Brain Topography

, Volume 6, Issue 1, pp 65–78 | Cite as

Ocular artifacts in recording EEGs and event-related potentials II: Source dipoles and source components

  • Otavio G. Lins
  • Terence W. Picton
  • Patrick Berg
  • Michael Scherg


The source dipoles for blinks point radially whereas the source dipoles for saccades point tangentially, in the direction of the eye movement. This indicates that blink potentials are not generated by eye movements but by the eyelid sliding down over the positively charged cornea. Dipole source dipole analysis shows that the “rider artifact” at the onset of upward and lateral saccades is caused by the eyelid as it lags a little behind the eyes at the beginning of the movement. Dipole source analysis allows both the EEG and the EOG to be modeled simultaneously and EOG generators to be distinguished from nearby EEG generators. Ocular source components can be calculated from a principal component analysis of EEG and EOG recordings during blinks and saccades. The effectiveness of propagation factors, source dipoles and source components in removing ocular artifacts from EEG samples was assessed. The most effective correction procedure uses source components.

Key words

Electro-oculogram EOG EEG artifacts Source analysis Principal component analysis 


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  1. Barlow, J.S. and Rémond, A. Eye movement artifact nulling in EEGs by multichannel on-line EOG subtraction. Electroencephalogr. Clin. Neurophysiol., 1981: 418–423.Google Scholar
  2. Barry, W. and Jones G.M. Influence of eye lid movement upon electro-oculographic recording of vertical eye movements. Aerosp. Med., 1965, 36: 855–858.PubMedGoogle Scholar
  3. Becker, W. and Fuchs, A.F. Lid-eye coordination during vertical gaze changes in man and monkey. J. Neurophysiol., 1988, 60: 1227–1252.PubMedGoogle Scholar
  4. Berg, P. and Scherg, M. Dipole models of eye movements and blinks Electroencephalogr. Clin. Neurophysiol., 1991a, 79: 36–44.PubMedGoogle Scholar
  5. Berg, P. and Scherg, M. Dipole modeling of eye activity and its application to the removal of eye artifacts from the EEG and MEG. Clin. Phys. Physiol. Meas., 1991b; 12 (Supplement A): 49–54.PubMedGoogle Scholar
  6. Brunia, C.H.M., Mocks, J., van den Berg-Lenssen, M.M.C. et al. Correcting ocular artifacts in the EEG: A comparison of several methods. J. Psychophysiol., 1989, 3: 1–50.Google Scholar
  7. Collewijn, H., Van Der Steen, J. and Steinman, R.M. Human eye movements associated with blinks and prolonged eyelid closure. J. Neurophysiol., 1985, 54: 11–27.PubMedGoogle Scholar
  8. Elbert, T., Lutzenberger, W., Rockstroh, B. and Birbaumer, N. Removal of the ocular artifacts from the EEG—A biophysical approach to the EOG. Electroencephalogr. Clin. Neurophysiol., 1985, 60: 455–463.PubMedGoogle Scholar
  9. Evinger, M.D., Shaw, C.K., Manning, K.A. and Baker, R. Blinking and associated eye movement in humans, guinea pigs and rabbits. J. Neurophysiol., 1984, 52: 323–38.PubMedGoogle Scholar
  10. Gasser, T., Sroka, L. and Mocks, J. The correction of EOG artifacts by frequency dependent and frequency independent methods. Psychophysiology, 1986, 23: 704–712.PubMedGoogle Scholar
  11. Gratton, G., Coles, M.G.H. and Donchin, E. A new method for off-line removal of ocular artifact. Electroencephalogr. Clin. Neurophysiol., 1983, 55: 468–484.PubMedGoogle Scholar
  12. Häkkinen, V., Hirvonen, K., Hasan, J., Kataja, M., Värri, A., Loula, P. and Eskola, H. Effects of small differences in electrode positions on EOG signals. Application to vigilance studies. Electroencephalogr. Clin. Neurophysiol., 1993, 86: 294–300.PubMedGoogle Scholar
