title: Removal of eye activity artifacts from visual event-related potentials in normal and clinical subjects.
abstract: OBJECTIVE
  Electrical potentials produced by blinks and eye movements present serious problems for electroencephalographic (EEG) and event-related potential (ERP) data interpretation and analysis, particularly for analysis of data from some clinical populations. Often, all epochs contaminated by large eye artifacts are rejected as unusable, though this may prove unacceptable when blinks and eye movements occur frequently.
  
  
  METHODS
  Frontal channels are often used as reference signals to regress out eye artifacts, but inevitably portions of relevant EEG signals also appearing in EOG channels are thereby eliminated or mixed into other scalp channels. A generally applicable adaptive method for removing artifacts from EEG records based on blind source separation by independent component analysis (ICA) (Neural Computation 7 (1995) 1129; Neural Computation 10(8) (1998) 2103; Neural Computation 11(2) (1999) 606) overcomes these limitations.
  
  
  RESULTS
  Results on EEG data collected from 28 normal controls and 22 clinical subjects performing a visual selective attention task show that ICA can be used to effectively detect, separate and remove ocular artifacts from even strongly contaminated EEG recordings. The results compare favorably to those obtained using rejection or regression methods.
  
  
  CONCLUSIONS
  The ICA method can preserve ERP contributions from all of the recorded trials and all the recorded data channels, even when none of the single trials are artifact-free.
authors.affiliation: University of California, San Diego, La Jolla, CA 92093, USA. jung@salk.edu
authors.forename: T P
authors.initials: TP
authors.lastname: Jung
authors.forename: S
authors.initials: S
authors.lastname: Makeig
authors.forename: M
authors.initials: M
authors.lastname: Westerfield
authors.forename: J
authors.initials: J
authors.lastname: Townsend
authors.forename: E
authors.initials: E
authors.lastname: Courchesne
authors.forename: T J
authors.initials: TJ
authors.lastname: Sejnowski
mesh_terms: D000328:Adult; D016477:Artifacts; D001321:Autistic Disorder / Q000503:physiopathology; D001767:Blinking / Q000502:physiology; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009799:Ocular Physiological Phenomena; D020521:Stroke / Q000503:physiopathology