BrainVoyager v23.0

EEG/MEG Data Filtering

This section provides a short description of the BrainVoyager QX EEG/MEG data filtering module that allows filtering EEG and MEG data sets and eventually update channel and configuration and protocol data before entering the EMEG Suite. The EEG/MEG Data Filter functionality can be invoked from the EEG-MEG menu (Filter EEG/MEG data ...)

The digital filters in BrainVoyager QX can be used to suppress unwanted low and high frequency noise or to enhance a periodic pattern around the frequency of interest. BrainVoyager QX supports low-pass, high-pass, band-pass and notch filter types. Filter types and orders can conveniently be changed via the interface. In addition, decimation and scaling factor can be specified to change the sampling frequency and the magnitude order of the signals.

The Low cut-off and the High cut-off check boxes allow to specify a Butterworth filter, whose order can be changed using the corresponding spin box. Importantly, enabling the low but not the high cut-off defines a high-pass filter, whereas enabling the high but not the low cut-off defines a low-pass filter. Enabling both cut-offs defines a band pass filter. A notch filter is also available for suppression of noise in narrow frequency bands, with a customizable central frequency.

Besides (or in alternative to) filtering, it is possible to change the sampling rate and amplitude scaling (e. g. for adapting physicial units to uV or fT/m) of the continous channel time-course using the corresponding check boxes in the dialog for decimation and scaling. The scaling factor should be interpreted as a power of 10. For EEG data, it is possible to change the reference potential to the "average channel" reference (average reference).