Elena Boto

Tourette Syndrome (TS) is a neurodevelopmental hyperkinetic disorder characterised by involuntary tics. These tics are thought to arise due to hyperexcitability of the motor cortex due to disinhibition within the cortico-striato-thalamo-cortical pathway. Given the involvement of motor circuits in this disorder, we explored whether there is a difference in the oscillatory dynamics of voluntary movements in people with tic disorders. We recorded optically pumped magnetometer magnetoencephalography during cued voluntary finger abductions in individuals with tic disorders and age- and sex-matched neurotypical controls. We analysed the data both using conventional time frequency analysis and using hidden Markov modelling to explore the difference in beta burst characteristics and dynamics. Whilst no differences were seen between groups during conventional analysis, we demonstrated an increase in beta burst duration during the post-movement beta rebound within the contralateral motor cortex in individuals with TS suggestive of increased inhibition following movement. We also show evidence of increased contralateral sensorimotor functional connectivity and reduced connectivity from and between frontal regions, as measured using coincident beta bursts. This is suggestive of disrupted functional connectivity within frontal control networks in individuals with TS.

Beta oscillations are a fundamental feature of brain activity, linked to long-range connectivity within canonical networks, inhibition of sensorimotor cortices and the maintenance of a stable sensorimotor state in situations where the external world is predictable. The importance of beta oscillations in brain function is underscored by observations of their perturbation in neurological and psychiatric disorders. However, the precise role played by beta activity, particularly in mediating complex or skilful movements, remains incompletely understood. Here, we used a newly developed wearable optically pumped magnetometer-based magnetoencephalography (OPM-MEG) system to measure beta dynamics as participants learned to play a musical instrument. Twenty-two novice players took part in a study in which OPM-MEG data were recorded during two scanning sessions, while participants attempted to play a tune on a violin. Between the two sessions, participants received a violin lesson from an expert teacher. Results showed that robust data could be acquired during this naturalistic task, with beta oscillations decreasing in amplitude during movement and increasing upon movement cessation, as expected. Moreover, beta power whilst playing, in the motor and pre-motor areas, was significantly elevated after the lesson compared to before, and the movement-related modulation of beta amplitude was more pronounced after the lesson. These findings align with predictive coding models which suggest that beta amplitude should increase when individuals have greater certainty over the movements they carry out. Our study adds to an expanding literature on the role of beta oscillations and provides further evidence for the utility of OPM-MEG in naturalistic neuroscience.

Optically pumped magnetometers (OPMs) have emerged as a viable alternative to superconducting quantum interference devices (SQUIDs) to measure the magnetic fields generated by brain activity. Magnetoencephalography (MEG) systems based on OPMs offer potential advantages over conventional systems. However, there remains a pressing need for techniques and studies that demonstrate equivalence between emergent OPM-based instruments and the established conventional MEG standard. Here, we seek to demonstrate similarities between a 192-channel (64-triaxial sensor) OPM-based system and a 275-channel SQUID-based system, when measuring data during a sensory task designed elicit induced oscillatory (beta-band) and evoked responses as well as subtle attentional effects. We reasoned that in addition to measuring these primary responses (which are stable across individuals), neural fingerprinting (i.e., demonstrating that an individual’s OPM-MEG data can be identified from a group, by matching to their SQUID data) would determine whether subtle but repeatable differences between individuals are also measurable across OPM and SQUID-based platforms. Our results showed (1) that primary responses are measurable using both systems with correlations of 0.96 (beta responses) and 0.97 (evoked responses) at the group level; (2) both systems captured significant attentional modulation of the beta rhythm; and (3) fingerprinting was successful in 15 of 15 people using OPM-MEG, 14 of 15 people using SQUID-MEG, and 15 of 15 people when examining cross-platform data. Overall, our results confirm that the two MEG platforms capture similar information on brain function. This is an important step towards proving equivalence between OPMs and SQUIDs, which in turn is required if OPMs are to replace SQUIDs for clinical evaluations.

Electroencephalography (EEG) and magnetoencephalography (MEG) non-invasively measure human brain electrophysiology. They differ in nature; MEG offers better performance (higher spatial precision) whilst EEG (a wearable platform) is more practical. They are also complementary, with studies showing that concurrent MEG/EEG provides advantages over either modality alone, and consequently clinical guidelines for MEG in epilepsy recommend simultaneous acquisition of EEG. In recent years, new instrumentation – optically pumped magnetometers (OPMs) – has had a significant impact on MEG, offering improved performance, lifespan compliance, and wearable sensors. Nevertheless, the ability to carry out simultaneous EEG/OPM-MEG remains critical. Here, we investigated whether simultaneous, wearable, whole-head EEG and OPM-MEG measurably degrades signal quality in either modality. We employed two tasks: a motor task known to modulate beta oscillations, and an eyes-open/eyes-closed task known to modulate alpha oscillations. In both, we characterised the performance of EEG alone, MEG alone, and concurrent EEG/OPM-MEG. Our results show that the SNR of the beta response was very similar, regardless of whether modalities were used individually or concurrently. Likewise, our alpha band recordings demonstrated that signal contrast was stable, regardless of the concurrent recording. These results combined suggest that there are no fundamental barriers to simultaneous wearable EEG/OPM-MEG, and consequently this technique is ripe for neuroscientific and clinical adoption. This will be particularly important in the clinical sphere where a direct comparison between simultaneous EEG and OPM-MEG recordings will facilitate interpretation of OPM-MEG data in patients.

Background: Brain-computer interfaces decode intentions directly from the human brain with the aim to restore lost functionality, control external devices or augment daily experiences. To combine optimal performance with wide applicability, high-quality brain signals should be captured non-invasively. Magnetoencephalography (MEG) is a potent candidate but currently requires costly and confining recording hardware. The recently developed optically pumped magnetometers (OPMs) promise to overcome this limitation, but are currently untested in the context of neural interfacing. Results: In this work, we show that OPM-MEG allows robust single-trial analysis which we exploited in a real-time ‘mind-spelling’ application yielding an average accuracy of 97.7%. Conclusions: This shows that OPM-MEG can be used to exploit neuro-magnetic brain responses in a practical and flexible manner, and opens up new avenues for a wide range of new neural interface applications in the future.