concept

MEG

Also known as: magnetoencephalography, Magnetoencephalography

Facts (78)

Sources
Adversarial testing of global neuronal workspace and ... - Nature nature.com Nature Apr 30, 2025 57 facts
formulaThe Phase Locking Value (PPC) for a specific trial is calculated as the difference in phase angle between the MEG time series and iEEG electrode at each time t and frequency f, defined as: θj,k(f,t) = θ(f,t)e1 or GED filter - θ(f,t)e2 or GED filter.
claimValidation of Global Neuronal Workspace Theory (GNWT) predictions using iEEG and MEG data was inconclusive, as no prefrontal iEEG electrodes showed the GNWT-predicted combination of an onset and offset response (BF01 > 3 for all prefrontal electrodes).
claimThe MEG results regarding GNWT predictions were sensitive to parameter choices, and signal leakage from posterior sites could not be ruled out.
measurementThe study evaluated predictions of neurobiological theories of consciousness using 256 participants performing the same behavioral task across three neuroimaging modalities: functional magnetic resonance imaging (fMRI; n = 120), magnetoencephalography (MEG; n = 102), and intracranial electroencephalography (iEEG; n = 34).
procedureResearchers used linear mixed models to track gamma frequency band (60–90 Hz) power changes from the MEG source time series across 15 posterior parcels and 11 prefrontal cortex (PFC) parcels.
measurementThe adversarial study of integrated information theory (IIT) and global neuronal workspace theory (GNWT) involved 256 human participants who viewed suprathreshold stimuli for variable durations while researchers measured neural activity using functional magnetic resonance imaging, magnetoencephalography, and intracranial electroencephalography.
procedureMEG cortical time-series analysis (N=65) extracted signals from cortical parcels in V1/V2, Prefrontal Cortex (PFC), and fusiform regions of interest, with category-selective signals obtained via a category-selective Generalized Eigenvalue Decomposition (GED) filter on fusiform activity.
measurementThe MEG study consisted of 1,440 total trials, organized into 10 runs with 4 blocks each, containing 34–38 trials per block.
measurementIn the MEG and iEEG experimental versions, stimuli were presented for durations of 0.5 s, 1.0 s, or 1.5 s, followed by a blank period to achieve a fixed trial length of 2.0 s, with additional random jitter (mean inter-trial interval of 0.4 s, range 0.2–2.0 s) to prevent periodic stimulus presentation.
procedureMEG source modelling utilized the dynamic statistical parametric mapping method based on depth-weighted minimum-norm estimates on epoched and baseline-corrected data.
procedureWithin-task category and orientation decoding were performed using a leave-one-run-out cross-validation scheme for fMRI data and a k-fold cross-validation scheme for MEG and iEEG data.
referenceThe MNE software package is designed for processing MEG and EEG data, as described in Gramfort et al., NeuroImage 86, 446–460 (2014).
measurementThe study's testing framework involved an initial optimization phase on one-third of the MEG (n = 32) and fMRI (n = 35) datasets to evaluate data quality and optimize analysis pipelines, followed by a preregistered replication phase on novel datasets (MEG n = 65 and fMRI n = 73).
procedureFor the MEG and fMRI datasets, one-third of the data that passed quality tests (the optimization dataset) was used to optimize analysis methods, while the remaining two-thirds (the replication dataset) were used for the reported study results.
referenceEngemann and Gramfort (2015) describe automated model selection in covariance estimation and spatial whitening of MEG and EEG signals in NeuroImage 108, 328–342.
procedureStatistical testing for MEG data was performed at the participant level, testing whether the correlation between data and theory-predicted models was greater than zero using Kendall’s tau, followed by a Mann–Whitney U rank test to compare theories.
procedureThe fMRI decoding strategy utilized a multivariate pattern analysis approach on the pattern of BOLD activity over voxels, similar to the strategy used for iEEG and MEG data.
procedureMEG decoding was performed on data that was bandpass-filtered between 1–40 Hz and downsampled to 100 Hz.
procedureIn the MEG analysis, single-trial covariance matrices were computed for vertices within the fusiform ROI identified from the FreeSurfer parcellation using the Desikan atlas, and trials exceeding 3 z-scores in Euclidean distance were excluded.
measurementFastICA was used to detect and remove cardiac and ocular components from MEG data, with an average of 2.90 components removed per participant (s.d. = 0.92).
measurementDecoding of face orientation was robust from MEG cortical time series in posterior regions of interest (approximately 75% with pseudotrial aggregation), but was weaker (35%) in prefrontal regions of interest.
procedureTo examine neural representation evolution, researchers performed cross-temporal representational similarity analysis (RSA) on source-level MEG data and iEEG high-gamma power within theory-defined regions of interest (ROIs).
