Optimising the sensing volume of OPM sensors for MEG source reconstruction

Bezsudnova, Yulia; Koponen, Lari M.; Barontini, Giovanni; Jensen, Ole; Kowalczyk, Anna

doi:10.1016/j.neuroimage.2022.119747

Cited by 10 publications

(4 citation statements)

References 46 publications

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“…To track the changes of the measured magnetic field in real-time, we use a combination of lock-in detection and a phase-locked loop (PLL) that ensures that the resonance condition is always fulfilled. The two sensing cells (C1 and C2) are paraffin-coated and have cylindrical internal dimensions of 1.00 cm in length and 0.95 cm in diameter [45]. The centres of the two cells are separated by d = 4 cm.…”

Section: The Nmor Gradiometer Sensormentioning

confidence: 99%

An optically pumped magnetic gradiometer for the detection of human biomagnetism

Cook,

Bezsudnova,

Koponen

et al. 2024

Quantum Sci. Technol.

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We realise an intrinsic optically pumped magnetic gradiometer based on non-linear magneto-optical rotation. We show that our sensor can reach a gradiometric sensitivity of 18 fT/cm/√Hz and can reject common mode homogeneous magnetic field noise with up to 30 dB attenuation. We demonstrate that our magnetic field gradiometer is sufficiently sensitive and resilient to be employed in biomagnetic applications. In particular, we are able to record the auditory evoked response of the human brain, and to perform real-time magnetocardiography in the presence of external magnetic field disturbances. Our gradiometer provides complementary capabilities in human biomagnetic sensing to optically pumped magnetometers, and opens new avenues in the detection of human biomagnetism.

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Section: The Nmor Gradiometer Sensormentioning

confidence: 99%

An optically pumped magnetic gradiometer for the detection of human biomagnetism

Cook,

Bezsudnova,

Koponen

et al. 2024

Quantum Sci. Technol.

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“…It is difficult to envisage a noninvasive technique for primates with physiologically relevant sampling frequency. Perhaps, novel MEG-techniques with quantum field sensors and improved depth resolution may develop into tomographic MEG for primate brains (Bezsudnova et al, 2022 ).…”

Section: Technical Obstaclesmentioning

confidence: 99%

How far neuroscience is from understanding brains

Roland

2023

Front. Syst. Neurosci.

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The cellular biology of brains is relatively well-understood, but neuroscientists have not yet generated a theory explaining how brains work. Explanations of how neurons collectively operate to produce what brains can do are tentative and incomplete. Without prior assumptions about the brain mechanisms, I attempt here to identify major obstacles to progress in neuroscientific understanding of brains and central nervous systems. Most of the obstacles to our understanding are conceptual. Neuroscience lacks concepts and models rooted in experimental results explaining how neurons interact at all scales. The cerebral cortex is thought to control awake activities, which contrasts with recent experimental results. There is ambiguity distinguishing task-related brain activities from spontaneous activities and organized intrinsic activities. Brains are regarded as driven by external and internal stimuli in contrast to their considerable autonomy. Experimental results are explained by sensory inputs, behavior, and psychological concepts. Time and space are regarded as mutually independent variables for spiking, post-synaptic events, and other measured variables, in contrast to experimental results. Dynamical systems theory and models describing evolution of variables with time as the independent variable are insufficient to account for central nervous system activities. Spatial dynamics may be a practical solution. The general hypothesis that measurements of changes in fundamental brain variables, action potentials, transmitter releases, post-synaptic transmembrane currents, etc., propagating in central nervous systems reveal how they work, carries no additional assumptions. Combinations of current techniques could reveal many aspects of spatial dynamics of spiking, post-synaptic processing, and plasticity in insects and rodents to start with. But problems defining baseline and reference conditions hinder interpretations of the results. Furthermore, the facts that pooling and averaging of data destroy their underlying dynamics imply that single-trial designs and statistics are necessary.

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“…Despite the plethora of simulations (Boto et al 2016, Iivanainen et al 2017, Tierney et al 2020, Beltrachini et al 2021, Bezsudnova et al 2022, Marhl et al 2022, Nugent et al 2022, Zahran et al 2022 and experimental studies comparing OPM-and SQUIDbased MEG, it is still not fully and comprehensively understood how these measurement sensors compare. On the one hand, OPMs are closer to the brain, thus picking up higher signal amplitudes and potentially demonstrating higher spatial resolution than SQUIDs.…”

Section: Introductionmentioning

confidence: 99%

Single-trial classification of evoked responses to auditory tones using OPM- and SQUID-MEG

Iivanainen,

Carter,

Trumbo

et al. 2023

J. Neural Eng.

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Objective:Optically pumped magnetometers (OPMs) are emerging as a near-room-temperature alternative to superconducting quantum interference devices (SQUIDs) for magnetoencephalography (MEG). In contrast to SQUIDs, OPMs can be placed in a close proximity to subject’s scalp potentially increasing the signal-to-noise ratio and spatial resolution of MEG. However, experimental demonstrations of these suggested benefits are still scarce. Here, to compare a 24-channel OPM-MEG system to a commercial whole-head SQUID system in a data-driven way, we quantified their performance in classifying single-trial evoked responses.Approach:We measured evoked responses to three auditory tones in six participants using both OPM- and SQUID-MEG systems. We performed pairwise temporal classification of the single-trial responses with linear discriminant analysis as well as multiclass classification with both EEGNet convolutional neural network and xDAWN decoding. Main results:OPMs provided higher classification accuracies than SQUIDs having a similar coverage of the left hemisphere of the participant. However, the SQUID sensors covering the whole helmet had classification scores larger than those of OPMs for two of the tone pairs, demonstrating the benefits of a whole-head measurement.Significance:The results demonstrate that the current OPM-MEG system provides high-quality data about the brain with room for improvement for high bandwidth non-invasive brain-computer interfacing.

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Optimising the sensing volume of OPM sensors for MEG source reconstruction

Cited by 10 publications

References 46 publications

An optically pumped magnetic gradiometer for the detection of human biomagnetism

An optically pumped magnetic gradiometer for the detection of human biomagnetism

How far neuroscience is from understanding brains

Single-trial classification of evoked responses to auditory tones using OPM- and SQUID-MEG

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