Ultra-low-noise EEG/MEG systems enable bimodal non-invasive detection of spike-like human somatosensory evoked responses at 1 kHz

Fedele, Tommaso; Scheer, Hans-Jürgen; Burghoff, M.; Curio, Gabriel; Körber, Rainer

doi:10.1088/0967-3334/36/2/357

Cited by 40 publications

(25 citation statements)

References 30 publications

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“…Our single-channel system based on a 45 mm diameter firstorder axial gradiometer has a total measured noise of 0.50 fT Hz −1/2 when operated inside a low noise dewar. 6 It should be noted that atomic magnetometers have also been used for biomagnetic measurements albeit with a significant larger noise of about 10 fT Hz −1/2 and a bandwidth of about 100 Hz as demonstrated by Alem et al 7 For a narrow bandwidth of about 10 Hz and a gradiometric setup inside a ferrite shield, Dang et al 8 reached 160 aT Hz −1/2 at 40 Hz.…”

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confidence: 97%

“…For instance, in MEG high frequency components in evoked brain activity could be more easily resolved, paving the way for non-invasive studies of spiking activity. 6,10 As we show below, improved sensitivity can be achieved by utilizing an ultra-low noise dewar and an increased pick-up coil. When expanding the approach to a multichannel system, larger coils place constraints on the localization accuracy of an activity at a depth z.…”

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confidence: 99%

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An ultra-sensitive and wideband magnetometer based on a superconducting quantum interference device

Storm

Hömmen

Drung

2017

Applied Physics Letters

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The magnetic field noise in superconducting quantum interference devices (SQUIDs) used for biomagnetic research such as magnetoencephalography or ultra-low-field nuclear magnetic resonance is usually limited by instrumental dewar noise. We constructed a wideband, ultra-low noise system with a 45 mm diameter superconducting pick-up coil inductively coupled to a current sensor SQUID. Thermal noise in the liquid helium dewar is minimized by using aluminized polyester fabric as superinsulation and aluminum oxide strips as heat shields, respectively. With a magnetometer pick-up coil in the center of the Berlin magnetically shielded room 2 (BMSR2) a noise level of around 150 aT Hz −1/2 is achieved in the white noise regime between about 20 kHz and the system bandwidth of about 2.5 MHz. At lower frequencies, the resolution is limited by magnetic field noise arising from the walls of the shielded room. Modeling the BMSR2 as a closed cube with continuous µ-metal walls we can quantitatively reproduce its measured field noise.Biomagnetism aims at the detection of magnetic fields generated by the human body. As these fields are typically in the range of femtotesla to picotesla when detected outside the human body, high sensitivity magnetometry is required. Traditionally, the preferred detectors are low critical temperature (low-T c ) superconducting quantum interference devices (SQUIDs) operated at liquid helium (LHe) temperatures. Owing to their exquisite sensitivity SQUIDs facilitated the measurements of magnetic fields of the brain, and commercial multichannel systems for magnetoencephalography (MEG) are available with a field noise of about 2 fT Hz −1/2 . SQUID performance is usually limited by the LHe dewar due to Johnson noise in the superinsulation comprised of aluminized foils and the thermal radiation shields made from copper mesh.

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confidence: 97%

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confidence: 99%

An ultra-sensitive and wideband magnetometer based on a superconducting quantum interference device

Storm

Hömmen

Drung

2017

Applied Physics Letters

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“…The SNR of EEGs can vary widely with different conditions as it is very susceptible to muscle artifact notably as well as interferences with outside noise [Islam et al, 2016]. This latter challenge might be potentially overcome by the use of a low-noise amplifier [Fedele et al, 2015], which could make it possible to obtain low noise recordings in the future. Prolonged clean recordings can be extremely valuable for FO identification, as data have the least artifacts in the high-frequency domain during sleep [Zijlmans et al, 2017].…”

Section: Discussionmentioning

confidence: 99%

Fast oscillations >40Hz localize the epileptogenic zone: an electrical source imaging study using high-density electroencephalography

