Filtering scope

Module information
Modules	BESA Research
Version	6.1 or higher

In EEG/MEG data analysis frequency filtration is one of the most basic and at the same time important operations. In BESA Research filtration is implemented as a linear operation so it is interchangeable in the processing pipeline - it can be changed at every processing step in almost all situations. There are however some moments that filtration cannot be applied in a linear manner - i.e. averaging. In general, we recommend not apply filtration during such types of operations as it can be replied afterward. You will be prompted by the application if you encounter such a moment in data analysis:

Also at some stages of the data processing, the filtration is of major importance, therefore we made it more accessible and you can easily redefine it. Please have a look at the table below:

Filter type	Review window	Search Average View	Averaged buffer	FFT	lienear corelation / regression	Combine Conditions	ERP	Coherence	Time Frequency plot (single click)	TopViewer	Source Analysis
Low/High pass	Main	Main / can be redefine to default values(2-35Hz)	as used during buffer creation	Main	Main	None	ERP	ERP	Main	Main	SA
Notch	Main	Main / can be redefine to default values(2-35Hz)	as used during buffer creation	Main	Main	None	Main	Main	Main	Main	Main
Bandpass	Main	Main / can be redefine to default values(2-35Hz)	as used during buffer creation	Main	Main	None	ERP	ERP	Main	Main	Main
Polygraphic	Main*	Main* / can be redefine to default values(2-35Hz)	as used during buffer creation	Main*	Main*	None	Main*	Main*	Main*	Main*	n.a.
artifact correction	Main	Main / can be redefine to default values(2-35Hz)	as used during buffer creation	Main	Main	Main	ERP	ERP	Main	Main	Main/SA

Main settings

The main setting for artifact correction can be set using EdF or menu entry Filters/Edit Filter Settings...

Specific ERP settings

The ERP filter settings can be set during paradigm definition. Note that there are two different settings - for artifact scan and for averaging

Specific Source Analysis settings

For source analysis (SA), if you press 'ESI/MSI button on the toolbar ribbon Main filter settings will be used.) Filters for SA can be set during sending a block of data to Source Analysis (right-click on the highlighted block and select Source Analysis).

Notch filter

Note that because of its generic nature - power line artifact removal - notch filter is treated differently. The notch filter value populates from Main setting to all subsequent applications.

Bandpass filter

Bandpass filter is complementary to high/low pass filter combination. For convenience, it is treated differently and also populates to all subsequent applications from Main setting.

Polygraphic filter

Polygraphic channels are filtered using Main settings. Note that there are additional settings that can be applied to the polygraphic filter accessible via Filters/Polygraphic/Additional Chans...