Hi,
I’m a new user of Brainstorm and in despite of my researchs I could’nt find a solution. I’m sorry if I missed a post where it is explained.
There is a scale error between the signal in BrainVisionAnalyzer and the data exports in Brainstorm.
The data were exported from BrainVisionAnalyzer according to these parameters :
*** Generic Data Export ***
File name parameter: $h_$n
File extension: .eeg
Write header file: yes
Write marker file: yes
Format: BINARY
Orientation: MULTIPLEXED
Line Delimiter: CRLF (PC style)
Binary format: 16-Bit signed integer format
Set resolution manually: no
Individually optimized resolution for each channel: no
Convert to big-endian order: no
Export all channels: yes
Data were imported in Brainstorm by using import MEG/EEG : EEG: BrainVision BrainAmp (*.eeg). The DC offset wasn’t chosen as an option.
The data are already preprocessed, epoched and averaged (we imported the averages of our protocol).
The unit of the scale is in microvolts in BrainVisionAnalyzer and milivolts in Brainstorm. Moreover, the differences between the two scale don’t seem to follow a whole multiplying factor.
I join you a screenshot with the both logiciel for the same subject, condition and channel.
I hope you can help me with this problem.
Thank you a lot in advance,
M.
Hello,
It’s possible that there is some scaling information that is not read correctly from the BrainVision header (the .vhdr or .ahdr file).
Could you send me an example file so I can look at it?
Upload the file somewhere (eg dropbox) then send me the link in a separate email (click on my username on this forum).
Thanks,
Francois
Hi
I apologize for the delay of my answer. I searched a secure way to send you the file with the lab but we have some means only when it concerns files’ transmission with other french universities.
I can’t use dropbox because mine is already full and I can’t clear it. I propose you to use google drive if it’s possible.
I don’t really understand why it would be a problem with the header because I did’nt import them in Brainstorm. I’ll be very please to understand this point and then how Brainstorm is running.
Thanks a lot for your quieckly reply.
M.
Hello,
One dataset in the BrainVision format consists in multiple files that must stay in the same folder (.vhdr + .eeg + .vmrk).
They are all imported at once in Brainstorm, the .vhdr information contains the information on how to read the .eeg file.
Send me a full dataset (including the .eeg and .vmrk) if you want me to look at it, I can’t do much just with the header.
Francois
Hi,
I sent you an email with the download links for the two missing files (eeg and vmrk).
I better understand the functionning of Brainstorm. It was logic but I wanted to be sure. The files are in the same folder on the computer.
Thanks again for your time, it is very helpfull.
M.
Hello,
Looking at your files made me realize that the gain of the channels was not read properly.
In your file, this correspond to the value in the channel definition line, for example: "Ch4=E1,0.00014933234,"
This factor 0.00014933234 has to be multiplied with the values read from the file, and this was not done correctly.
I fixed it, now the display in Brainstorm looks like your Analyzer window.
Update Brainstorm and try again (menu Help > Update Brainstorm)
Thanks a lot for reporting this! This was a very important bug to fix!
Francois
Hi,
I’m glad that this problem could help to fix a bug !
Thanks a lot for your patience and your help !
M.
Hi,
I’m really sorry but the problem isn’t fixed. I had to wait to do the update because it requires administrator rights. And now, I realise that the problem persists.
Brainstorm is updated and I restart the computer to be sure.
Thanks in advance,
M.
Are you using the compiled version of Brainstorm?
I haven’t updated the compiled version, will do later today.
I’ve just posted the new updates.
Please update Brainstorm and try again.
Hi,
We are using the compiled version and after I saw your post I did the good update.
I’m sorry for the delay of my response, I wasn’t at the lab at the end of the last week.
However the problem persists.
Thanks for your time,
M.
Hello,
I didn’t make it clear you had to delete your links and re-create them, in order to get correct amplitudes.
The gains are saved in the “Link to raw file”, this has to be generated again.
The current compiled version of Brainstorm gives exactly the amplitude ranges you were showing in your initial screen capture.
See the my edit of your screen capture below.
Francois
Hi,
I’m sorry for the delay of my response, I had to deal with some analysis problems.
It is working, thanks a lot !
M.