Eye movements, eye blinks, cardiac signals, muscle noise,
and line noise present serious problems for electroencephalographic
(EEG) interpretation and analysis when rejecting contaminated
EEG segments results in an unacceptable data loss. Many
methods have been proposed to remove artifacts from EEG
recordings, especially those arising from eye movements
and blinks. Often regression in the time or frequency domain
is performed on parallel EEG and electrooculographic (EOG)
recordings to derive parameters characterizing the appearance
and spread of EOG artifacts in the EEG channels. Because
EEG and ocular activity mix bidirectionally, regressing
out eye artifacts inevitably involves subtracting relevant
EEG signals from each record as well. Regression methods
become even more problematic when a good regressing channel
is not available for each artifact source, as in the case
of muscle artifacts. Use of principal component analysis
(PCA) has been proposed to remove eye artifacts from multichannel
EEG. However, PCA cannot completely separate eye artifacts
from brain signals, especially when they have comparable
amplitudes. Here, we propose a new and generally applicable
method for removing a wide variety of artifacts from EEG
records based on blind source separation by independent
component analysis (ICA). Our results on EEG data collected
from normal and autistic subjects show that ICA can effectively
detect, separate, and remove contamination from a wide
variety of artifactual sources in EEG records with results
comparing favorably with those obtained using regression
and PCA methods. ICA can also be used to analyze blink-related
brain activity.