Vmrk File

[Kathrine Selvage]

BrainProductsGmbH provides technical and software solutions for neurophysiological and psychophysiological research and clinical applications. Their BrainAmp ExG amplifier allows to record signals with a sampling rate up to 5000 Hz and a broad hardware bandwidth ranging from DC to 1000 Hz.

BrainProducts also provides EEG caps with the electrodes distributed over the head according to the 1020 standard or to an equidistant scheme. Most of the caps provided by BrainProducts are actually fabricated by EasyCap, on whose website you can find more information. Although it is possible to use a BrainAmp amplifier with another type of cap, or to use an Easycap with an different amplifier, the most common case is to use them together and that is why we describe them jointly on this page.

The BrainVision Recorded and Analyzer software packages use a well-defined file format that is supported by many software packages (e.g., FieldTrip, EEGLAB, SPM, MNE-Python) and that is used in BIDS for EEG. The details of the BrainVision data format are available from the BrainProducts website.

Manually renaming BrainVision datasets may lead to errors, since the .vhdr and .vmrk file headers contain the name of the linked data file. Paul Czienskowski from the MPI for Human Development in Berlin, Germany, has written a small windows program that you can use: -renamer/. Or you can use this MATLAB function. When renaming a single or small number of datasets, you could also use a text editor to fix the header.

FieldTrip needs the user to define what file to read in. The BrainVision Recorder software usually stores different filetypes (.vhdr, .eeg, .vmrk). For reading the data into FieldTrip you can refer to the .eeg file, for example.

Sometimes users have already done some processing (e.g., rereferencing, epoching, artifact identification) in BrainVision Analyzer, and in order to avoid repeating the time consuming / subjective selection steps, it might be preferable to start from the processed data. BrainVision Analyzer stores the processing steps in a so called history file, keeping the raw data unchanged, and applying the processing steps on-the-fly. This is not something that FieldTrip can work with, so you need to export your data first.

When comparing your preprocessed data from FieldTrip to preprocessed data from BrainVision Analyzer, you might notice subtle differences. This might be due to two reasons: First, the filtersettings of BVA are hard to mimic using FieldTrip, because FieldTrip is using different defaults. Also, the order of preprocessing steps is fixed in FieldTrip, whereas you have to perform them manually, which makes it possible to do them in any order in BVA. The effect filters have on your data depend on the order of the preprocessing steps.

Examples regarding the type of plots can be observed here. In the template directory you can find a collection of template layouts for plotting. If you want to create your own custom layout files, please have a look here.

Dear Francois, we truly appreciate your prompt response. We are able to import the .eeg file into each subject. When we try to add the .vmrk file to be able to work with stimulus markers, we are unable to find it in the folder because in the file options, that extension does not show in the dropdown menu in Brainstorm. Could you please help us with the steps we should be taking before adding these two files? Thanks again for your help.

If you do not get anything new in your file, the format of the marker file might be slightly different than our functions are expecting.

If so, please zip those three files and send then to me (upload it somewhere, ie dropbox, then click on my username on this forum to then me the link in a separate email).

Note for BrainVision / BrainAmp users:

A bug was found in the application of the channel gain, the amplitudes read where sometimes incorrect.

Please update Brainstorm for reading correct amplitudes from the BrainVision files.

A follow up question on this topic on Brainvision markers and how they are read by Brainstorm. I understand the idea that only the .eeg file appears when trying to review raw files, but brainstorm reads the other two (.vmrk and .vhdr). Why is it that I cannot epoch the data using the markers read from those files, though?

When I click on "import data", the usual window is displayed with all the markers with [ext] in front of them. If I click in any of them, the option where we can specify the time window for our epochs becomes unavailable. That is, it seems as though I cannot specify the epoch length when using the markers that are automatically read from the .vmrk files.

When I click on "import data", the usual window is displayed with all the markers with [ext] in front of them. If I click in any of them, the option where we can specify the time window for our epochs becomes unavailable.

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