accountFive participants were excluded from the MEG dataset: two for failing to meet predefined behavioral criteria (Hits < 80% or False Alarms > 20%), two for excessive sensor noise, and one for incorrect sensor reconstruction.
measurementMEG DFC analysis of task-irrelevant trials without removing the evoked response reveals significant content-selective synchrony between the face-selective GED filter node and both V1/V2 and PFC regions, characterized by an increase in low-frequency connectivity (< 25 Hz) and a decrease in high-frequency connectivity (25–100 Hz).
procedureFor MEG data analysis, researchers used source reconstructed data within predefined anatomical regions of interest (ROIs), which were bandpass filtered at 1–40 Hz and downsampled to 100 Hz.
referenceMaris and Oostenveld (2007) describe nonparametric statistical testing methods for EEG and MEG data.
measurementThe MEG sample in the study included 97 healthy participants with a mean age of 22.79 ± 3.59 years, consisting of 54 females and all right-handed individuals.
procedureThe study combined iEEG, MEG, and fMRI techniques to mitigate the limitations of using single data modalities, creating a cross-compensating approach for testing consciousness theories.
procedureResearchers computed Phase Locking Value (PPC) for each MEG time series–iEEG electrode pairing for face and object trials separately, using time-frequency analysis of broadband MEG and LFP signals via Morlet wavelets (f = 2–30 Hz in 1-Hz steps with 4 cycles; f = 30–180 Hz for iEEG or f = 30–100 Hz for MEG in 2-Hz steps).
procedureMEG trials were rejected if gradiometre values exceeded 5,000 fT cm−1, magnetometre values exceeded 5,000 fT, or if the trial contained muscle artefacts.
measurementMEG PPC analysis of task-irrelevant trials did not reveal any synchrony cluster in any region of interest after removing the evoked response.
procedureFunctional connectivity analysis (PPC) for both iEEG and MEG was computed between category-selective time series (face-selective and object-selective) and either V1/V2 or PFC time series.
measurementMagnetoencephalography (MEG) recordings showed selective synchronization between face-selective areas and both V1/V2 and prefrontal cortex (PFC) that was early, restricted to low frequencies (2–25 Hz), and mostly explained by stimulus-evoked responses, with Bayesian analysis supporting the null hypothesis for gamma-band synchronization (BF01 > 3).
referenceThe MEG-BIDS specification extends the Brain Imaging Data Structure to magnetoencephalography, as detailed in Niso et al., Sci. Data 5, 180110 (2018).
measurementMEG PPC analysis of task-irrelevant trials with a sample size of 65 reveals significant category-selective synchrony below 25 Hz for face-selective GED filters in both V1/V2 and PFC regions of interest, and for object-selective synchrony in the PFC region of interest only.
procedureFor magnetoencephalography (MEG) data, models were fitted to source data on predefined regions of interest (ROIs) using gamma (60–90 Hz) and alpha (8–13 Hz) bands as signals, analyzed separately for task-relevant and task-irrelevant conditions.
procedureFor MEG analysis, the researchers extracted reconstructed source-level data within predefined anatomical regions of interest (ROIs) based on the theories: GNWT ROIs included 'G_and_S_cingul-Ant', 'G_and_S_cingul-Mid-Ant', 'G_and_S_cingul-Mid-Post', 'G_front_middle', 'S_front_inf', and 'S_front_sup'; IIT ROIs included 'G_cuneus', 'G_oc-temp_lat-fusifor', 'G_oc-temp_med-Lingual', 'Pole_occipital', 'S_calcarine', and 'S_oc_sup_and_transversal'.
referenceMultivariate pattern analysis (MVPA) can be used to compare representational structures in time and space for MEG and EEG data.
procedureThe MEG and fMRI laboratories used the MEG-compatible and fMRI-compatible EyeLink 1000 Plus Eye-tracker system (SR Research) to collect data at 1,000 Hz.
measurementThe MEG data acquisition used a 306-sensor TRIUX MEGIN system, which consists of 204 planar gradiometres and 102 magnetometres arranged in a helmet-shaped array.
procedureMEG data were epoched into 3.5-second segments, consisting of 1 second pre-stimulus and 2.5 seconds post-stimulus onset.
measurementIn the study 'Adversarial testing of global neuronal workspace and integrated information theory', MEG cross-task decoding of stimulus categories (letters versus falsefonts) shows significantly above-chance (50%) decoding when classifiers are trained on relevant stimuli and tested on irrelevant stimuli (purple) or vice versa (orange), specifically within the posterior and prefrontal regions of interest.
claimThe observation that posterior brain areas peak earlier (0.1-0.2 s) than prefrontal areas (0.2-0.3 s) in MEG stimulus-evoked responses challenges the interpretation that decoding results are caused by signal leakage.
