Natalie Rhodes

Tremendous maturation in brain structure and function, underlying very rapid cognitive development, occurs in the early years of life, yet it has been difficult to obtain reliable measures of brain function over this period. A major challenge has been the difficulty of acquiring reliable neuroimaging data from awake young children, who often struggle to tolerate conventional imaging environments or remain still during scanning. Existing approaches each involves important compromises between spatial and temporal resolution, movement tolerance and practicality for use in early childhood. Optically pumped magnetometers (OPMs), a recent advance in magnetoencephalography (MEG) technology, are expanding the developmental neuroimaging toolkit. By enabling adaptable, wearable, and movement-tolerant MEG systems, OPMs retain the excellent spatial and temporal resolution of conventional cryogenic MEG technology while improving suitability for infants, toddlers, and young children. In this commentary, we briefly review the current functional neuroimaging toolkit used across development and discuss how OPMs are transforming the study of the developing brain. We highlight recent applications of OPMs to study early life, their potential for investigating brain–behaviour relationships and social interaction, and their promise for improving inclusion of clinical populations traditionally underrepresented in neuroimaging research. We also outline remaining technical and methodological challenges that should be addressed as the field continues to grow.

Moment-to-moment fluctuations in sustained attention impair goal-directed behaviour. Although distributed cortical networks support attentional control, the contribution of subcortical electrophysiology remains poorly understood. As a key regulator of arousal and consciousness, the central thalamus is ideally positioned to support sustained attention, but direct evidence in humans remains scarce. Here we leveraged rare intracranial recordings from the centromedian (CM) nucleus of the thalamus in children with epilepsy, a population predisposed to attention deficits. During an attentional set-shifting task, we identified a robust CM event-related potential (ERP) following trial onset, arising temporally between two canonical scalp ERPs (N1 and P2) measured concurrently. Across all task conditions, larger thalamic ERP amplitudes predicted faster trial-by-trial reaction times, whereas ERP amplitudes progressively declined with time-on-task, paralleling behavioural slowing. Together, these findings demonstrate that central thalamic responses predict moment-to-moment behavioural performance, providing direct human evidence that the central thalamus contributes to the neural processes underlying fluctuations in sustained attention.

Passive and task-based MEG responses have been extensively studied in clinical populations to identify signatures that could serve as markers for clinical diagnosis or to monitor progression of treatment. Establishing the reliability of these responses across repeat testing as a benchmark is therefore essential. Emerging MEG technology using optically pumped magnetometers (OPMs) promises a new era for MEG, enhancing both research capabilities and clinical applications. However, the test-retest reliability of various MEG responses measured by these new systems has not yet been characterised. In this study, we measured a range of neural responses to task and rest using a whole-head OPM-MEG system. We assessed the stability of these responses over time in five adult participants, each tested across five different days. Our findings indicated that the well-established face-sensitive M170 response shows reliable group amplitude and latency over time, with a standard deviation of only 1 ms in latency. We showed that induced responses were more variable than evoked. Passive MEG power (via movie-watching as a pseudo-resting state metric) particularly in the alpha band, demonstrated high consistency across sessions, aligning with conventional MEG literature. Our results demonstrate reliability of a range of MEG metrics and provide a benchmark for evaluating changes over successive recordings.

Source modelling in magnetoencephalography (MEG) infers the spatial origins of electrophysiological signals in the brain. Typically, this requires an anatomical MRI scan of the subject’s head, from which models of the magnetic fields generated by the brain (the forward model) are derived. Wearable MEG—based on optically pumped magnetometers (OPMs)—enables MEG measurement from participants who struggle to cope with conventional scanning environments (e.g., children), enabling study of novel cohorts. However, its value is limited if an MRI scan is still required for source modelling. Here we describe a method of warping template MRIs to 3D structured-light scans of the head, to generate “pseudo-MRIs”. We apply our method to data from 20 participants during a sensory task, measuring induced (beta band) responses and whole-brain functional connectivity. Results show that the group average locations of peak task-induced beta modulation were separated by 2.75 mm, when comparing real- and pseudo-MRI approaches. Group averaged time–frequency spectra were also highly correlated (Pearson correlation 0.99) as were functional connectome matrices (0.87) and global connectivity (0.98). In sum, our results demonstrate that source-localised OPM-MEG data, modelled with and without an individual MRI scan, can be comparable. While individual MRI scans remain the “gold standard” for OPM-MEG modelling, our method will be useful for future studies where MRI data capture is challenging.

