WB_EEG_REST is a tool of Reference Electrode Standardization Technique (REST) in WeBrain. REST is a re-reference technique, a software method for translating multichannel spontaneous EEG or event-related potentials with reference at any a physical point on brain/body surface or the post-processed data referenced at average or linked ears etc. to a new dataset with reference at Infinity where the potential is zero/constant (Yao, 2001; Yao et al., 2005). Currently, REST is increasingly acknowledged by EEG/ERPs community around the world (to our knowledge, at least 12 countries/areas), and more than 50 studies have actually adopted REST to get zero reference as the foundation of their novel findings. Meanwhile, the REST has been regarded as the Rosetta Stone for scalp EEG (Kayser and Tenke, 2010) and listed in the new guidelines of International Federation of Clinical Neurophysiology (IFCN) for EEG analysis. More details about REST toolbox can also be seen in the paper (Dong et al., 2017).
Use REST please cite:
Yao, D., 2001. A method to standardize a reference of scalp EEG recordings to a point at infinity. Physiol Meas. 22, 693-711.
Dong, L., et al., 2017. MATLAB Toolboxes for Reference Electrode Standardization Technique (REST) of Scalp EEG. Frontiers in Neuroscience. 11.
lfFile: Leadfield file.The leadfield can be a matrix (*.dat, output of leadfield.exe, sources X channels) which is calculated by using the forward theory, based on the electrode montage, head model and equivalent source model. It can also be the output of ft_prepare_leadfield.m (e.g. lf.leadfield) based on real head modal using FieldTrip.
rechanns: string with indices of the re-referenced channels (channels re-referencing to REST, e.g. ‘[1:4,7:30]’), or ‘all’.
For each subject, a zip file which contain the re-referenced EEG data will be generated (saved as EEG .set file which contains the EEG potentials with zero reference, channels × time points).
The leadfield matrix is required to be calculated for a new electrode system. It can be the output of ft_prepare_leadfield.m (e.g. lf.leadfield) based on real head modal using FieldTrip. Users can also download the ‘Leadfield.exe’ to calculate a leadfield matrix of a concentric-three-spheres head model. It calculates the leadfield matrix from the 3000 cortical dipoles (spherical equivalent dipoles) and the newly given electrode array for the canonical concentric-three-spheres head model. The array of real electrode coordinates (coordinates of fiducial points are not required) is suggested to be saved in a ‘*.txt’ ASCII file with their Cartesian x (the left ear is defined as -x axis), y (the nasion is the +y axis), z coordinates in three columns, while the coordinates will be auto-normalized and -matched to the upper spherical cap of head model inside the program. In addition, noting that the executable file ‘Leadfield.exe’ is compiled using C language on Windows system to calculate the leadfield matrix; if you want to run it on Linux system (Ubuntu), a simple solution is to install the ‘Wine’ software first (i.e. enter the command ‘sudo apt-get install wine’ in a terminal). The leadfield calculation consists of the following 2 steps.
1. File → Load Electrode File: ‘*.txt’ ASCII file; x, y, z positions in three columns only;
2. File → Calculate Lead Field. It may take a few minutes that depends on the size of the matrix and the computer. When the calculation is completed, the leadfield matrix is saved as ‘Lead_Field.dat’ (sources × channels) in the directory of electrode file.
The reference of input EEG data should be a scalp point (e.g. the tip of the nose, vertex, linked mastoids or linked ears) or average reference.
http://www.fieldtriptoolbox.org/referen ... _leadfield
http://www.fieldtriptoolbox.org/develop ... xample_fem
http://www.fieldtriptoolbox.org/tutoria ... =headmodel
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