Tutorial 17: Visual exploration

Authors: Francois Tadel, Elizabeth Bock, Sylvain Baillet

This tutorial illustrates the options Brainstorm offers to represent graphically and explore interactively the evoked responses we computed in the previous tutorial. It shows how to produce spatial maps of the sensors, temporal averages, save screen captures and movies.

2D/3D topography

The sensor values at one time instant can be represented on a surface. Each amplitude value gets associated with a color using a colormap (described in the next tutorial). We call this type of representation "sensor topography", it shows the spatial distribution of the magnetic fields (or electric potentials).


Magnetic interpolation

By default, some of the views re-interpolate the fields that are recorded by the MEG sensors to get smoother displays. A simple inverse problem and forward problem are solved to reconstruct the magnetic fields on a high-resolution surface of virtual magnetometers (function channel_extrapm.m).

On Elekta-Neuromag systems, this interpolation has the effect of converting the topographies of the planar gradiometers into topographies of magnetometers, which deeply affects the display.

The menu "No magnetic interpolation" offers the same views, but without using this reconstruction of the magnetic field. A spatial interpolation of the values between the sensors is performed instead.


2D Layout

The menu 2D Layout represents, in the same figure, the spatial information (the values for each channel is represented where the sensor is actually located) and the temporal information (instead of just one single value, we represent the signal around the current time).
The light gray lines represent the zero amplitude (horizontal) and the current time (vertical lines).

To zoom in/out in each small graph, use the buttons at the bottom-right corner of the figure, or the corrsponding mouse shortcuts: Ctrl+mouse wheel and Shift+mouse wheel. To select multiple sensors simultaneously: right-click and move your mouse to enlarge the selection rectangle.

You can use this display mode to compare multiple files:
Select multiple files in the database explorer, right-click on any of them > 2DLayout.


Display as image

The menu "Display as image" shows the same information as the "time series" view, but the values for each sensor are represented with a color instead of a line.


Time selection

Click somewhere on the white part of the time series figure, hold the mouse button, and drag your mouse left or right: A transparent blue rectangle appears to represent the time selection. If you right-click on the figure, new options become available in the popup menu:



Using Brainstorm, you will quickly feel like saving the beautiful images you produce. Your operating system already provides some nice tools for doing this. Many other options are available in the "Snapshot" menu, accessible with a right-click on any Brainstorm figure.

Operating system

Snapshot menu


Movie studio


Contact sheets

A contact sheet is a large image representing many time frames of the same figure.


Edit the figures

All the figures can be edited with the Figure popup menu:

If you select both "Matlab controls" and "Plot edit toolbar", you will get all the tools available in the Matlab environment to explore the data and edit the figure. Select the button "Edit plot" to edit the graphic properties of an object (eg. select a signal, then right-click on it to edit its properties) or unselect it to get back to the regular Brainstorm figure interactivity.


Mouse shortcuts



Click on something


Keyboard shortcuts

Here is a memo of all the keyboard shortcuts for time series and topography figures. If you don't remember them, you can find most of them in the figure popup menus.


Graphic bugs

If you observe any graphic problem with these displays, there might be an issue with the OpenGL drivers. You may try the following options.

Feedback: Comments, bug reports, suggestions, questions
Email address (if you expect an answer):

Tutorials/ExploreRecordings (last edited 2019-03-14 23:59:12 by FrancoisTadel)