Comparison of the spatial resolution of source imaging techniques in high-density EEG and MEG

Hedrich, Tanguy; Pellegrino, Giovanni; Kobayashi, Eliane; Lina, Jean‐Marc; Grova, Christophe

doi:10.1016/j.neuroimage.2017.06.022

Cited by 127 publications

(145 citation statements)

References 52 publications

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“…Therefore, we recommend subsampling only one modality while keeping a dense sampling of the other modality. We recently demonstrated similar level of spatial accuracy obtained with MEM using either MEG or high‐density EEG (256 electrodes) during electrical median nerve stimulation (Hedrich et al, ). A comparison of the fusion between high‐density EEG and several subsampled MEG setups would be of interest but was out of the scope of this study.…”

Section: Discussionmentioning

confidence: 61%

“…Second, the number of MEG sensors (whole head coverage) used in relative to EEG (10–20 or 10‐10 system) is typically greater (Klamer et al, ; Ossenblok et al, ). However, it has been demonstrated that improvement in EEG localization accuracy can be attained when using high‐density electrodes and realistic geometry head models (Birot et al, ; Chowdhury et al, ; Hedrich, Pellegrino, Kobayashi, Lina, & Grova, ; Klamer et al, ; Lantz & Grave de Peralta, ; Liu, Dale, & Belliveau, ; Ryynanen, Hyttinen, & Malmivuo, ; Song et al, ; Wang et al, ). It has been shown that simultaneously acquired EEG and MEG data are super additive, that is, when combined they provide more information relevant to source localization than the sum of monomodal information (Pflieger, Simpson, Ahlfors, & Ilmoniemi, ).…”

Section: Introductionmentioning

confidence: 99%

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Reproducibility ofEEG‐MEGfusion source analysis of interictal spikes: Relevance in presurgical evaluation of epilepsy

Chowdhury

Pellegrino

Aydın

et al. 2017

Human Brain Mapping

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Fusion of electroencephalography (EEG) and magnetoencephalography (MEG) data using maximum entropy on the mean method (MEM-fusion) takes advantage of the complementarities between EEG and MEG to improve localization accuracy. Simulation studies demonstrated MEM-fusion to be robust especially in noisy conditions such as single spike source localizations (SSSL). Our objective was to assess the reliability of SSSL using MEM-fusion on clinical data. We proposed to cluster SSSL results to find the most reliable and consistent source map from the reconstructed sources, the so-called consensus map. Thirty-four types of interictal epileptic discharges (IEDs) were analyzed from 26 patients with well-defined epileptogenic focus. SSSLs were performed on EEG, MEG, and fusion data and consensus maps were estimated using hierarchical clustering. Qualitative (spike-to-spike reproducibility rate, SSR) and quantitative (localization error and spatial dispersion) assessments were performed using the epileptogenic focus as clinical reference. Fusion SSSL provided significantly better results than EEG or MEG alone. Fusion found at least one cluster concordant with the clinical reference in all cases. This concordant cluster was always the one involving the highest number of spikes. Fusion yielded highest reproducibility (SSR EEG = 55%, MEG = 71%, fusion = 90%) and lowest localization error. Also, using only few channels from either modality (21EEG + 272MEG or 54EEG + 25MEG) was sufficient to reach accurate fusion. MEM-fusion with consensus map approach provides an objective way of finding the most reliable and concordant generators of IEDs. We, therefore, suggest the pertinence of SSSL using MEM-fusion as a valuable clinical tool for presurgical evaluation of epilepsy.

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Section: Discussionmentioning

confidence: 61%

Section: Introductionmentioning

confidence: 99%

Reproducibility ofEEG‐MEGfusion source analysis of interictal spikes: Relevance in presurgical evaluation of epilepsy

Chowdhury

Pellegrino

Aydın

et al. 2017

Human Brain Mapping

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“…For MEG, spikes‐on‐ripples performed better than spikes‐alone (accuracy: 82% vs. 67%), despite the fact that the association between resection and outcome did not reach significance. This result should be attributable to the low sensitivity of MEG to ripples and thus to spikes‐on‐ripple, rather than to a higher localization error, given the similar spatial resolution of HD‐EEG and MEG …”

