Annotations of bad segments of MEG/EEG/iEEG data

[wmvanvliet]

The BIDS specification for EEG/MEG/iEEG data allows for the specification of "bad channels", but how about bad segments? Bad segments are segments were all channels are bad, for example due to some issue with the recording hardware, or two raw files were concatenated, causing a "jump" in the signal. This is valuable information to have alongside the raw data, because most processing algorithms will need to skip these sections in order to function properly. Is there a way to encode this information in the BIDS standard?

[sappelhoff]

Hi @wmvanvliet!

annotations are currently not part of the specification for raw MEEG data ... however, we have an ongoing discussion about this in BEP021 about electrophysiology derivatives: https://bids.neuroimaging.io/bep021

feel free to chime in :-)

[wmvanvliet]

It's good that we can have them somewhere. However, I don't see annotations as being "derivates" from the data. When they are manual annotations, they are raw data. Section 3 of the derivatives proposal does a great job of specifying how they could be encoded in the BIDS format. This section should be merged in the main BIDS specification!

[jadesjardins]

Hi @wmvanvliet, I agree that we should work towards merging annotations into the main BIDS specification. I have been working with annotations so far in the context of a derivative state of EEG data (e.g. https://github.com/BUCANL/bids-examples/tree/BEP021_face13/eeg_face13)... However the annotations themselves are not a new state of the data but rather a set of appended properties (contained within formatted files) that are just as likely to belong to the raw data at the root of a BIDS project.

[dorahermes]

This is being addressed using HED tags for artifacts, an example is under review in the BIDS examples pull request #324: bids-standard/bids-examples#324