measurementMagnetoencephalography (MEG) recordings showed brief dynamic functional connectivity (DFC) in the alpha–beta frequency bands between face-selective nodes and both the prefrontal cortex (PFC) and V1/V2.
measurementIn the MEG leakage analysis (N = 32), stimulus-evoked response activity in posterior brain areas peaked between 0.1 and 0.2 seconds, whereas activity in prefrontal areas peaked later, between 0.2 and 0.3 seconds.
procedureFor MEG experiments, eye tracking data were acquired binocularly, while for fMRI experiments, data were acquired monocularly from either the left or the right eye in DCCN and Yale, respectively.
procedureMEG preprocessing involved sensor reconstruction using a semi-automatic detection algorithm and signal-space separation to reduce environmental artefacts.
procedureFor MEG analysis, category-selective single-trial time courses were extracted using the generalized eigenvalue decomposition (GED) method, where two GED spatial filters were built by contrasting faces or objects against all other categories during the first 0.5 s after stimulus onset.
claimGlobal Neuronal Workspace Theory (GNWT) faces a challenge regarding the representation of conscious experience contents, as the study found no representation of identity in the prefrontal cortex (PFC) and only limited representation of orientation in MEG, despite these dimensions being part of the participants' conscious experience.
procedureParticipants were required to have a minimum of 30 clean trials per condition to be included in the MEG analyses.
procedureHead position on the MEG system was monitored using four HPI coils placed on the EEG cap, positioned next to the left and right mastoids and over the left and right frontal areas, measured at the start and end of each run and before and after each resting period.
procedureThe MEG gantry was positioned at 68 degrees to ensure optimal coverage of both frontal and posterior brain areas.
procedureThe MEG data preprocessing pipeline used MNE-BIDS for conversion to BIDS format and the FLUX Pipeline in MNE-Python (v0.24.0) for processing.
measurementThe study utilized a sample of 29 iEEG patients for decoding analyses, with 576 electrodes in PFC regions of interest and 583 electrodes in posterior regions of interest, and further analyzed a population of 65 healthy participants using MEG.
measurementMEG and EEG data were bandpass filtered between 0.01 and 330 Hz and sampled at a rate of 1,000 Hz during acquisition.
measurementBayesian testing provided strong evidence against increased decoding accuracy when including prefrontal cortex ROIs for category decoding (face–object: iEEG BF01 = 1.94 × 10^4 and MEG BF01 = 3.05; letter–false font: iEEG BF01 = 1.91 × 10^5 and MEG BF01 = 4.70) and face orientation (iEEG BF01 = 1,205 and MEG BF01 = 3.26).
measurementIn the study, orientation decoding involved 160 front, 80 left, and 80 right trials per category for MEG, while iEEG used half these numbers.
Neuroimaging in psychedelic drug development: past, present, and ... nature.com Nature Sep 27, 2023 3 facts
claimNeuroscience studies on psychedelic drugs have primarily utilized functional Magnetic Resonance Imaging (fMRI), with ancillary research employing Magnetoencephalography (MEG) or Electroencephalography (EEG).
claimResearchers can utilize questionnaires from previous psychedelic drug trials, MEG, and EEG-based measures of neuroplasticity as supplementary tools alongside primary imaging techniques to study psychedelic drug effects.
claimStudies in psychedelic therapy rely on multimodal neuroimaging, specifically PET and MRI, combined with ancillary measures such as genotyping, subjective measures, pharmacokinetics, and EEG/MEG.
Practices, opportunities and challenges in the fusion of knowledge ... frontiersin.org Frontiers 3 facts
referenceMEG and LLM-KGMQA enhance knowledge graph-based question answering by integrating graph embeddings from a pre-trained knowledge graph encoder into a large language model and using the model's reasoning capabilities to refine query interpretations.
referenceCabello et al. (2024) introduced MEG, a framework for medical knowledge-augmented large language models for question answering, in arXiv preprint arXiv:2411.03883.
claimIn the medical domain, integrating knowledge graphs with large language models improves medical question answering by providing more accurate and contextually relevant answers to complex queries, as demonstrated by systems like MEG and LLM-KGMQA.
Adversarial testing of global neuronal workspace and integrated ... research.birmingham.ac.uk Oscar Ferrante, Urszula Gorska-Klimowska, Simon Henin, Rony Hirschhorn, Aya Khalaf, Alex Lepauvre, Ling Liu, David Richter, Yamil Vidal, Niccolò Bonacchi, Tanya Brown, Praveen Sripad, Marcelo Armendariz, Katarina Bendtz, Tara Ghafari Jun 5, 2025 2 facts
measurementThe study involved 256 human participants who viewed suprathreshold stimuli for variable durations while their neural activity was measured using functional magnetic resonance imaging (fMRI), magnetoencephalography (MEG), and intracranial electroencephalography (iEEG).
measurementThe adversarial study on consciousness theories involved 256 human participants who viewed suprathreshold stimuli for variable durations while their neural activity was recorded using functional magnetic resonance imaging (fMRI), magnetoencephalography (MEG), and intracranial electroencephalography (iEEG).
