Biology subjects

Feys, O.

Publications and source records attributed to Feys, O..

3 recordsLinked to original sources

bioRxiv2025

Fetal magnetoencephalography based on optically pumped magnetometers

The fetus in the third trimester of gestation has already the remarkable capacity to process external sensory information in utero. So far, investigations of fetal brain responses to sensory information have mostly relied on cryogenic magnetoencephalography (MEG), which is suitable to record fetal brain activity and is not much affected by layers of maternal tissues. Nevertheless, this solution is extremely expensive and limited to a couple of laboratories worldwide. In this work, we took advantage of the next generation cryogenic-free MEG, that is MEG based on optically pumped magnetometers (OPM), to develop a system that could record both fetal and newborn brain responses to auditory stimulation in a longitudinal design. Twenty-one pregnant women in their late third trimester of gestation (35-40 weeks of gestational age) were exposed to sequences of 500 Hz tones. Fetal brain activity was recorded using a wearable belt equipped with OPM sensors arranged on the womens abdomen based on fetal head position. Results revealed that fetal OPM-MEG successfully recorded significant evoked brain responses to auditory stimuli that peaked ~300 ms post-stimulus at the group level. A similar auditory paradigm was performed with on-scalp OPM-MEG in 14 one-month-old infants, with 9 participants common to both timepoints. Infant responses showed a significant latency decrease compared to the fetal ones in terms of magnetometers; a decrease that did not reach significance level for virtual gradiometers. This work demonstrates the ability of OPM-MEG to non-invasively record fetal brain responses to external sensory stimuli. It paves the way for a wider use of fetal MEG to investigate fetal cognition and positions OPM-MEG as the most promising lifespan-compliant solution for monitoring early brain development.

neuroscience↗

bioRxiv2023

Extending the applicability of optically pumped magnetoencephalography toward early human life

Characterizing the early development of the human brain is critical from both fundamental and clinical perspectives. However, existing neuroimaging techniques are either not well suited to infants or have limited spatial or temporal resolution. The advent of optically pumped magnetometers (OPMs) has revolutionized magnetoencephalography (MEG) by enabling wearable and thus more naturalistic recordings while maintaining excellent sensitivity and spatiotemporal resolution. Nevertheless, its adaptation to studying neural activity in infancy poses several challenges. In this work, we present an original close-to-scalp OPM-MEG setup that successfully recorded brain responses to sounds in newborns. We exposed one-month-old infants to continuous streams of tones and observed significant evoked responses, which peaked [~]250 ms poststimulus at bilateral auditory cortices. When tones were presented at a steady fixed pace with an oddball tone every fourth tone, significant neural responses were found both at the frequency of the standard tones (3 Hz) and of the oddball tones (0.75 Hz). The latter reflects the ability of the newborn brain to detect auditory change and synchronize to regular auditory patterns. Additional analyses support the added value of triaxial OPMs to increase the number of channels on small heads. Finally, OPM-MEG responses were validated with those obtained from the same participants using an adult-sized cryogenic MEG. This study demonstrates the applicability of OPM-MEG to study early postnatal periods; a crucial step towards future OPM investigations of typical and pathological early brain development.

neuroscience↗

bioRxiv2023

Towards the automated detection of interictal epileptiform discharges with magnetoencephalography

The analysis of clinical magnetoencephalography (MEG) in patients with epilepsy traditionally relies on the visual identification of interictal epileptiform discharges (IEDs), which is time consuming and dependent on (subjective) human criteria. Data-driven approaches enabling both spatial and temporal localization of epileptic spikes would represent a major leap forward in clinical MEG practice. Here, we explore the ability of Independent Components Analysis (ICA) and Hidden Markov Modeling (HMM) to automatically detect and localize IEDs. Combined with kurtosis mapping, we developed a fully automated identification of epileptiform independent components (ICs) or HMM states. We tested our pipeline on MEG recordings at rest from 10 school-age children with either focal or multifocal epilepsy and compared results with the traditional MEG analysis performed by an experienced clinical magnetoencephalographer. In patients with focal epilepsy, both ICA- and HMM-based pipelines successfully detected visually identified IEDs with high sensitivity, but also revealed low-amplitude IEDs unidentified by the visual detection. Success was more mitigated in patients with multifocal epilepsy, as our automated pipeline missed IED activity associated with some foci--an issue that could be alleviated by post-hoc manual selection of epileptiform ICs or HMM states. Therefore, IED detection based on ICA or HMM represents an efficient way to identify spike localization and timing, with heightened sensitivity to IEDs compared to visual MEG signal inspection and requiring minimal input from clinical practitioners.

neuroscience↗