New brain scan tool reveals key insights into childhood brain development

In a recent study published in the journal eLife, researchers evaluate the feasibility of optically pumped magnetometer-based magnetoencephalography (OPM-MEG) for monitoring neural oscillations during brain development.

Study: Tracking the neurodevelopmental trajectory of beta band oscillations with optically pumped magnetometer-based magnetoencephalography. Image Credit: peterschreiber.media / Shutterstock.com

What are neural oscillations?

Neural oscillations, particularly beta oscillations, are essential for brain function and play an important role in long-distance connections, especially attentional networks. Recognizing these processes is critical to understanding the causes of neurological diseases and mental illnesses.

Beta oscillations and their modulation can identify abnormalities in conditions such as autism, multiple sclerosis, Parkinson’s disease, and schizophrenia. Studying the neurodevelopmental course of beta oscillations might provide novel insights into normal and aberrant function; however, technological constraints limit these investigations.

About the study

In the present study, researchers used the 192-channel OPM-MEG platform to explore the developmental trajectory of beta oscillations among individuals between two and 34 years of age and the accompanying developmental alterations.

Experimental setup and beta band modulation during sensory task. (A) 4-year-old child wearing an optically pumped magnetometer-based magnetoencephalography (OPM-MEG) helmet (consent and authorization for publication were obtained). (B) Schematic diagram of the whole system inside the shielded room. (C) Schematic illustration of stimulus timings and a photo of the somatosensory stimulators. ‘Braille’ stimulators each comprise eight pins, which can be controlled independently; all eight were used simultaneously to deliver the stimuli.

High-fidelity electrophysiological data were obtained during a passive somatosensory task that anybody, regardless of age, could accomplish to assess stimulus-induced modulation of beta oscillations in the sensory cortex and whole-brain connectivity. The current study included 27 children between two and 13 years of age, 17 of whom were female, as well as 26 adults between 21 and 34 years of age, 13 of whom were female.

OPM-MEG had over 64 OPMs that detected magnetic fields across three orthogonal planes. Sensors were attached to three-dimensionally designed helmets of various sizes, thereby enabling customization of the participant’s head. The helmet’s weight ranged between 856 and 906 grams.

The technology was incorporated into magnetically shielded rooms (MSR) with active field controls to enable background field reduction and participant movement during scanning while preserving sensor operation.

All study participants completed a task wherein two stimulators consecutively applied passive somatosensory stimulations to the right little or index finger.

Each stimulus was applied for 0.5 seconds, repeated in a 3.5-second interval, and included tapping thrice on the fingertips. This stimulation pattern was repeated 42 times in both fingers. For comparison, data were averaged within each group and among all 24 individuals.

The highest difference in beta band amplitude between the stimulation and after stimulation periods was determined and plotted it against age. The amplitude envelope correlation (AEC) between unaveraged beta band signals collected from 78 cortical areas was also measured to evaluate functional connectivity in the brain. A univariate, three-state hidden Markov model (HMM) on the broadband electrophysiological signal derived from the site of the highest beta modulation was used to examine pan-spectral bursts.

Data from a single participant (7 years of age). (A) Brain plots show slices through the left motor cortex, with a pseudo-T-statistical map of beta modulation. The blue/green peaks indicate locations of largest beta modulation during stimulation for index finger trials (digit 2/D2), while the red/yellow peaks show the little finger (digit 5/D5). (B) Time-frequency spectra showing neural oscillatory amplitude modulation (fractional change in spectral amplitude relative to baseline measured in the 2.5–3 s window) for both fingers, using data extracted from the location of peak beta modulation (left sensorimotor cortex). Vertical lines indicate the time of the first braille stimulus. Note the beta amplitude reduction during stimulation, as expected.

Study findings

Stimulus-induced modulation of beta oscillations in the sensory cortex and whole-brain connectivity varies significantly with age. Pan-spectral bursts of electrophysiological activity were associated with increased task-induced beta modulations with age.

A modulation peak was observed in the left sensorimotor cortical region, with non-significant differences in the site of peak beta modulation between the little and index finger stimulations. Time-frequency spectrograms (TFSs) showed reduced beta amplitudes during stimulation for all groups, with the most pronounced effects observed in adults.

The connection patterns in children varied in intensity and spatial signature, with the visual network exhibiting the highest connectedness. The frontal and parietal regions alter the most with age, while the visual cortex has the lowest influence.

Positive Pearson correlations were observed between burst probability modulations and age, thus indicating that the shift in task-related beta modulations was due to burst probability variations. Bursts were less likely during stimulation, with the least pronounced effects among younger individuals.

Among adults, spectral power diminished with increasing frequencies, showing additional alpha and beta band peaks. Diminished high frequencies and elevated low frequencies were observed in children compared to adults.

As age increased, decreased low-frequency spectra content and increased high-frequency spectra content were observed. However, spectra content within alpha bands remained stable with non-significant correlations with age. The non-burst states were associated with similar patterns for age-related frequency content changes.

OPM-MEG was optimal for lifelong compliance with multiple helmet sizes and non-significant differences in scalp-to-sensor distance with age. The customizable OPM-MEG arrays performed well, and the helmets were comfortable.

The heat from sensors dissipated through convection and insulating material coverings. Active field management minimized the field, while triaxial sensors eliminated spatial aliasing and increased noise rejection.

Conclusions

OPM-MEG is a novel platform for measuring brain electrophysiology across ages. This technology combines MEG performance with the convenience of functional near-infrared spectroscopy (fNIRS) or electroencephalography (EEG), thus making it suitable for pediatric applications.

OPM-MEG can improve task-induced beta modulation and whole-brain functional connectivity with age to identify illnesses like autism and epilepsy in children as early as two years old. The system also provides data on coordinated brain activity and age-related maturity, with older individuals less likely to experience somatosensory cortex bursts. Nevertheless, the method has some limitations, including restricted helmet range, weight optimization, and the requirement for coil technology.