Abstract
The causes of ocular artefacts (OAs) in the human electroencephalogram (EEG) are explained and methods for their removal and their effectiveness are discussed. Recommendations for the best procedures to adopt are given together with suggestions for future research. Analogue subtraction techniques are found to be inferior to time domain techniques based on parameter estimation using the method of least squares applied to a linear function of the electro-occulograms (EOGs). Ways of assessing the effectiveness of different models for time domain removal of OAs are discussed. It is concluded that autoregressive modelling of the error terms, or else differenced data, must be used to reduce the effects of correlation in the background EEG. The most generally suitable model for the removal of random eye and blink artefacts should contain terms proportional to the right vertical EOG and the two horizontal EOGs. The EOGs should be linearly filtered to remove noise frequency components in excess of 8 Hz. Adaptive methods are preferred as on line OA removal would be desirable but for the fact that this may result in distortion of stimulus-related responses present. A number of difficulties remain and there are some suggestions for future research.
Similar content being viewed by others
References
Barlow, J. S. (1979) Computerized clinical electroencephalography in perspective.IEEE. Trans.,BME-26, 377–391.
Barlow, J. S. andRémond, A. (1981) Eye movement artifact nulling in EEGs by multichannel on-line EOG subtraction.Electroenceph. & Clin. Neurophysiol.,52, 418–423.
Barry, W. andJones, G. M. (1965) Influence of eyelid movement upon electro-occulographic recording of vertical eye movements.Aerospace Med.,36, 855–858.
Berg, P. (1986) The residual after correcting event-related potentials for blink artefacts.Psychophysiology,23, 354–364.
Bierman, G. J. (1976) Measurement up-dating using the U-D factorization.Automatica,12, 375–382.
Borda, P. R. andHablitz, J. J. (1973) Use of a simple visual display to reduce eye movement artifacts in CNV recordings.Electroenceph. & Clin. Neurophysiol.,34, 433–436.
Connolly, J. F. andKleiman, K. M. (1978) A single channel method for recording vertical and lateral eye movements.,45, 128–129.
Corby, J. C. andKopell, B. S. (1972) Differential contributions of blinks and vertical eye movements as artifacts in EEG recording.Psychophysiology,9, 640–644.
Elbert, T., Lutzenberger, W., Rockstroh, B. andBirmbaumer, N. (1985) Removal of ocular artefacts from the EEG—a biophysical approach to the EOG.Electroenceph. & Clin. Neurophysical.,60, 455–463.
Ford, A. (1959) Significance of terminal transients in electro-oculographic recordings.Arch. Opthalmol.,61, 899–906.
Fortgens, C. andDe Bruin, M. P. (1983) Removal of eye movement and ECG artifacts from the non-cephalic reference EEG.Electroenceph. Clin. Neurophysiol.,56, 90–96.
Gasser, T., Sroka, L. andMöcks, J. (1985) The transfer EOG activity into the EEG for eyes open and closed.,61, 181–193.
Gasser, T., Sroka, L. andMöcks, J. (1986) The correction of EOG artifacts by frequency dependent and frequency independent methods.Psychophysiology,23, 704–712.
Geddes, L. A., McCrady, J. D. andHoff, H. E. (1965) The impedance nystagmogram—a record of the level of anaesthesia in the horse.South Western Veterinarian,19, 23–25.
Gevins, A. S., Yeager, C. L., Zeitlin, G. M., Ancoli, S. andDedon, M. F. (1977) On-line computer rejection of EEG artefacts.Electroenceph. & Clin. Neurophysiol.,42, 267–274.
Girton, D. G. andKamiya, J. (1973) A simple on-line technique for removing eye movement artifacts from the EEG.,34, 212–216.
Gotman, J., Skuce, D. R., Thompson, C. J. Gloor, P., Ives, J. R. andRay, W. F. (1973) Clinical applications of spectral analysis and extraction of features from electroencephalograms with slow waves in adult patients.,35, 225–235.
Gratton, G., Coles, M. G. H. andDonchin, E. (1983) A new method for off-line removal of ocular artifacts.,55, 468–484.
Hamer, C. F., Ifeachor, E. C. andJervis, B. W. (1985) Digital filtering of physiological signals with minimal distortion.Med. & Biol. Eng. & Comput.,23, 274–278.
Harlan, W. L., White, P. T. andBickford, R. G. (1958) Electric activity produced by eye flutter simulating frontal electroencephalographic rhythms.Electroenceph. & Clin. Neurophysiol.,10, 164–169.
Harris, C. J. (1983) Brain waves appear on TV in real-time.Electronics, Feb., 47–48.
Henderson, C. J., Butler, S. R. andGlass, A. (1975) The localisation of equivalent dipoles of EEG sources by the application of electrical field theory.Electroenceph. & Clin. Neurophysiol.,39, 117–130.
Hillyard, S. A. andGalambos, R. (1970) Eye movement artifact in the CNV.,8, 173–182. See also Section 4.3.
Hillyard, S. A. (1974) Methodological issues in CNV research. InBioelectric recording techniques part B. electroencephalography and human brain potentials.Thompson, R. F. andPatterson, M. M. (Eds.), Academic Press, 259–280.
Ifeachor, E. C. (1984) Investigation of ocular artefacts in the human EEG and their removal by a microprocessor-based instrument. Ph.D. Thesis, Plymouth Polytechnic, Dec. 1984.
Ifeachor, E. C., Jervis, B. W., Allen, E. M., Morris, E. L. andHudson, N. R. (1985) A microcomputer-based instrument for on-line ocular artefact removal. 11th Int. Congr. Electroenceph. and Clin. Neurophysiol., London, 25–30th Aug.,Electroenceph. & Clin. Neurophysiol.,61, S247.
