Mapping the signal‐to‐noise‐ratios of cortical sources in magnetoencephalography and electroencephalography

Goldenholz, Daniel M.; Ahlfors, Seppo P.; Hämäläinen, Matti S.; Sharon, Dahlia; Ishitobi, Mamiko; Vaina, Lucia M.; Stufflebeam, Steven M.

doi:10.1002/hbm.20571

Cited by 234 publications

(221 citation statements)

References 51 publications

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“…Based on our observation, the superior temporal gyrus might be a site where MEG provides higher sensitivity for epileptic activity than EEG. This observation is in accordance with recently published computational estimates, which suggest a higher signal-to-noise ratio in MEG compared to EEG for sources in the superior temporal gyrus (among other areas) [13].…”

Section: Discussionsupporting

confidence: 92%

Voices behind the left shoulder: Two patients with right-sided temporal lobe epilepsy

Hug

Bartsch

Gutschalk

2011

Journal of the Neurological Sciences

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Section: Discussionsupporting

confidence: 92%

Voices behind the left shoulder: Two patients with right-sided temporal lobe epilepsy

Hug

Bartsch

Gutschalk

2011

Journal of the Neurological Sciences

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“…In addition, localization accuracy in the temporal lobe may be limited because a) the poor signal-to-noise ratio of very deep, mesial sources may present a suboptimal MEG signal and b) although MEG sensor arrays are designed to cover the entire head, they provide less coverage of the inferior aspect of the brain. Goldenholz et al 2 have mapped brain areas in terms of MEG sensitivity. At any rate, our results here suggest that in patients with preoperative MEG studies that show clusters in surgically accessible areas outside the temporal lobe, aggressive resection may improve the chances for seizure freedom.…”

Section: Discussionmentioning

confidence: 99%

Correlation between magnetoencephalography-based “clusterectomy” and postoperative seizure freedom

Vadera¹,

Jehi

Burgess

et al. 2013

FOC

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Object During the presurgical evaluation of patients with medically intractable focal epilepsy, a variety of noninvasive studies are performed to localize the hypothetical epileptogenic zone and guide the resection. Magnetoencephalography (MEG) is becoming increasingly used in the clinical realm for this purpose. No investigators have previously reported on coregisteration of MEG clusters with postoperative resection cavities to evaluate whether complete “clusterectomy” (resection of the area associated with MEG clusters) was performed or to compare these findings with postoperative seizure-free outcomes. Methods The authors retrospectively reviewed the charts and imaging studies of 65 patients undergoing MEG followed by resective epilepsy surgery from 2009 until 2012 at the Cleveland Clinic. Preoperative MEG studies were fused with postoperative MRI studies to evaluate whether clusters were within the resected area. These data were then correlated with postoperative seizure freedom. Results Sixty-five patients were included in this study. The average duration of follow-up was 13.9 months, the mean age at surgery was 23.1 years, and the mean duration of epilepsy was 13.7 years. In 30 patients, the main cluster was located completely within the resection cavity, in 28 it was completely outside the resection cavity, and in 7 it was partially within the resection cavity. Seventy-four percent of patients were seizure free at 12 months after surgery, and this rate decreased to 60% at 24 months. Improved likelihood of seizure freedom was seen with complete clusterectomy in patients with localization outside the temporal lobe (extra–temporal lobe epilepsy) (p = 0.04). Conclusions In patients with preoperative MEG studies that show clusters in surgically accessible areas outside the temporal lobe, we suggest aggressive resection to improve the chances for seizure freedom. When the cluster is found within the temporal lobe, further diagnostic testing may be required to better localize the epileptogenic zone.

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“…The relatively large inaccuracy of the signals in MEG and fNIRS for depths beyond 30 mm suggests that it is prohibitively difficult to image deep brain sources, such as subcortical regions, with these methods. Previously, this falloff of signal with depth had been modeled using simulated data, [46][47][48] but the current work provides an empirical examination of this issue. One caveat of the current study is that it is done in the context of median nerve stimulation, which provides a relative context for comparing localization.…”

Section: Comparision Of Fnirs Fmri and Meg Signalsmentioning

confidence: 97%

Comparison of group-level, source localized activity for simultaneous functional near-infrared spectroscopy-magnetoencephalography and simultaneous fNIRS-fMRI during parametric median nerve stimulation

et al. 2017

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Abstract. Functional near-infrared spectroscopy (fNIRS) is a noninvasive neuroimaging technique, which uses light to measure changes in cerebral blood oxygenation through sensors placed on the surface of the scalp. We recorded concurrent fNIRS with magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) in order to investigate the group-level correspondence of these measures with source-localized fNIRS estimates. Healthy participants took part in both a concurrent fNIRS-MEG and fNIRS-fMRI neuroimaging session during two somatosensory stimulation tasks, a blocked design median nerve localizer and parametric pulsed-pair median nerve stimulation using interpulse intervals from 100 to 500 ms. We found the spatial correlation for estimated activation patterns from the somatosensory task was R ¼ 0.54, 0.57, and −0.48 and the amplitude correlation was R ¼ 0.80, 0.52, and −0.70 for fMRI-MEG, fMRI-fNIRS oxy-hemoglobin, and fMRI-fNIRS deoxy-hemoglobin signals, respectively. Taken together, these results show good correspondence among the fMRI, fNIRS, and MEG with the great majority of the difference across modalities being driven by lower sensitivity for deeper brain sources in MEG and fNIRS. These results provide an important validation of source-localized fNIRS in the context of concurrent multimodal imaging for future studies of the relationship between physiological effects in the human brain.

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Mapping the signal‐to‐noise‐ratios of cortical sources in magnetoencephalography and electroencephalography

Cited by 234 publications

References 51 publications

Voices behind the left shoulder: Two patients with right-sided temporal lobe epilepsy

Voices behind the left shoulder: Two patients with right-sided temporal lobe epilepsy

Correlation between magnetoencephalography-based “clusterectomy” and postoperative seizure freedom

Comparison of group-level, source localized activity for simultaneous functional near-infrared spectroscopy-magnetoencephalography and simultaneous fNIRS-fMRI during parametric median nerve stimulation

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