  13. Hector, M.L. EEG recording. Butterworths, London, 1976.Google Scholar
  14. Hillyard, S.A. and Galambos, R. Eye movement artifact in the CNV. Electroencephalogr. Clin. Neurophysiol., 1970, 28: 173–182.PubMedGoogle Scholar
  15. Ifeachor, E.C., Jervis, B.W., Allen, E.M., Moris, E.L., Wright, D.E. and Hudson, N.R. Investigation and comparison of some models for removing ocular artifacts from EEG signals. Med. Biol. Eng. Comput., 1988, 26: 584–590; 591–598.PubMedGoogle Scholar
  16. Jervis, B.W., Nichols, M.J., Allen, E.M., Hudson, N.R. and Johnson, T.E. The assessment of two methods for removing eye movement artifact from the EEG. Electroncephalogr. Clin. Neurophysiol., 1985, 61: 444–452.Google Scholar
  17. Jervis, B.W., Ifeachor, E.C. and Allen, E.M. The removal of ocular artifacts from the electroencephalogram: a review. Med. Biol. Eng. Comput., 1988, 26: 2–12.PubMedGoogle Scholar
  18. McCallum, W.C. and Walter, W.G. The effects of attention and distraction on the contingent negative variation in normal and neurotic subjects. Electroencephalogr. Clin. Neurophysiol., 1968, 25: 319–329.PubMedGoogle Scholar
  19. Möcks, J. and Verlenger R. Multivariate methods in biosignal analysis: application of principal component analysis to event-related potentials. In: R. Weitkunat (Ed.), Digital Biosignal Processing. Techniques in the Behavioral and Neural Sciences. Vol 5. Amsterdam, Elsevier, 1991: 399–458.Google Scholar
  20. Nunez, P.L. and Katznelson, R.D. Electric fields of the brain: the neurophysics of EEG Oxford, New York, 1980.Google Scholar
  21. Scherg, M. Fundamentals of dipole source analysis. In: M. Hoke, F. Grandori and G.L. Romani (Eds.), Advances in Audiology, Vol 6. Auditory Evoked Magnetic Fields and Potentials. Basel, Karger, 1990: 40–69.Google Scholar
  22. Scherg, M. and Von Cramon, D. Dipole source potentials of the auditory cortex in normal subjects and patients with temporal lobe lesions. In: F. Grandori, M. Hoke and G.L. Romani (Eds.), Advances in Audiology, Vol 6. Auditory Evoked Magnetic Fields and Potentials. Basel, Karger, 1990: 165–193.Google Scholar
  23. Scherg, M. and Picton, T.W. Separation and identification of event-related potential components by brain electric source analysis. In: C.H.M. Brunia, G. Mulder and M.N. Verbaten (Eds.), Event-Related Potentials of the Brain. Electroencephalogr. Clin. Neurophysiol., Suppl. 42, Elsevier, Amsterdam, 1991: 24–37.Google Scholar
  24. Scherg, M. Functional imaging and localization of electromagnetic brain activity. Brain Topography, 1992, 5: 103–111.PubMedGoogle Scholar
  25. Semlitsch, H.V., Anderer, P., Schuster, P. and Presslich, O. A solution for reliable and valid reduction of ocular artifacts, applied to the P300 ERP. Psychophysiology, 1986, 23: 965–703.Google Scholar
  26. Whitton, J.L., Lue, F. and Moldofsky, H. A spectral method for removing eye movement artifacts from the EEG. Electroencephalogr. Clin. Neurophysiol., 1978, 44: 735–741.PubMedGoogle Scholar

Copyright information

© Human Sciences Press, Inc 1993

Authors and Affiliations

  • Otavio G. Lins
    • 1
  • Terence W. Picton
    • 1
  • Patrick Berg
    • 2
  • Michael Scherg
    • 3
  1. 1.Human Neurosciences Research UnitUniversity of OttawaCanada
  2. 2.Department of PsychologyUniversity of KonstanzGermany
  3. 3.Department of NeuroscienceAlbert Einstein College of MedicineBronxUSA

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