Avigdor

Abdallah

Ellenrieder

et al. 2020

Preprint

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CONFLICTS OF INTEREST:None of the authors has any conflict of interested related to the submitted work. P a g e | 3 Avigdor et al. | Fast oscillations localize the epileptogenic zone ABSTRACT (245/250) Fast Oscillations (FO) are a promising biomarker of the epileptogenic zone (EZ) in the intracranial electroencephalogram (EEG). Evidence using scalp EEG remains scarce. This is the first study that assesses if electrical source imaging of FO using 256-channel high-density EEG is feasible and useful for EZ identification. We analyzed high-density EEG recordings of 10 focal drug-resistant epilepsy patients with seizure-free postsurgical outcome (follow-up >2 years). We marked FO candidate events at the time of epileptic spikes and then verified them by screening for an isolated peak in the time-frequency plot. We performed electrical source imaging of FOs >40 Hz and spikes using the coherent Maximum Entropy of the Mean technique. Source localization maps were validated against the surgical cavity as approximation of the EZ. We identified FO events in 5 of the 10 patients. FOs were localizable in all 5 patients. The depth of the epileptic generator was either superficial or intermediate in all 5 patients with FO. The maximum of the FO maps was localized in the surgical cavity. We identified spikes in all 10 patients. Spikes were localized to the surgical cavity in 9 of 10 patients. In summary, FOs recorded with high-density EEG are able to localize the EZ. Our findings suggest that the presence of FOs co-localized with spikes points to a surface-close generator. These results can act as a proof of concept for future examination of FOs localization using scalp 256-channel high-density EEG as a viable marker of the EZ. Key words: high-density electroencephalography, epilepsy, maximum entropy of the mean, electrical source imaging, non-invasive localization P a g e | 4 Avigdor et al. | Fast oscillations localize the epileptogenic zone INTRODUCTION Epilepsy is a chronic condition characterized by recurrent seizures accompanied by negative impact on quality of life [Hinnell et al., 2010]. A significant number of 30% of patients with focal epilepsy are drug-resistant, and these numbers did not change over the past 30 years despite the development of multiple new antiepileptic drugs [Chen et al., 2018]. The therapy of choice for focal drug-resistant epilepsy is epilepsy surgery [Vakharia et al., 2018]. The aim of epilepsy surgery is to remove the epileptogenic zone (EZ) defined as the area of cortex that needs to be removed to achieve seizure freedom [Rosenow and Lüders, 2001]. In current praxis, the seizure-onset zone (SOZ) is used as the main proxy marker for the EZ. A sustained seizure-free condition is currently, however, obtained in only 50% of carefully selected patients [Krucoff et al., 2017; Mohan et al., 2018; West et al., 2019]. This is likely due to inaccurate localization of the EZ or a network involvement larger than initially expected [Englot, 2018]. This underlines the need to develop new markers and localiz...

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“…Events in the brain occur on a wide range of time scales, from those of molecular mechanisms to behavior, learning, and maturation. The events in the fast end of the spectrum are too brief to be measured with noninvasive electromagnetic recordings, such as electroencephalography or magnetoencephalography, which are limited to time scales of 1 ms at best (Fedele et al, ). Faster phenomena have been studied, for example, by invasive single‐cell recordings, such as the patch‐clamp method (Bean, ).…”

Section: Introductionmentioning

confidence: 99%

Noninvasive extraction of microsecond‐scale dynamics from human motor cortex

Koponen

Nieminen

Mutanen

et al. 2018

Human Brain Mapping

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State-of-the-art noninvasive electromagnetic recording techniques allow observing neuronal dynamics down to the millisecond scale. Direct measurement of faster events has been limited to in vitro or invasive recordings. To overcome this limitation, we introduce a new paradigm for transcranial magnetic stimulation. We adjusted the stimulation waveform on the microsecond scale, by varying the duration between the positive and negative phase of the induced electric field, and studied corresponding changes in the elicited motor responses. The magnitude of the electric field needed for given motor-evoked potential amplitude decreased exponentially as a function of this duration with a time constant of 17 µs. Our indirect noninvasive measurement paradigm allows studying neuronal kinetics on the microsecond scale in vivo.

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Ultra-low-noise EEG/MEG systems enable bimodal non-invasive detection of spike-like human somatosensory evoked responses at 1 kHz

Cited by 40 publications

References 30 publications

An ultra-sensitive and wideband magnetometer based on a superconducting quantum interference device

An ultra-sensitive and wideband magnetometer based on a superconducting quantum interference device

Fast oscillations >40Hz localize the epileptogenic zone: an electrical source imaging study using high-density electroencephalography

Noninvasive extraction of microsecond‐scale dynamics from human motor cortex

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