Tri-axial rubidium and helium optically pumped magnetometers for on-scalp magnetoencephalography recording of interictal epileptiform discharges: a case study.

Cryogenic magnetoencephalography (MEG) enhances the presurgical assessment of refractory focal epilepsy (RFE). Optically pumped magnetometers (OPMs) are cryogen-free sensors that enable on-scalp MEG recordings. Here, we investigate the application of tri-axial OPMs [Rb (Rb-OPM) and He gas (He-OPM)] for the detection of interictal epileptiform discharges (IEDs).

Helium Optically Pumped Magnetometers Can Detect Epileptic Abnormalities as Well as SQUIDs as Shown by Intracerebral Recordings.

Magnetoencephalography based on superconducting quantum interference devices (SQUIDs) has been shown to improve the diagnosis and surgical treatment decision for presurgical evaluation of drug-resistant epilepsy. Still, its use remains limited because of several constraints such as cost, fixed helmet size, and the obligation of immobility. A new generation of sensors, optically pumped magnetometers (OPMs), could overcome these limitations.

A New Generation of OPM for High Dynamic and Large Bandwidth MEG: The He OPMs-First Applications in Healthy Volunteers.

MagnetoEncephaloGraphy (MEG) provides a measure of electrical activity in the brain at a millisecond time scale. From these signals, one can non-invasively derive the dynamics of brain activity. Conventional MEG systems (SQUID-MEG) use very low temperatures to achieve the necessary sensitivity.

Performance Analysis of Optically Pumped He Magnetometers vs. Conventional SQUIDs: From Adult to Infant Head Models.

Optically pumped magnetometers (OPMs) are new, room-temperature alternatives to superconducting quantum interference devices (SQUIDs) for measuring the brain's magnetic fields. The most used OPM in MagnetoEncephaloGraphy (MEG) are based on alkali atoms operating in the spin-exchange relaxation-free (SERF) regime. These sensors do not require cooling but have to be heated.

Analysis of Graphomotor Tests with Machine Learning Algorithms for an Early and Universal Pre-Diagnosis of Dysgraphia.

Five to ten percent of school-aged children display dysgraphia, a neuro-motor disorder that causes difficulties in handwriting, which becomes a handicap in the daily life of these children. Yet, the diagnosis of dysgraphia remains tedious, subjective and dependent to the language besides stepping in late in the schooling. We propose a pre-diagnosis tool for dysgraphia using drawings called graphomotor tests.

Helium-4 magnetometers for room-temperature biomedical imaging: toward collective operation and photon-noise limited sensitivity.

Optically-pumped magnetometers constitute a valuable tool for imaging biological magnetic signals without cryogenic cooling. Nowadays, numerous developments are being pursued using alkali-based magnetometers, which have demonstrated excellent sensitivities in the spin-exchange relaxation free (SERF) regime that requires heating to >100 °C. In contrast, metastable helium-4 based magnetometers work at any temperature, which allows a direct contact with the scalp, yielding larger signals and a better patient comfort.

Space-Time-Frequency Multi-Sensor Analysis for Motor Cortex Localization Using Magnetoencephalography.

Brain source imaging and time frequency mapping (TFM) are commonly used in magneto/electro encephalography (M/EEG) imaging. However, these methods suffer from important limitations. Source imaging is based on an ill-posed inverse problem leading to instability of source localization solutions, has a limited capacity to localize high frequency oscillations and loses its robustness for induced responses (ill-defined trigger).

Magnetoencephalography With Optically Pumped He Magnetometers at Ambient Temperature.

In this paper, we present the first proof of concept confirming the possibility to record magnetoencephalographic (MEG) signals with optically pumped magnetometers (OPMs) based on the parametric resonance of He atoms. The main advantage of this kind of OPM is the possibility to provide a tri-axis vector measurement of the magnetic field at room-temperature (the He vapor is neither cooled nor heated). The sensor achieves a sensitivity of 210 fT/ √ Hz in the bandwidth [2-300 Hz].

Evidence for a hierarchy of predictions and prediction errors in human cortex.

According to hierarchical predictive coding models, the cortex constantly generates predictions of incoming stimuli at multiple levels of processing. Responses to auditory mismatches and omissions are interpreted as reflecting the prediction error when these predictions are violated. An alternative interpretation, however, is that neurons passively adapt to repeated stimuli.

Modeling of entorhinal cortex and simulation of epileptic activity: insights into the role of inhibition-related parameters.

This paper describes a macroscopic neurophysiologically relevant model of the entorhinal cortex (EC), a brain structure largely involved in human mesio-temporal lobe epilepsy. This model is intervalidated in the experimental framework of ictogenesis animal model (isolated guinea-pig brain perfused with bicuculline). Using sensitivity and stability analysis, an investigation of model parameters related to GABA neurotransmission (recognized to be involved in epileptic activity generation) was performed.

Relationship between intracerebral gamma oscillations and slow potentials in the human sensorimotor cortex.

Changes in sensorimotor rhythms (mu, beta and gamma) and movement-related cortical potentials (MRCPs) are both generated principally by the contralateral sensorimotor areas during the execution of self-paced movement. They appear to reflect movement control mechanisms, which remain partially unclear. With the aim of better understanding their sources and significance, we recorded MRCPs and sensorimotor rhythms during and after self-paced movement using intracerebral electrodes in eight epileptic subjects investigated by stereoelectroencephalography.

Effect of age on anticipatory postural adjustments in unilateral arm movement.

Aging is frequently accompanied by a deterioration in postural control. Accordingly, the elderly adopt postural strategies in order to maintain balance. The purpose of this study was to compare anticipatory postural adjustments in (healthy) 10 young and 10 elderly subjects using electromyography (EMG) and biomechanical parameters.

Role of hypokinesia and bradykinesia in gait disturbances in Huntington's disease: a biomechanical study.

Objective: To evaluate specific patterns of locomotion in Huntington's disease (HD) and notably the respective roles of hypokinesia (i. e. a decrease in the amplitude of movement) and bradykinesia (i.

Abnormal cortical mechanisms in voluntary muscle relaxation in de novo parkinsonian patients.

This study aimed at elucidating how the cortical mechanism underlying the preparation and the postmovement phase of voluntary hand muscle relaxation is affected in Parkinson's disease. Event-related mu and beta (de)synchronization (ERD/S) related to voluntary muscle contraction and relaxation were recorded in 16 untreated, akineto-rigid, predominantly hemiparkinsonian patients. The results were compared with data from 10 age-matched, healthy subjects.

Relationship between oscillations in the basal ganglia and synchronization of cortical activity.

The functions of oscillations within the basal ganglia are poorly understood. We discuss in the present paper, the possible physiological or pathological roles of oscillatory activities within the basal ganglia, and their relationship to cortical oscillations. Three aspects are presented: 1.

Basic mechanisms of central rhythms reactivity to preparation and execution of a voluntary movement: a stereoelectroencephalographic study.

Objective: To localize the sources of mu, beta and gamma rhythms and to explore the functional significance of their reactivity.

Methods: We used the method of quantification of event-related desynchronization (ERD) and synchronization (ERS) to analyze the reactivity of intracerebral rhythms recorded in stereoelectroencephalography within the sensorimotor areas during the preparation and the execution of a simple self-paced hand movement. We recorded 3 epileptic subjects who were explored before a surgical treatment.