Common ICA components (Find more example of artifactual components in this document)
Alpha oscillations: The ICA components have a clear 8-13 Hz frequency, which is also seen in the power spectrum.
The component statistics show that the activity has an almost normal distribution, as we would expect for a signal from the brain.
The topography also shows a dominance in the parietal region as expected for alpha oscillations.
Eye artifacts are characterized by slow, but strong changes in component activity.
The power spectrum has no alpha peak.
The component statistics show that the activity does not have normal distribution.
The topography has a dominance in the eye region.
The component activity of a heart beat (signal nr 4) has ~ 1 Hz frequency.
The component activity has a broad power spectrum.
The component activity does not have a normal distribution.
The topography is not localized but covers the whole scalp.
ICA analysis can also be computed in NBT GUI
go to Pre-processing|ICA|Run ICA on good channels only
go to Pre-processing|ICA|Filter ICA components
use the visualization tools for detecting the first round of bad components
go to Visualization|ICA|Plot component activations
go to Visualization|ICA|Plot spectra and maps
go to Visualization|ICA|Components statistics
go to Visualization|ICA|Reject component by map
once you selected the first bad components go to Pre-processing|ICA|Mark ICA components as bad
repeat points 1,2,3
go to Pre-processing|ICA|Reject filtered ICA components
Finally to re-reference your data click Pre-processing|Re-reference to average reference (exclude bad channels), and to save your data click File|Save NBT Signal. When asked for NBT Signal name write ICASignal and select the folder where you want to store your signal (we recommend to use the folder where the original data file is).