Scanning and displaying dipoles

Authors: Elizabeth Bock, Francois Tadel, John C Mosher

In Brainstorm, the brain activity is typically estimated with distributed source models including thousands of dipoles, and represented as cortical maps or functional overlays on the MRI. Another common way of representing the source activity is to consider there is only one single active dipole that can explain most of the MEG/EEG recordings.

We offer two options to estimate the position and orientation of the most significant dipole at each time point: a dipole scanning method, which selects the most significant dipole in a grid of dipoles that are already estimated, and a non-linear dipole fitting method, which searches iteratively for the dipole that explains the best the recordings. The former is described on this page, the latter in another tutorial: FieldTrip dipole fitting.

Dipole modeling

The example below uses the protocol TutorialIntroduction created in the introduction tutorials.

Dipole scanning

The process Sources > Dipole scanning searches the grid of dipoles computed previously for the most significant location. The information from the three orientations (x,y,z) are combined to get the optimal orientation at the best location.

Displaying dipoles

We have 25 dipoles saved in this file, one per time sample between 60ms and 100ms. You can use the Dipoles tab to display only the most significant dipoles, and change the way they are colored.

Dipole information

Description of the measures displayed in the "Dipole info" window:

Neuromag Xfit and CTF DipoleFit

Brainstorm can import dipole files that have been generated using external software:

Importing a dipole file


Additional documentation

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Tutorials/TutDipScan (last edited 2016-10-17 23:21:43 by FrancoisTadel)