Author name cluster

Lukas Rier

Possible papers associated with this exact author name in Arrow. This page groups case-insensitive exact name matches and is not a full identity disambiguation profile.

5 papers

1 author row

YNICL Journal 2025 Journal Article

OPM-MEG in multiple sclerosis: Proof of principle, and the effect of naturalistic posture

Benjamin J. Sanders
Christopher G.S. Gilmartin
Lukas Rier
Lauren Gascoyne
Emily McCann
Jorge Cabrera
James Leggett
Niall Holmes

Multiple Sclerosis (MS) is a common neurological disorder in which myelin damage affects neuronal signalling. Magnetoencephalography (MEG - the measurement of magnetic fields generated by neuronal currents) offers metrics of brain function that relate directly to electrophysiological signalling, making it a valuable tool for exploring how abnormal function relates to MS symptoms. However, conventional MEG requires participants to be seated or supine with limited head and body motion. This makes it hard to measure brain function whilst simultaneously asking patients to carry out tasks they find challenging - many of which relate to movement. Here, we used a newly developed OPM-MEG system, with a wearable helmet and a lightweight backpack-mounted control unit, to measure MEG signals in people with MS (pwMS), both at rest and during a visuo-motor task. Uniquely, our system enabled data collection in participants who were seated and standing. We found that established markers of MS - including delayed beta-band responses to finger movement and diminished gamma-band responses to visual stimulation - were measurable using OPM-MEG. Further, we showed that standing (compared to sitting) decreased beta-band connectivity (in patients and controls, but the effect was only significant in controls) and decreased oscillatory power (in patients but not controls). In summary, our paper confirms that OPM-MEG is a useful means to investigate MS; it also demonstrates the importance of investigating how changes in posture relate to oscillations and connectivity, and lays the groundwork for broader studies of movement.

Details DOI

YNIMG Journal 2023 Journal Article

Enabling ambulatory movement in wearable magnetoencephalography with matrix coil active magnetic shielding

Niall Holmes
Molly Rea
Ryan M. Hill
James Leggett
Lucy J. Edwards
Peter J. Hobson
Elena Boto
Tim M. Tierney

The ability to collect high-quality neuroimaging data during ambulatory participant movement would enable a wealth of neuroscientific paradigms. Wearable magnetoencephalography (MEG) based on optically pumped magnetometers (OPMs) has the potential to allow participant movement during a scan. However, the strict zero magnetic field requirement of OPMs means that systems must be operated inside a magnetically shielded room (MSR) and also require active shielding using electromagnetic coils to cancel residual fields and field changes (due to external sources and sensor movements) that would otherwise prevent accurate neuronal source reconstructions. Existing active shielding systems only compensate fields over small, fixed regions and do not allow ambulatory movement. Here we describe the matrix coil, a new type of active shielding system for OPM-MEG which is formed from 48 square unit coils arranged on two planes which can compensate magnetic fields in regions that can be flexibly placed between the planes. Through the integration of optical tracking with OPM data acquisition, field changes induced by participant movement are cancelled with low latency (25 ms). High-quality MEG source data were collected despite the presence of large (65 cm translations and 270° rotations) ambulatory participant movements.

Details DOI

YNIMG Journal 2023 Journal Article

Measurement of Frontal Midline Theta Oscillations using OPM-MEG

Natalie Rhodes
Molly Rea
Elena Boto
Lukas Rier
Vishal Shah
Ryan M. Hill
James Osborne
Cody Doyle

Optically pumped magnetometers (OPMs) are an emerging lightweight and compact sensor that can measure magnetic fields generated by the human brain. OPMs enable construction of wearable magnetoencephalography (MEG) systems, which offer advantages over conventional instrumentation. However, when trying to measure signals at low frequency, higher levels of inherent sensor noise, magnetic interference and movement artefact introduce a significant challenge. Accurate characterisation of low frequency brain signals is important for neuroscientific, clinical, and paediatric MEG applications and consequently, demonstrating the viability of OPMs in this area is critical. Here, we undertake measurement of theta band (4-8 Hz) neural oscillations and contrast a newly developed 174 channel triaxial wearable OPM-MEG system with conventional (cryogenic-MEG) instrumentation. Our results show that visual steady state responses at 4 Hz, 6 Hz and 8 Hz can be recorded using OPM-MEG with a signal-to-noise ratio (SNR) that is not significantly different to conventional MEG. Moreover, we measure frontal midline theta oscillations during a 2-back working memory task, again demonstrating comparable SNR for both systems. We show that individual differences in both the amplitude and spatial signature of induced frontal-midline theta responses are maintained across systems. Finally, we show that our OPM-MEG results could not have been achieved without a triaxial sensor array, or the use of postprocessing techniques. Our results demonstrate the viability of OPMs for characterising theta oscillations and add weight to the argument that OPMs can replace cryogenic sensors as the fundamental building block of MEG systems.