Section: Discussionmentioning

confidence: 99%

Scalp ripples as prognostic biomarkers of epileptogenicity in pediatric surgery

Tamilia

Dirodi

Alhilani

et al. 2020

Ann Clin Transl Neurol

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Objective To assess the ability of high‐density Electroencephalography (HD‐EEG) and magnetoencephalography (MEG) to localize interictal ripples, distinguish between ripples co‐occurring with spikes (ripples‐on‐spike) and independent from spikes (ripples‐alone), and evaluate their localizing value as biomarkers of epileptogenicity in children with medically refractory epilepsy. Methods We retrospectively studied 20 children who underwent epilepsy surgery. We identified ripples on HD‐EEG and MEG data, localized their generators, and compared them with intracranial EEG (icEEG) ripples. When ripples and spikes co‐occurred, we performed source imaging distinctly on the data above 80 Hz (to localize ripples) and below 70 Hz (to localize spikes). We assessed whether missed resection of ripple sources predicted poor outcome, separately for ripples‐on‐spikes and ripples‐alone. Similarly, predictive value of spikes was calculated. Results We observed scalp ripples in 16 patients (10 good outcome). Ripple sources were highly concordant to the icEEG ripples (HD‐EEG concordance: 79%; MEG: 83%). When ripples and spikes co‐occurred, their sources were spatially distinct in 83‐84% of the cases. Removing the sources of ripples‐on‐spikes predicted good outcome with 90% accuracy for HD‐EEG (P = 0.008) and 86% for MEG (P = 0.044). Conversely, removing ripples‐alone did not predict outcome. Resection of spike sources (generated at the same time as ripples) predicted good outcome for HD‐EEG (P = 0.036; accuracy = 87%), while did not reach significance for MEG (P = 0.1; accuracy = 80%). Interpretation HD‐EEG and MEG localize interictal ripples with high precision in children with refractory epilepsy. Scalp ripples‐on‐spikes are prognostic, noninvasive biomarkers of epileptogenicity, since removing their cortical generators predicts good outcome. Conversely, scalp ripples‐alone are most likely generated by non‐epileptogenic areas.

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“…To this purpose, we took advantage of MEG. This technique allows measuring cortical activity noninvasively, with high temporal resolution, with better spatial resolution than EEG (Chowdhury et al, ; Hedrich, Pellegrino, Kobayashi, Lina, & Grova, ; Larsen et al, ; Pellegrino et al, ; Pellegrino, Tomasevic, Herz, Larsen, & Siebner, ; von Ellenrieder et al, ). This technique is also especially suitable in the context of off‐line tDCS as it does not require the application of electrodes on the scalp and has no impact on tDCS montage (Pellegrino et al, ).…”

Section: Discussionmentioning

confidence: 99%

Transcranial direct current stimulation over the sensory‐motor regions inhibits gamma synchrony

Pellegrino

Arcara

Pino

et al. 2019

Human Brain Mapping

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Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique able to induce plasticity phenomena. Although tDCS application has been spreading over a variety of neuroscience domains, the mechanisms by which the stimulation acts are largely unknown. We investigated tDCS effects on cortical gamma synchrony, which is a crucial player in cortical function. We performed a randomized, sham‐controlled, double‐blind study on healthy subjects, combining tDCS and magnetoencephalography. By driving brain activity via 40 Hz auditory stimulation during magnetoencephalography, we experimentally tuned cortical gamma synchrony and measured it before and after bilateral tDCS of the primary sensory‐motor hand regions (anode left, cathode right). We demonstrated that the stimulation induces a remarkable decrease of gamma synchrony (13 out of 15 subjects), as measured by gamma phase at 40 Hz. tDCS has strong remote effects, as the cortical region mostly affected was located far away from the stimulation site and covered a large area of the right centro‐temporal cortex. No significant differences between stimulations were found for baseline gamma synchrony, as well as early transient auditory responses. This suggests a specific tDCS effect on externally driven gamma synchronization. This study sheds new light on the effect of tDCS on cortical function showing that the net effect of the stimulation on cortical gamma synchronization is an inhibition.

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Comparison of the spatial resolution of source imaging techniques in high-density EEG and MEG

Cited by 127 publications

References 52 publications

Reproducibility ofEEG‐MEGfusion source analysis of interictal spikes: Relevance in presurgical evaluation of epilepsy

Reproducibility ofEEG‐MEGfusion source analysis of interictal spikes: Relevance in presurgical evaluation of epilepsy

Scalp ripples as prognostic biomarkers of epileptogenicity in pediatric surgery

Transcranial direct current stimulation over the sensory‐motor regions inhibits gamma synchrony

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