Disruption of the balance between excitatory and inhibitory neurotransmission (E-I balance) is thought to underlie many neurodevelopmental disorders; however, its study is typically restricted to adults, animal models, and the lab-bench. Neurophysiological oscillations in the gamma frequency band relate closely to E-I balance, and a new technology—OPM-MEG—offers the possibility to measure such signals across the lifespan. We used OPM-MEG to measure gamma oscillations induced by visual stimulation in 101 participants, aged 2–34 years. We demonstrate a significantly changing spectrum with age, with low-amplitude broadband gamma oscillations in children and high-amplitude band limited oscillations in adults. We used a canonical cortical microcircuit to model these signals, revealing a significant decrease in the ratio of excitatory to inhibitory signalling with age in the superficial pyramidal neurons of the visual cortex. Our findings detail the first MEG metrics of gamma oscillations and their underlying generators from toddlerhood, providing a benchmark against which future studies can contextualise.

Source modelling in magnetoencephalography (MEG) maps the spatial origins of electrophysiological signals in the brain. Typically, this requires an anatomical MRI scan of the subject’s head, from which a model of the neuromagnetic field (the forward model) is derived. Wearable MEG – based on optically pumped magnetometers (OPMs) – enables MEG measurement from participants who struggle to cope with conventional scanning environments (e.g. children), enabling study of novel cohorts. However, its value is limited if an MRI scan is still required for source modelling. Here we describe a method of warping template MRIs to 3D structured-light scans of the head, to generate “pseudo-MRIs”. We apply our method using data from 20 participants during a sensory task, measuring induced (beta band) responses and whole-brain functional connectivity. Results show that the group average locations of peak task-induced beta modulation were separated by 2.75 mm, when comparing real- and pseudo-MRI approaches. Group averaged time-frequency spectra were also highly correlated (Pearson correlation 0.99) as were functional connectome matrices (0.87), and global connectivity (0.98). In sum, our results demonstrate that source-localized OPM-MEG data, modelled with and without an individual MRI scan can be similar. This will be useful for future studies where MRI data capture is challenging.

Disruption of the balance between excitatory and inhibitory neurotransmission (E-I balance) underlies theories of many neurodevelopmental disorders, however, its study is typically restricted to adults, animal models and the lab-bench. Neurophysiological oscillations in the gamma frequency band relate closely to E-I balance, and a new technology – OPM-MEG – offers the possibility to measure such signals across the lifespan. We used OPM-MEG to measure gamma oscillations induced by visual stimulation in >100 participants, aged 2-34 years. We demonstrate a significantly changing spectrum with age, with low amplitude broadband gamma oscillations in children and high amplitude band limited oscillations dominating in adults. We used a canonical cortical microcircuit to model these gamma signals, revealing significant age-related shifts in E-I balance in superficial pyramidal neurons in visual cortex. Our findings detail the first MEG metrics of gamma oscillations and their underlying generators from toddlerhood, providing a benchmark against which future studies can contextualise.

The evolution of human cognitive function is reliant on complex social interactions which form the behavioural foundation of who we are. These social capacities are subject to dramatic change in disease and injury; yet their supporting neural substrates remain poorly understood. Hyperscanning employs functional neuroimaging to simultaneously assess brain activity in two individuals and offers the best means to understand the neural basis of social interaction. However, present technologies are limited, either by poor performance (low spatial/temporal precision) or an unnatural scanning environment (claustrophobic scanners, with interactions via video). Here, we describe hyperscanning using wearable magnetoencephalography (MEG) based on optically pumped magnetometers (OPMs). We demonstrate our approach by simultaneously measuring brain activity in two subjects undertaking two separate tasks—an interactive touching task and a ball game. Despite large and unpredictable subject motion, sensorimotor brain activity was delineated clearly, and the correlation of the envelope of neuronal oscillations between the two subjects was demonstrated. Our results show that unlike existing modalities, OPM-MEG combines high-fidelity data acquisition and a naturalistic setting and thus presents significant potential to investigate neural correlates of social interaction.