Difference in ERP amplitude between SPM and brainstorm

1

Hi François,

The screenshot attached shows an ERP in SPM and in Brainstorm (where I did all the pre-processing and epoching and then imported my data in SPM) in 2 conditions for one subject.

Capture d’écran 2022-11-03 à 17.24.32
Capture d’écran 2022-11-03 à 17.24.32730×635 174 KB

The shapes are very similar in the two software, but the amplitude of the signal seem to differ differently according to the time, which is quite weird. For example, in the first condition, the second peak is higher than the first peak in SPM but not in brainstorm while the third peak seems smaller than the second peak in SPM but not in brainstorm.

Do you know what happens? (I am not sure I should ask this here or on the SPM list, so I did both)

Best.

2

For the Brainstorm side: make sure you do not have any montage or filter applied for visualization.
The kind of changes you obtain look like there is maybe an average reference added in the Brainstorm figures.
These visualization parameters are not saved on the hard drive and not applied when exporting the file to another format.

If you doubt of the display or the contents of the file: load the .mat file and plot it directly with Matlab.

3

Hi François,

Thank you for your answer. The problem came from the SPM side finally (detrend settings).
best,

Adeline