Computing and Visualizing Dipoles

Computing sources using the GLS

This process allows for a systematic scanning of sources using performance measures to display single dipoles. For this tutorial we will use the Generalized Least Squares (GLS) source modeling available in Brainstorm.

1. Select the protocol TutorialCTF. Right-click on Subject01 / Left / ERF > Compute sources.

2. In this window, you should select Expert Mode. You will see the following menu. Select [Test] Mosher GLS. Click OK. Use the default settings in the next menu and click OK.
   
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3. Two results were added under the ERF: GLS and GLS-P.
   
   

   • GLS:

   • GLS-P:

Dipole Scanning

1. Drag and drop the GLS-P link into the Process 1 box. Click Run > Sources > Dipole scanning.
   
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2. Use the defaults options:

   • Time Window: This is the window over which the scanning will occur. The default option is to use the entire epoch.

   • Time between dipoles: This allows you to change the resolution of the scanning. To use all time points, enter a 0 (default).
     
     

3. The resulting dipole file is added under the Left condition.
   
   

Visualizing Dipoles

1. Right-click ERF|GLSP-dipole-scan > Display on cortex. The Dipoles panel is now open and dipoles are displayed on the cortex. You can now explore the results using the options in the Dipoles panel:
   
   

   • Data options: filter the available dipoles according the specific measurement. For the GLSP, these are defined as:

     • Z-score:

     • Goodness:

     • Chi-square:

     • Reduced Chi-square:

     • Confvolume:

   • Display options: these options allow for adjusting how the selected dipoles (according to the Data options) are displayed

     • Show max goodness: will show the dipole with the maximum goodness (within the constraints of the Data options) at the time point selected. If Show all time is selected, then this represents the maximum goodness over all time points.

     • Show all time: plots all selected dipoles at all time points. Un-selecting this options will show only the current time point.

     • 3D - Color dipoles according to Time, Goodness of Fit, Z-score, Group: adjusts the colormap to reflect the measure.

2. In the Dipoles panel, select Show max goodness of fit, Show all time, and color the dipoles according to Goodness of Fit. You should see the following display. Explore the panel options to familiarize yourself with the capabilities.