution of alpha band FC reflected the pattern of motor and cognitive deficits of the individual patient: network nodes that participate normally in the affected functions showed local decreases in FC with the rest of the brain. Interregional FC in the alpha band, but not in delta, theta, or beta frequencies, was highly correlated with motor and cognitive performance. In contrast, FC between contralesional areas and the rest of the brain was negatively associated with patient performance.Alpha oscillation synchrony at rest is a unique and specific marker of network function and linearly associated with behavioral performance. Maps of alpha synchrony computed from a single restingstate EEG recording provide a robust and convenient window into the functionality and organization of cortical networks with numerous potential applications.

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Asymptotic SNR of Scalar and Vector Minimum-Variance Beamformers for Neuromagnetic Source Reconstruction

Cited by 181 publications

References 13 publications

Spatiotemporal dynamics in human visual cortex rapidly encode the emotional content of faces

Spatiotemporal dynamics in human visual cortex rapidly encode the emotional content of faces

Hippocampal Theta-Phase Modulation of Replay Correlates with Configural-Relational Short-Term Memory Performance: Figure 1.

The behavioral significance of coherent resting-state oscillations after stroke

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