Montage editor [Under construction]

Authors: Francois Tadel

The display of the time series figures can be configured using montages of sensors. The term montage in the Brainstorm interface can refer to a simple sub-selection of data channels, or a linear recombination of these channels (eg. average reference or other EEG re-referecing montage). The selection of channels was already introduced in the tutorials Continuous recordings and EEG and epilepsy. This page illustrates how to use the montage editor to create custom displays.

Pre-defined montages

The interface offers a few pre-defined montages for standard acquisition systems for MEG (Elekta-Neuromag, CTF, Yokogawa, 4D) and EEG (10-20 and 10-10 caps). The montage menu is accessible from the Record tab or with the popup menu on the time series figures.

Let's switch to a nicer representation of the recordings time series: click on the "Display mode" button in the toolbar of the Record tab.

Now the traces are displayed in columns, but all the channels are displayed in the same figure, which makes it unreadable. Select a subset of channels by right-clicking on the figure > Montages, with the drop-down menu in the Record tab or with a keyboard shortcut (Shift+A, B, C...). Default groups of sensors are available for some MEG systems, but you can also create your own groups of sensors with the menu "Edit montages".

Montages

A better way to review a large number of MEG/EEG signals at once is to display only a subset of them at once. This can be done using the "montage" interface. The term refers mainly to EEG, to define the referencing system used to display the values recorded on the electrodes: bipolar montages, custom reference electrodes, average reference. However, the same interface can be used in MEG to select only a subset of sensors in a given figure, using a predefined or custom set of channels.

• Use the drop-down menu in the Record tab to several predefined sets (ex. CTF LF = Group of left frontal sensors). Alternatively, right-click on the figure > Montage. You may need to decrease again the gain of the channels (use SHIFT+Mouse wheel)

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• Note the keyboard shortcuts: SHIFT+letter. It makes it really easy to switch from a group of sensors to another (ex: Shift+A = all sensors, Shift+B = Left-frontal, Shift+C=Right-frontal...)

• To edit/create your own selections, use the menu "Edit montages". You can edit the channels selection groups or the electrodes montages available for this installation of Brainstorm. By default, it shows only the ones that are relevant to the type of recordings you are currently looking at (in this case: CTF MEG recordings). To see all the available options, click on the button "All".
• Click on "New channel selection" to create a new selection Test1, and select a few channels in the list.

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• Click on Save. Back to the time series figure. Look in the popup menu again, you can see your new selection in the menu: Test1. You can now use the time series view with these predefined selections of sensors.
• To display several montages at the same time, or with different different display options, you need to open twice the same file and then set the parameters differently. You have two option to clone the figure:

  • Do twice: Right-click on the file in the database explorer > MEG > Display time series

  • Right-click on a figure > Figure > Clone figure

  • To have the same scale in both figures, use the buttons "..." in the figures

    

Apply a montage to the recordings

The montage selection is only a visualization option, it never modifies the recordings. If you want to apply a specific montage to the recordings, you need to call the process Standardize > Re-reference EEG (see EEG and Epilepsy) or the process Standardize > Apply montage (only available for imported epochs).

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