Hi all, I came across a weird artifact in my MEG data (Neuromag Vectorview). Not sure how to describe it or what is going on. So, here a screenshot of what it looks like: [image] The data is unprocessed at that stage. The artifact is only sometimes present in the file, and also only over some se…

Hello, I don’t know about the artifact, but the error during writing is apparently due to an invalid value in raw.info['subject_info']['weight'], which is currently set to 'n/a', but must be a float (or, I suppose, None if not available): [image] eort: -> 2146 write_float(fid, FIFF.FIFF_SUBJ…

Hi Eduard, We also work with Neuromag MEG data, and we have seen a similar kind of issue with data processed through maxfilter to do movement compensation. If there are time gaps without accurate cHPI (continuous head position indicator) signal, and you’ve chosen the -movecomp without “inter” opti…

Hi Megan, Thanks for your input! Indeed the data are really unprocessed, we have not even recorded cHPI, so that is probably not the reason for this artifact. But it sounds possible that running tSSS (without movement compensation), could cause the issue that leads to the error when trying to save …

[image] eort: But it sounds possible that running tSSS (without movement compensation), could cause the issue that leads to the error when trying to save the file, in line with @richard ’s comment. Are you saying that a read-write roundtrip works if you don’t process the data; but once you app…

Could you confirm that you did not, in fact, manually touch info? Yes, that I can do. Definitely haven’t touch the info. Are you saying that a read-write roundtrip works if you don’t process the data; but once you apply tSSS, saving fails because of the invalid value in info? That I thought, …

Mini update, on that issue. The saving issue is not due to tSSS or any other noise in the data. Instead it seems to be related to the BIDS-conversion of the data. The height field in subject_info that raw.save is complaining about, originates in the participants.tsv that mne-bids read out during th…

Thanks, that is obviously a bug in MNE-BIDS then, storing invalid data in info upon reading. Can you create an issue on the MNE-BIDS GitHub repository?

Great, the read/write problem was fixed here (reason being participants.tsv containing None’s). Thanks! The issue with the artifacts remains though (it is unrelated to the bug). So if anyone has some ideas, I’d be happy to here! Eduard

in your original image, I count 20 y-axis labels (channels) and 20 normal-looking traces, the straight-line rays seem to be in addition to the normal traces. Can you try plotting this file after running mne.set_browser_backend('matplotlib')? That might narrow down whether the problem is in the fil…

You’re absolutely right @drammock . Plotting with the matplotlib backend looks fine. [image] So, it seems to be a plotting artifact, and the data should be fine, right? Do you need the file to find what is causing the issues with the plotting? Thanks, Eduard

Strange Artifact with Neuromag MEG data

Support & Discussions

eort August 5, 2022, 4:31am 16

For the record, the plotting problem was present only for mne 0.24. Updating to 1.x solved the issue.

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Strange Artifact with Neuromag MEG data

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