62: EEG automatic sensor localization
Automatic determine the locations of EEG scalp sensors using 10-20 system using scalp mesh extracted from MRI. Refer to wiki for the definition of electrodes in the 10-20 system.
Four landmarks are needed: LPA, RPA, Nasion, Inion. These four landmarks can be manually localized with the procedure below.
NOTE: etc_render_fsbrain can open an electrode/sensor localization GUI by pressing the b key.
Given the four landmarks, sensors in Modified Combinatorial Nomenclature (MCN) high-definition EEG can be marked automatically. [This script file] defines 61 sensors over the scalp.
In this script, a variable sensor with field named coords must be provided in the file (sensor_landmarks.mat in this example). The (x,y,z) coordinates of LPA, Nasion, RPA, and Inion are at the following:
sensor.coords(1,:): coordinates for LPA sensor.coords(2,:): coordinates for Nasion sensor.coords(3,:): coordinates for RPA sensor.coords(4,:): coordinates for Inion
Successful localization will show the electrodes and arcs over the scalp in electrode localization. The coordinates and names of electrodes and four landmarks will be stored in variables p and labels, respectively. Both will be saved in a matlab mat file (eeg_auto1020_077922.mat in this example).
The arcs are auxiliary guides for placing electrodes.
All 63 electrodes and 4 landmarks.
The GUI for all 63 electrodes and 4 landmarks.
