Sam hfo

From MEG Core
Jump to navigation Jump to search

Return to Source Localization - SAM


The sam_hfo program is an experimental program which may aid in the localization of epileptiform activity. This program first bandpass filters the data to visualize high frequency activity only (typically above 150Hz). For each voxel in the image, a time-series is computed and a Hilbert envelope is applied to the source. Excess kurtosis of the Hilbert envelope is used to localize potential events, such as short bursts of high frequency oscillations (HFOs). Before running sam_hfom epoched data must be saved in a continuous format.


 sam_hfo -r <dataset_name> -m <parameter_file_name> [options]

The -r flag designates the dataset name (with or without the .ds suffix), and -m designates the parameter file name.

Other options:

 -v  Verbose mode, without this flag sam_wts works silently except for error messages

Required Parameters:

 CovBand: Bandwidth used for covariance matrix calculation
 ImageBand: Bandwidth used for covariance matrix calculation
 SmoothBand: designates the lowpass filter for smoothing the Hilbert envelope
 CovType: Must be GLOBAL
 ImageMetric: Must be KURTOSIS

Optional Parameters:

 FilterType: choose the applied filter, IIR vs. FFT 
 ImageDirectory: Directory where the output images are written, default is the SAM directory
 PrefixLength: Number of characters in the MEG dataset name used for naming MRI files

Output Files

sam_hfo Creates a single 3D NIFTI format image of kurtosis (g2) of the Hilbert envelope of high frequency activity. The output file will be named using the PrefixLength parameter, and will be appended with "HFO."