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Purpose

OMEGA is amongst the largest repository of MEG data presently available. It is a continuously expanding resource that also contains anatomical MRI volumes, demographic and questionnaire information. OMEGA may also feature multimodal electrophysiological data (e.g., EEG, field and cell recordings).

The primary objective of OMEGA is the conservation of brain imaging data collected with different brain imaging techniques and behavioral tests scores from healthy and patient volunteers (any age range), in order to allow future research in the field of high-powered detection of effects of interest in human brain activity.

OMEGA in a resource to establish typical features of brain activity, in relation to demographic factors (age, gender, standardized behavioral tests scores, etc.) and to reveal new markers of abnormal brain activity in various pathologies.

We hope OMEGA contributes to open scientific research, for the advancement of knowledge, and the greater good.

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Highlights

• First open data repository fully dedicated to MEG.
• MEG data from 644 participants (see details below): 444 healthy controls and 200 patient volunteers (Parkinson, ADHD, chronic pain). About 1800 resting-state MEG recordings totalling over 150 hours of data.
• Structured according to the (v1.10.0).
• Directly readable by data-analysis software like .
• Anatomical T1-weighted MRI volumes (defaced) of most participants.
• Demographic and standardized questionnaire data.

Participants

Group	Sex	18 -	20 -	30 -	40 -	50 -	60 -	70 -	80+	Tot
Control	F	12	109	23	9	14	78	26	2	273
Ìý	M	12	83	19	7	3	33	12	2	171
Parkinson	F	Ìý	Ìý	Ìý	2	16	12	13	3	46
Ìý	M	Ìý	Ìý	Ìý	8	23	50	31	3	115
ADHD	F	4	7	2	Ìý	Ìý	Ìý	Ìý	Ìý	13
Ìý	M	4	4	Ìý	Ìý	Ìý	Ìý	Ìý	Ìý	8
Chronic Pain	F	Ìý	Ìý	1	1	3	2	1	Ìý	9
Ìý	M	Ìý	Ìý	Ìý	3	5	1	Ìý	Ìý	9
Total	Ìý	32	203	45	30	64	176	83	10	644

Current version

The present version is Release 3.1.0: it re-introduces most participants shared previously, as well as more new data from recent studies, totalling over 600 participants!

Coming soon

• Manual co-registration of MEG & MRI for over 200 subjects, including PD and AD studies
• Partial medication list for PD patients
• Sleep data

Access

OMEGA promotes open-science good practices via, presently, a controlled access procedure.

You will need to provide your full name, affiliation, and a valid institutional email address (Gmail, Yahoo, iCloud, etc. addresses are not permitted). This information is for verification and curation purposes only, and will not be used outside of OMEGA.

You are also asked to review and accept the following terms of the OMEGA Data Use Agreement:

• You must agree to respect the data privacy standards in effect in Quebec and Canada. In particular, you must not attempt re-identification of participants nor redistribute the data. Please redirect any request to access your copy of OMEGA to the present page.
• You must acknowledge that the proposed study has been reviewed and approved by the duly constituted research ethics board(s) that has/have jurisdiction over it – typically the IRB/REB from your home institution. However, if the project originates from a jurisdiction where ethics approval is not required, you must seek and have obtained approval from , and provide the approved REB study number at the time of your registration to OMEGA.

• You will need to keep the retrieved OMEGA data in a secure environment. You shall not share this copy or use it to create a new bank or repository.
• You will recognize the contribution of OMEGA in all your publications and presentations of study work or results obtained using data from OMEGA.

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Please click here to register.

Data

Retrieving data

The data is stored on a secure ownCloud instance at the BIC. is an open-source web-based file hosting application similar to Dropbox or Google Drive. Once you have been granted access, you will receive access credentials by email. You can then download files via the following options. Additional configuration details are available on the .

1. is simple, but not the most efficient for downloading large volumes of data at once.
2. is more complex to set up, depending on the OS, but is a versatile option. It allows mounting the shared directory and copying files with common file managers (e.g., Windows Explorer, Mac OS X Finder, Linux KDE Dolphin) or from the command line. You may try a WebDAV client (e.g., or ) to help with the setup and provide a user-friendly interface to retrieve files. It is also possible to download directly from the command line, e.g. in an HPC environment, with tools like wget, curl, or rclone.
3. is designed to synchronize files between a local computer and an ownCloud server. It can be used by guests to download shared files.

Data organization

OMEGA is structured according to 1.10.0.

Apart from some general files in the root folder (dataset_description.json, participants.tsv, CHANGES, LICENSE, etc.), and the demographic information in the phenotype subfolder, the imaging data is organized by participant, session and modality, as the following example:

sub-0000/
ÌýÌýÌýÌýses-01/
ÌýÌýÌýÌýÌýÌýÌýÌýsub-0000_ses-01_scans.tsv
ÌýÌýÌýÌýÌýÌýÌýÌýanat/
Ìý Ìý Ìý Ìý Ìý Ìý sub-0000_ses-01_T1w.nii.gz
ÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýsub-0000_ses-01_T1w.json
ÌýÌýÌýÌýÌýÌýÌýÌýmeg/
ÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌý sub-0000_ses-01_task-noise_run-01_meg.ds
ÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýsub-0000_ses-01_task-noise_run-01_meg.json
ÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýsub-0000_ses-01_task-noise_run-01_channels.tsv
ÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌý sub-0000_ses-01_task-rest_run-01_meg.ds
ÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌý sub-0000_ses-01_task-rest_run-01_meg.json
ÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌý sub-0000_ses-01_task-rest_run-01_channels.tsv
Ìý Ìý Ìý Ìý Ìý Ìý sub-0000_ses-01_task-restaftertask_run-05_meg.ds
Ìý Ìý Ìý Ìý Ìý Ìý sub-0000_ses-01_task-restaftertask_run-05_meg.json
Ìý Ìý Ìý Ìý Ìý Ìý sub-0000_ses-01_task-restaftertask_run-05_channels.tsv
Ìý Ìý Ìý Ìý Ìý Ìý sub-0000_ses-01_coordsystem.json
Ìý Ìý Ìý Ìý Ìý Ìý sub-0000_ses-01_headshape.pos

In each session folder, a _scans.tsv table lists the MRI scans and MEG recordings available.

MEG data

OMEGA contains data collected as part of many different studies. A few of the larger projects collect additional data such as clinical info, neuropsychological tests, imaging, genetics, etc. that are shared in separate repositories. In these cases, participant IDs in OMEGA match the IDs in the other repositories, or a key for matching IDs can be provided upon request. This is currently the case for these two projects:

• Ìý(Pre-symptomatic Evaluation of Experimental or Novel Treatments for Alzheimer's Disease)
  Participant ID:Ìýsub-CONP0000 (119 participants)
  Access:ÌýÌý
• Ìý& Canadian Open Parkinson Network Database; and
  The Neuro Open Biobank (aka Clinical Biospecimen Imaging and GeneticÌýRepository, C-BIG)
  Participant ID: sub-PD0000 and sub-MNI0000 (157 participants)
  Access:ÌýÌý& ,Ìý

Currently, OMEGA only contains resting-state MEG recordings. Task recordings may be added in future releases. "Baseline" rest recordings are identified by the task label "rest". If a rest recording was collected after the participants performed a task, the label is "restaftertask".

Empty-room "noise" MEG recordings were collected for most MEG sessions and are included in each session folder, next to the participant's recordings.

The data were all performed with the 275-channel 2005 series system at the McConnell Brain Imaging Center.

Raw MEG data files were renamed, de-identified and structured according to BIDS with custom MATLAB code, some of which is available in our (2024-10-10).

When system issues, environmental noise, or participant-specific artefacts (e.g., dental work or makeup) were noted by the individual acquiring the data, this information is saved in the _meg.json file, in the SubjectArtefactDescription field. We will update this information as it is reported by users or identified by improved quality control procedures.

Most recordings are resting state in sitting position, with eyes open, and with EOG and ECG electrodes. However a few studies had slightly different setups. While this information can be found in the files of each recording, these special cases are also listed in the README.md file for convenience.

MRI data

One or more T1w MRI images are included for each participant, when possible, for source imaging purposes.

Raw DICOM images were sorted, de-identified and converted to the NIfTI-1 file format and BIDS structure with (0.10.0). Images were then de-faced (facial features replaced by a template to further preserve anonymity) with (0.3.3).

Co-registration

Since the anatomical images are de-faced, we aim to soon provide co-registration information in the form of matching anatomical fiducial point coordinates in the AnatomicalLandmarkCoordinates field of the MRI _T1w.json file and the MEG _coordsystem.json file. We will do this rigorously, using the MRI image, digitised head shape and fiducial points, and pictures of MEG head coil placement, as appropriate given the availability and quality of these data for each subject.

In the meantime, the suggested approach is to use the head points to do the alignment as described in the , excluding points in the "defaced" area. This should be accurate within a few mm to a cm in most cases, but not as accurate as it would be with manual verification and correction. We found that this automatic registration often leads to unsatisfactory positions of the fiducial points on the head surface based on our practice and on pictures of the MEG head coils on the participant. Thus we are investigating the issue and we are working to manually verify and align each participant. About half have been completed.

Note that once this manual co-registration is provided, the head coil coordinates saved in the MEG json files may no longer correspond exactly to the digitised head coil coordinates present in the _headshape.pos file.

Scan dates

As an additional anonymization measure, session dates were shifted by a fixed number of days within each participant volume (the shifting procedure sets the first sessions for each participant to 2000-01-01.) Hence, the relative date difference between sessions for each participant remains meaningful. These relative times can also be obtained with the (fractional) age provided in the sessions table (see demographics section below).

OMEGA general questionnaire

The questionnaire administered to participants evolved over time, therefore the available data varies between subjects. General information such as age, gender, sex, handedness, etc. is available for the bast majority of participants. All questionnaire versions are now combined in a single table.

Some responses from previous versions were recorded in French and still appear as such in the table. We aim to translate most answers in an upcoming release.

The questionnaire is primarily a collection of brief standardized tests. It is described in detail in the file phenotype/OmegaQuestionnaireDescription.pdf, and the questions themselves are provided in the accompanying json files (English and French).

Participant demographics

Basic participant information is provided in the file participants.tsv. As some volunteers participated in multiple studies and their age or category may change between sessions, an additional table is provided with per-session values: phenotype/sessions.tsv. The age and category in the participants table correspond to the first MEG session for each participant.

Contact

For any inquiry, please contact , OMEGA Principal Investigator, at sylvain.baillet [at] mcgill.ca ()