What’s new?

Version 0.19 (unreleased)

👩🏽‍💻 Authors

The following authors contributed for the first time. Thank you so much! 🤩

• None yet

The following authors had contributed before. Thank you for sticking around! 🤘

• Bruno Aristimunha

• Pierre Guetschel

• Alexandre Gramfort

• Marijn van Vliet

Detailed list of changes

🚀 Enhancements

• Add support for reading and writing MEF3 (Multiscale Electrophysiology Format) iEEG data with the .mefd extension. Requires MNE-Python 1.12 or later, by Bruno Aristimunha (#1511)

• Save Annotations.extras fields in events.tsv files when writing events, by Pierre Guetschel (#1502)

• Added support for EEGLAB and EEGLAB-HJ coordinate systems as defined in the BIDS specification. Both use ALS orientation (identical to CTF) and map to MNE’s ctf_head coordinate frame, by Bruno Aristimunha (#1514)

• mne_bids.read_raw_bids() now reads channel units from channels.tsv and sets them on the raw object. This includes support for units like rad (radians), V, µV, mV, T, T/m, S, oC, M, and px. The write path was also updated to correctly write rad units to channels.tsv, by Alexandre Gramfort (#1509)

• Added support for hashing BIDSPath objects so they can be used in caching and other contexts that require hashable objects, by Eric Larson (#1563)

• Speed up mne_bids.get_datatypes() by restricting filesystem traversal to bids_root/sub-*/(ses-*/)<datatype> directories, by Eric Larson (#1563)

• Speed up mne_bids.BIDSPath.find_matching_sidecar() by searching most likely file locations first, by Eric Larson (#1565)

• Add support for CHPI channels and gracefully handle incorrect channel definition MEGGRAD, by Eric Larson (#1578)

• Add keywords parameter to mne_bids.make_dataset_description() for the BIDS Keywords field, by Bruno Aristimunha (#1602)

🧐 API and behavior changes

• Expected format conversions notices are now logged at info instead of warn level, by Bruno Aristimunha (#1589)

• Add readme parameter to mne_bids.write_raw_bids(); pass readme=False to leave any existing README untouched and skip creating one, by Bruno Aristimunha (#1550)

• mne_bids.make_dataset_description() preserves BIDS-spec keys it does not model when merging with an existing dataset_description.json, by Bruno Aristimunha (#1548)

🛠 Requirements

• MEF3 (.mefd) file format support requires MNE-Python 1.12 or later, by Bruno Aristimunha (#1511)

🪲 Bug fixes

• Fix mne_bids.BIDSPath.find_matching_sidecar() to search for sidecar files at the dataset root level per the BIDS inheritance principle, by Bruno Aristimunha (#1508)

• Reinstate the requirement for coordsystem.json whenever electrodes.tsv is present (including EMG), by Bruno Aristimunha (#1508)

• Fix read_raw_bids() ignoring electrodes.tsv when EEGCoordinateUnits is "n/a" by inferring the unit from coordinate magnitudes, and synthesize approximate fiducials for ctf_head montages to enable the coordinate transform to head frame, by Bruno Aristimunha (#1506)

• Improve mne_bids.read_raw_bids() handling when electrodes.tsv exists without coordsystem.json: emit a warning and continue without applying a montage (previously raised for iEEG), by Bruno Aristimunha

• Allow task=None in mne_bids.read_raw_bids() for BIDS paths without a task entity (e.g. datasets that omit task in the path), by Aman Jaiswal

• Fix mne_bids.read_raw_bids() and related read paths failing with PermissionError on datalad/git-annex datasets by keeping the file lock next to the symlink instead of its (read-only) target, and gracefully continuing without a lock when one cannot be created, by Bruno Aristimunha (#1569)

• Avoid modifying calibration files by making mne_bids.write_meg_calibration() copy instead of parsing and rewriting, by Marijn van Vliet (#1576)

• Fix bug with mne_bids.BIDSPath.find_matching_sidecar() not searching parent directories properly, by Eric Larson (#1565)

• Detect TSV file encoding before reading, fixing UnicodeDecodeError on non-UTF-8 sidecars (e.g. channels.tsv with µV in latin-1), by Bruno Aristimunha (#1593)

• Fix mne_bids.events_file_to_annotation_kwargs() to drop rows with invalid onset values (n/a, nan, NaN, empty string) before float conversion. This makes reading real-world OpenNeuro datasets (e.g. ds004841, ds004842, ds004843) succeed instead of either raising or returning NaN onsets, by Bruno Aristimunha (#1547)

• Fix mne_bids.events_file_to_annotation_kwargs() to fall back to the value column when trial_type is entirely n/a but value contains trigger codes, instead of dropping all events, by Bruno Aristimunha (#947)

• mne_bids.read_raw_bids() now tolerates malformed scans.tsv entries and ISO 8601 acq_time variants, by Bruno Aristimunha (#1591)

• mne_bids.read_raw_bids() is more tolerant of imperfect channels.tsv files and supports a new on_ch_mismatch="warn" option, by Bruno Aristimunha (#1603)

• Allow non-numeric run entities (e.g. run-5H) in mne_bids.BIDSPath when check=False, by Bruno Aristimunha (#1601)

• mne_bids.write_raw_bids() now writes an *_electrodes.json sidecar so derivative datasets pass the BIDS validator, by Bruno Aristimunha (#1545)

• mne_bids.read_raw_bids() now strips whitespace-padded n/a cells and normalizes European-locale decimal commas in TSV sidecars, by Bruno Aristimunha (#1599)

• mne_bids.read_raw_bids() now warns (instead of raising ValueError) when participants.tsv exists but does not list the requested subject, leaving raw.info["subject_info"] empty. This unifies behavior with the existing missing-participants.tsv path, by Bruno Aristimunha (#1606)

⚕️ Code health

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