Details DOI

YNICL Journal 2021 Journal Article

Magnetoencephalography abnormalities in adult mild traumatic brain injury: A systematic review

Christopher M. Allen
Lloyd Halsey
Gogem Topcu
Lukas Rier
Lauren E. Gascoyne
John W Scadding
Paul L. Furlong
Benjamin T. Dunkley

BACKGROUND: The global incidence of traumatic brain injuries is rising, with at least 80% being classified as mild. These mild injuries are not visible on routine clinical imaging. The potential clinical role of a specific imaging biomarker be it diagnostic, prognostic or directing and monitoring progress of personalised treatment and rehabilitation has driven the exploration of several new neuroimaging modalities. This systematic review examined the evidence for magnetoencephalography (MEG) to provide an imaging biomarker in mild traumatic brain injury (mTBI). METHODS: Our review was prospectively registered on PROSPERO: CRD42019151387. We searched EMBASE, MEDLINE, trial registers, PsycINFO, Cochrane Library and conference abstracts and identified 37 papers describing MEG changes in mTBI eligible for inclusion. Since meta-analysis was not possible, based on the heterogeneity of reported outcomes, we provide a narrative synthesis of results. RESULTS: The two most promising MEG biomarkers are excess resting state low frequency power, and widespread connectivity changes in all frequency bands. These may represent biomarkers with potential for diagnostic application, which reflect time sensitive changes, or may be capable of offering clinically relevant prognostic information. In addition, the rich data that MEG produces are well-suited to new methods of machine learning analysis, which is now being actively explored. INTERPRETATION: MEG reveals several promising biomarkers, in the absence of structural abnormalities demonstrable with either computerised tomography or magnetic resonance imaging. This review has not identified sufficient evidence to support routine clinical use of MEG in mTBI currently. However, verifying MEG's potential would help meet an urgent clinical need within civilian, sports and military medicine.

Details DOI

YNICL Journal 2021 Journal Article

Mild traumatic brain injury impairs the coordination of intrinsic and motor-related neural dynamics

Lukas Rier
Rouzbeh Zamyadi
Jing Zhang
Zahra Emami
Zelekha A. Seedat
Sergiu Mocanu
Lauren E. Gascoyne
Christopher M. Allen

Mild traumatic brain injury (mTBI) poses a considerable burden on healthcare systems. Whilst most patients recover quickly, a significant number suffer from sequelae that are not accompanied by measurable structural damage. Understanding the neural underpinnings of these debilitating effects and developing a means to detect injury, would address an important unmet clinical need. It could inform interventions and help predict prognosis. Magnetoencephalography (MEG) affords excellent sensitivity in probing neural function and presents significant promise for assessing mTBI, with abnormal neural oscillations being a potential specific biomarker. However, growing evidence suggests that neural dynamics are (at least in part) driven by transient, pan-spectral bursting and in this paper, we employ this model to investigate mTBI. We applied a Hidden Markov Model to MEG data recorded during resting state and a motor task and show that previous findings of diminished intrinsic beta amplitude in individuals with mTBI are largely due to the reduced beta band spectral content of bursts, and that diminished beta connectivity results from a loss in the temporal coincidence of burst states. In a motor task, mTBI results in diminished burst amplitude, altered modulation of burst probability during movement, and a loss in connectivity in motor networks. These results suggest that, mechanistically, mTBI disrupts the structural framework underlying neural synchrony, which impairs network function. Whilst the damage may be too subtle for structural imaging to see, the functional consequences are detectable and persist after injury. Our work shows that mTBI impairs the dynamic coordination of neural network activity and proposes a potent new method for understanding mTBI.

Details DOI