User Tutorial:Designing an Eloc File

The BCI2000 Offline Analysis tool generates up to three different types of plots to aid you in determining the best features in a given dataset. One of these plot types - the topographic plot - provides a spatial representation of the subjects response to a given stimulus. So, when generating such a plot, the electrode layout must be taken into account. To communicate this layout to the BCI2000 Offline Analysis tool, we use a montage file. This section of the tutorial will show you how to use the Eloc Helper tool to create and modify montage files.

Creating a new montage file

First, let's create a new ECoG montage file:

1. Open the Eloc Helper tool. If this is your first time using the tool, you may want to briefly review User Reference:Eloc Helper for instructions on how to install and run this application.
2. Click File>New>ECoG Montage File to start working on a new ECoG montage file. Since ECoGs are taken using an electrode grid, you will be given a square electrode map.
3. Create your first electrode:
   1. Click the "Create New" button.
   2. Set the coordinates by clicking the "Use Grid" button and then clicking on the blank electrode map.
   3. Click the "Update" button after which you should see an electrode marker appear in the location you clicked on in the previous step. Notice that the marker is labeled with the number "1" (i.e., the value that was set automatically for the number property of the electrode) and that the electrode list has a new item "1: elec" consisting of the electrode number and label. Try changing the number and label to something else and clicking "Update." Keep in mind that the number must be a strictly positive integer (i.e., 1, 2, 3...) and that the label must be no more than 4 characters.

For the montage files we need to create to work with the data in this tutorial, it is much more convenient to start from an existing file.

Modifying an existing montage file

1. Click File>Import>EEG Montage File.
2. Since we added a new electrode in the previous section, you will be asked if it's okay to overwrite all the current entries. Click "Yes".
3. In the "Choose a montage file" file browser, navigate to data/samplefiles and double-click or otherwise open the "eeg58.loc" file.