What a Contest of Consciousness Theories Really Proved quantamagazine.org Quanta Magazine Aug 24, 2023 2 facts
referenceMagnetoencephalography (MEG) tracks brain chatter but has poorer spatial resolution compared to functional magnetic resonance imaging (fMRI).
measurementThe adversarial collaboration experiment comparing Global Neuronal Workspace Theory and Integrated Information Theory involved six theory-neutral labs, 250 test subjects, and utilized fMRI, MEG, and intracranial electroencephalography.
Protocol for testing global neuronal workspace and integrated ... journals.plos.org PLOS ONE 2 facts
referenceThe paper 'FieldTrip: Open source software for advanced analysis of MEG, EEG, and invasive electrophysiological data' was published by Oostenveld R, Fries P, Maris E, and Schoffelen J-M in Computational Intelligence and Neuroscience in 2011 (Volume 2011, Article 156869, PMID 21253357).
procedureThe Cogitate research project tested predictions regarding consciousness theories in 250 subjects using fMRI, EEG, MEG, and implanted ECoG electrodes, employing several decoding analyses.
An adversarial collaboration to critically evaluate theories of ... biorxiv.org bioRxiv Jun 26, 2023 1 fact
measurementThe adversarial collaboration study on consciousness involved 256 human subjects who viewed suprathreshold stimuli for variable durations while neural activity was measured using functional magnetic resonance imaging (fMRI), magnetoencephalography (MEG), and electrocorticography (ECoG).
Adversarial testing of global neuronal workspace and integrated ... pubmed.ncbi.nlm.nih.gov PubMed 1 fact
procedureThe adversarial collaboration involved 256 human participants who viewed suprathreshold stimuli for variable durations while neural activity was recorded using functional magnetic resonance imaging (fMRI), magnetoencephalography (MEG), and intracranial electroencephalography (iEEG).
Adversarial testing of global neuronal workspace and integrated ... comdig.unam.mx Oscar Ferrante, Urszula Gorska-Klimowska, Simon Henin, Rony Hirschhorn, Aya Khalaf, Alex Lepauvre, Ling Liu, David Richter, Yamil Vidal, Niccolò Bonacchi, Tanya Brown, Praveen Sripad, Marcelo Armendariz, Katar May 5, 2025 1 fact
measurementThe Cogitate Consortium measured neural activity in 256 human participants using functional magnetic resonance imaging (fMRI), magnetoencephalography (MEG), and intracranial electroencephalography (iEEG) while participants viewed suprathreshold stimuli for variable durations.
Exploring “lucid sleep” and altered states of consciousness using ... philosophymindscience.org Philosophy and the Mind Sciences Jan 7, 2025 1 fact
referenceFieldTrip is an open-source software package designed for the advanced analysis of MEG, EEG, and invasive electrophysiological data, as described by Oostenveld, Fries, Maris, and Schoffelen (2011).
(PDF) Unifying Theories of Consciousness, Attention, and ... academia.edu Academia.edu 1 fact
claimNeuroimaging studies using EEG, MEG, and fMRI are uncovering distinct neuronal correlates of selective attention and consciousness in dissociative paradigms, suggesting a functional dissociation where attention acts as an analyzer and consciousness acts as a synthesizer.
Classification Schemes of Altered States of Consciousness - ORBi orbi.uliege.be ORBi 1 fact
claimSchartner et al. (2017) reported that psychoactive doses of ketamine, LSD, and psilocybin lead to increased spontaneous MEG (magnetoencephalography) signal diversity.
A Synergistic Workspace for Human Consciousness Revealed by ... elifesciences.org eLife 1 fact
claimTime-resolved extensions of the synergistic workspace framework, such as those developed by Varley and colleagues, may clarify the dynamics of the synergistic workspace when combined with high temporal resolution neuroimaging like magnetoencephalography or electroencephalography.
Rethinking Consciousness: When Science Puts Itself to the Test maxplanckneuroscience.org Max Planck Neuroscience May 14, 2025 1 fact
measurementThe Cogitate Consortium study involved 256 participants across seven laboratories worldwide, utilizing functional magnetic resonance imaging (fMRI), magnetoencephalography (MEG), and intracranial electroencephalography (iEEG).
Study Challenges Leading Theories On Consciousness Origins neurosciencenews.com Neuroscience News May 2, 2025 1 fact
procedureResearchers measured neural activity in participants using functional magnetic resonance imaging (fMRI), magnetoencephalography (MEG), and intracranial electroencephalography.