There may be several reasons. Have you checked the horizontal axis? I think the most simple problem could be that you are not looking to the correct time interval.

Asieh Daneshi, thanks a lot for your suggestion. Unfortunately, that is the case for the whole plot.

Could you send a small part of your data here? Just one channel, or a small time interval?

This way I can figure out the problem better :-)

Hi Sylwia Kaduk

I will suggest you go to the figure properties to check if your imported EEG data in MATLAB is appearing in XTick, YTick sections over there. If it is appearing there, then as suggested by Asieh Daneshi , you need to check if you are viewing that figure for correct axis values.

Dear Asieh Daneshi Prasanna Raut, I attach a snip of my database. It's a matlab numeric matrix with EEG for one participant. Each column is a channel, and it has 2720332 rows with a sampling rate of 500 SPS. I'm not very experienced with EEGLab so I thought that maybe the data format is the reason. However, EEGLab was able to automatically identify 20 channels, so at least that worked.

I wanted to check your data on my own system, but it is a png file and I can't do that. So, my suggestion is that change your y axis scale. As @Prasanna Raut recommended, you can plot your data outside eeglab with a simple plot command to see if the problem is with your eeglab or not

Dear Asieh Daneshi , sorry I misunderstood you. That would be really great if you could check if file works for you. I attach a small part of my EEG file, it is in a matlab numeric matrix. It contains all 20 channels, but only 22 rows, that gives 44 milliseconds of the recording. I choose such a small piece to keep file light enough for easy transfer.

Okay, good. Now I know the problem. just do this: in scroll channel screen, choose "Display", then "remove DC offset"

:)

Dear Asieh Daneshi , that completely solved my problem. You have no idea how grateful I am! All the best