Testing covariance models for MEG source reconstruction of hippocampal activity

O'Neill, George; Barry, Daniel N.; Tierney, Tim M.; Mellor, Stephanie; Maguire, Eleanor A.; Barnes, Gareth R.

doi:10.1038/s41598-021-96933-0

Cited by 9 publications

(9 citation statements)

References 76 publications

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“…We have shown that conventional MEG analysis of eyes-open resting state data gives rise to an apparent high-frequency anterior temporal network which is reproducible across 100 Hz bands up until 400 Hz. These networks appear to be reproduciblenot only did we observe this in the Human Connectome Project resting state data, but similar topographies were also found in a 22-subject, task-based dataset collected in a previous study (Barry et al, 2019;O'Neill et al, 2021) that employed a different MEG system in a different country. Using the complimentary empty-room recordings of the HCP dataset we cannot simply replicate the network topographies without recording from the brain of a person within the MEG scanner (supplementary material).…”

Section: Discussionsupporting

confidence: 85%

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Is high-frequency activity evidence of an anterior temporal lobe network or micro-saccades?

O'Neill

Mellor

Seymour

et al. 2023

Preprint

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There is renewed interest in electrical activity that extends beyond the typical electrophysiological 100 Hz bandwidth. This activity, often in the anterior temporal lobe, has been attributed to processes ranging from memory consolidation to epileptiform activity. Here, using an open-access resting state magnetoencephalography (MEG) dataset (n = 89), and a second task-based MEG dataset, we could reliably localise high-frequency power to the temporal lobes across multiple bands up to 300-400 Hz. A functional connectivity analysis of this activity revealed a robust resting state bilateral network between the temporal lobes. However, we also found robust coherence in the 100-200 and 200-300 Hz bands between source reconstructed MEG data and the electrooculography (EOG) localised to within the temporal poles. Additional denoising schemes applied to the data could reduce power localisation to the temporal poles but the topography of the functional network did not drastically alter. Whilst it is clear that this network is biological and robust to established denoising methods, we cannot definitively rule yet on whether this is of neural or myogenic origin.

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Section: Discussionsupporting

confidence: 85%

“…We also analysed a second task-based dataset, which has been explored in previous studies (Barry et al, 2019; O’Neill et al, 2021). 22 native English speakers (14 female, aged 27±7 [mean±SD] years) participated in study that involved generating novel scene imagery.…”

Section: Methodsmentioning

confidence: 99%

Is high-frequency activity evidence of an anterior temporal lobe network or micro-saccades?

O'Neill

Mellor

Seymour

et al. 2023

Preprint

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“…There are several considerations when using beamformers with OPM data. First, traditional beamformers tend to fail in situations of highly correlated neuronal sources ( Van Veen et al., 1997 ), for example during binaural auditory stimulation ( Popov et al., 2018 ), or cognitive tasks involving bilateral hippocampi ( O'Neill et al., 2021 ). However, there are sparse source reconstruction techniques that are more robust to correlated sources such as “champagne” ( Cai et al., 2021 ; Owen et al., 2012 ), or “Multiple Sparse Priors” for correlated priors ( Friston et al., 2008 ; López et al., 2014).…”

Section: Signal Processing Strategies For Opmsmentioning

confidence: 99%

Interference suppression techniques for OPM-based MEG: Opportunities and challenges

et al. 2022

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One of the primary technical challenges facing magnetoencephalography (MEG) is that the magnitude of neuromagnetic fields is several orders of magnitude lower than interfering signals. Recently, a new type of sensor has been developed – the optically pumped magnetometer (OPM). These sensors can be placed directly on the scalp and move with the head during participant movement, making them wearable. This opens up a range of exciting experimental and clinical opportunities for OPM-based MEG experiments, including paediatric studies, and the incorporation of naturalistic movements into neuroimaging paradigms. However, OPMs face some unique challenges in terms of interference suppression, especially in situations involving mobile participants, and when OPMs are integrated with electrical equipment required for naturalistic paradigms, such as motion capture systems. Here we briefly review various hardware solutions for OPM interference suppression. We then outline several signal processing strategies aimed at increasing the signal from neuromagnetic sources. These include regression-based strategies, temporal filtering and spatial filtering approaches. The focus is on the practical application of these signal processing algorithms to OPM data. In a similar vein, we include two worked-through experiments using OPM data collected from a whole-head sensor array. These tutorial-style examples illustrate how the steps for suppressing external interference can be implemented, including the associated data and code so that researchers can try the pipelines for themselves. With the popularity of OPM-based MEG rising, there will be an increasing need to deal with interference suppression. We hope this practical paper provides a resource for OPM-based MEG researchers to build upon.

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“…A subset of these same regions were involved in the theta/alpha changes found during 18 to 19s of overlap compared to non-overlap video-watching (Fig 2.B), including the Inferior parietal lobe, hippocampus, retrosplenial cortex, and precuneus. Although the effect appears to be isolated to the right hemisphere, we do not make inferences about the lateralisation because the beamformer algorithm can output illusory lateralised effects (O’Neill et al, 2021).…”

Section: Resultsmentioning

confidence: 99%

Theta and alpha oscillations in human hippocampus and medial parietal cortex support the formation of location-based representations

Satish,

Keller,

Raza

et al. 2023

Preprint

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Our ability to navigate in a new environment depends on learning new locations. Mental representations of locations are quickly accessible during navigation and allow us to know where we are regardless of our current viewpoint. Recent fMRI research has shown that these location-based representations emerge in the retrosplenial cortex and parahippocampal gyrus, regions theorised to be critically involved in spatial navigation. However, little is currently known about the oscillatory dynamics that support the formation of location-based representations. We used MEG to investigate region-specific oscillatory activity related to forming location-based representations. Participants viewed videos showing that two perceptually distinct scenes (180 degrees apart) belonged to the same location. This 'overlap' video allowed participants to bind the two distinct scenes together into a more coherent location-based representation. Participants also viewed control 'non-overlap' videos where two distinct scenes from two different locations were shown, where no location-based representation could be formed. In a post-video behavioural task, participants successfully matched the two viewpoints shown in the overlap videos, but not the non-overlap videos, indicating they successfully learned the locations in the overlap condition. Comparing oscillatory activity between the overlap and non-overlap videos, we found greater theta and alpha/beta power during the overlap relative to non-overlap videos, specifically at time-points when we expected scene integration to occur. These oscillations localised to regions in the medial parietal cortex (precuneus and retrosplenial cortex) and the medial temporal lobe, including the hippocampus. Therefore, we find that theta and alpha/beta oscillations in the hippocampus and medial parietal cortex are involved in the formation of location-based representations.

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Testing covariance models for MEG source reconstruction of hippocampal activity

Cited by 9 publications

References 76 publications

Is high-frequency activity evidence of an anterior temporal lobe network or micro-saccades?

Is high-frequency activity evidence of an anterior temporal lobe network or micro-saccades?

Interference suppression techniques for OPM-based MEG: Opportunities and challenges

Theta and alpha oscillations in human hippocampus and medial parietal cortex support the formation of location-based representations

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