Spatial Directionality Found in Frontal-Parietal Attentional Networks
Table 2
Signal processing procedure.
Steps
Description
(1) Data Preprocessing
Low-pass filter – Focus on frequencies below 40Hz.
(2) Signal Decomposition
Fast Fourier Transform – Extract real and imaginary parts of the signal.
(3) Electrode Pair Selection
Magnitude squared coherence is initially performed on electrode pairs considered to have significant coherence (> 0.6) for selection
(4) Unwrap Phase Function
The “unwrap” phase function is applied in order to return the phase angles in radians
(5) Mean and standard deviation calculation
For all the channels, the mean and the standard deviation were calculated.
(6) Directionality property analysis
Directionality is determined by the slope of mean of the unwrapped phases, which is either positive or negative, thereby constituting phase lead or phase lag. Phase directionality is designated as phase leads of the unwrapped phases between channels. Slope values are plotted to determine phase directionality in reference to each channel.