Ifeachor, E. C., Jervis, B. W., Morris, E. L., Allen, E. M. andHudson, N. R. (1986a) New on-line method for removing ocular artefacts from EEG signals.Med. & Biol. Eng. & Comput.,24, 356–364.
Ifeachor, E. C., Jervis, B. W., Morris, E. L., Allen, E. M. andHudson, N. R. (1986b) A new microcomputer-based on-line ocular artefact removal (OAR) system.Proc. IEE,133A, 291–300.
Jervis, B. W., Nichols, M. J., Allen, E. M., Hudson, N. R. andJohnson, T. E. (1980) The quantitative assessment of electroencephalograms corrected for eye movement artefact. 1st Europ. Signal Proc. Conf., Lausanne, Switzerland, September.
Jervis, B. W., Allen, E. M., Johnson, T. E., Nichols, M. J. andHudson, N. R. (1984) The application of pattern recognition techniques to the contingent negative variation for the differentiation of subject categories. -31, 342–349.
Jervis, B. W., Nichols, M. J., Allen, E. M., Hudson, N. R. andJohnson, T. E. (1985a) The assessment of two methods for removing eye movement artefact from the EEG.Electroenceph. & Clin. Neurophysiol.,61, 444–452.
Jervis, B. W., Ifeachor, E. C., Allen, E. M., Morris, E. L. andHudson, N. R. (1985b) Removal of ocular artefacts from the human EEG. 7th Ann. Conf. Frontiers of Eng. and Comput. in Health Care, IEEE Engineering in Medicine & Biology Society, Chicago, USA 27th–30th September,1, 101–107.
John, E. R., Karmel, B. Z., Corning, W. C., Easton, P., Brown, D., Ahu, H., John, M., Harmony, T. Prichep, L., Toro, A., Gerson, I., Bartlett, F., Thatcher, R., Kaye, H. Valdes, P. andSchwartz, E. (1977) Neurometrics.Science, 24th June,196, 1393–1410.
Low, M. D., Borda, R. P., Frost, J. D. andKellaway, P. (1966). Surface negative slow potential shift associated with conditioning in man.Neurology,16, 771–782.
Matsuo, F., Peters, J. F. andReilly, E. L. (1975) Electrical phenomena associated with movements of the eyelid.Electroenceph. & Clin. Neurophysiol.,38, 507–511.
McCallum, W. C. andWalter, W. H. (1968) The effects of attention and distraction on the contingent negative variation in normal and neurotic subjects.,25, 319–328.
Muras, J. S. andBinnie, C. D. (1970) The recognition of frontal slow activity in the presence of eye movements.Proc. Electrophysiological Technol. Assoc.,17, (2), 131–143.
Overton, D. A. andShagass, C. (1969) Distribution of eye movement and eye blink potentials over the scalp.Electroenceph. & Clin. Neurophysiol.,27, 546.
Papakostopoulos, D., Winter, A. andNewton, P. (1973) New techniques for the control of eye potential artefacts in multi-channel CNV recordings.,34, 651–653.
Quilter, P. M., Macgillivray, B. B. andWadbrook, D. G. (1977). The removal of eye movement artefact from EEG signals using correlation techniques. InRandom signal analysis. IEE Conf. Publ. 159, 93–100.
Reiman, V., Korth, M. andKeidel, W. D. (1974) Korrelations Analyse von EEG und Augenbewengungen.Vision Res.,14, 959–963.
Rowland, V. (1968) Cortical steady potential (direct current potential) in reinforcement and learning. InProgress in physiological psychology, vol. 2.Stellar, E. andSprague, J. M. (Eds). Academic Press, New York, 1–77.
Shackell, B. (1967) Eye movement recording by electro-oculography. InA manual of psychophysiological methods.Venables, P. H. andMartin, I. (Eds.), North Holland, 301–334.
Straumanis, J. J., Shagass, C. andOverton, D. A. (1969) Problems associated with applications of the contingent negative variation to psychiatric research.J. Nervous & Mental Dis.,148, 170–179.
Sullivan, G. H. andWelfmen, G. (1963) The impedance oculograph—A new technique.J. Appl. Physiol.,18, 215–216.
Verleger, R., Gasser, T. andMocks, J. (1982) Correction of EOG artifacts in event-related potentials of the EEG: aspects of reliability and validity.Psychophysiology,19, 472–480.
Wasman, M., Morehead, S. D., Lee, H. andRowland, V. (1970) Interaction of electro-ocular potentials with the contingent negative variation.,7, 103–111.
Weerts, T. C. andLang, P. J. (1973) The effects of eye fixation and stimulus and response location on the contingent negative variation (CNV).Biol. Psych.,1, 1–19.
Whitton, L., Leu, F. andMoldofsky, H. (1978) A spectral method for removing eye movement artifacts from the EEG.Electroenceph. & Clin. Neurophysiol.,44, 735–741.
Woestenburg, J. C., Verbaten, M. N. andSlagen, J. L. (1983) Removal of the eye movement artifact from the EEG by regression analysis in the frequency domain.Biol. Psychol.,16, 127–147.
Young, L. R. andSheena, D. (1975) Survey of eye movement recording methods.Behaviour Res. Meth. & Instrum.,7, 397–429.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Jervis, B.W., Ifeachor, E.C. & Allen, E.M. The removal of ocular artefacts from the electroencephalogram: a review. Med. Biol. Eng. Comput. 26, 2–12 (1988). https://doi.org/10.1007/BF02441820
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF02441820