Abstract
A method of estimating equivalent moving and fixed dipoles from the scalp-recorded EEG alpha waves, with the realistic geometry of the head taken into account, is presented. Twenty-one silver electrodes were used to collect spontaneous EEG alpha waves on the scale. Four models, the single-moving dipole model, the single-fixed dipole model, the two-moving dipole model and the two-fixed dipole model were applied to approximate the EEG alpha field on the scalp. The algorithm, based on a least-squares fit for estimating the moving and the fixed dipoles by using a realistically shaped head model, is described. The numerical accuracy of the algorithm is also evaluated by a computer simulation. It is found that the spontaneous EEG alpha activity observed on the scalp can be represented by two equivalent moving dipoles, simultaneously located separately in the occipital regions of the right and the left hemisphere, at a depth of 4–6 cm beneath the scalp, with a goodness-of-fit of up to 97 per cent for all subjects examined. The excellent fit of the two-moving dipole model to the EEG human alpha activity is also compared with the single-dipole fit.
Similar content being viewed by others
References
Aoki, M., Okamoto, Y., Musha, T. andHarumi K. (1987) Three-dimensional simulation of the ventricular depolarization and repolarization processes and body surface potentials: normal heart and bundle branch block.IEEE Trans.,BME-34, 454–462.
Brebbia, C. A. andWalker, S. (1980)Boundary element techniques in engineering, Butterworth & Co. Ltd, London.
Chapman, R. M., Ilmoniemi, R. J., Barbanera, S. andRomani, G. L. (1984) Selective localization of alpha brain activity with neuromagnetic measurements.Electroenceph. Clin. Neurophysiol.,58, 569–572.
Cohen, D. (1968) Magnetoencephalography: evidence of magnetic fields produced by alpha rhythm currents.Science,161, 784–786.
de Munck, J. C., Dijk, B. W. andSpekreijse, H. (1988) Mathematical dipoles are adequate to describe realistic generators of human brain activity.IEEE Trans.,BME-35, 960–966.
Geddes, L. A. andBaker, L. E. (1967) The specific resistance of biological material—a compendium of data for the biomedical engineer and physiologist.Med. & Biol. Eng.,5, 271–293.
Grandori, F. (1982) Potential fields evoked by the peripheral auditory pathway: inverse solution.Int. J. Biomed. Comput.,13, 517–528.
He, B., Musha, T., Okamoto, Y., Homma, S., Nakajima, Y. andSato, T. (1987) Electric dipole tracing in the brain by means of the boundary element method and its accuracy.IEEE Trans.,BME-34, 406–414.
He, B., Musha, T., Ye, W., Nakajima, Y. andHomma, S. (1988) The dipole tracing method and its application to the human alpha wave. InEEG topography 1987. J.Tsuzui, J. (Ed.), Neuron Publishing Co. Ltd., 9–17.
He, B., Ye, W. andMusha, T. (1989) Equivalent dipole tracing of human alpha activities. Proc. 11th Ann. Int. Conf. IEEE Eng. in Med. & Biol. Soc., Seattle, 8th–12th Nov., 1217–1218.
Homma, S., Nakajima, Y., Musha, T., Okamoto, Y. andHe, B. (1987) Dipole-tracing method applied to human brain potentials.J. Neurosci. Meth.,21, 195–200.
Kavanagh, R. N., Darcey, T. M. andFender, D. H. (1976) The dimensionality of the human visual evoked scalp potential.Electroenceph. Clin. Neurophysiol.,40, 633–644.
Kosugi, Y., Ando, A., Ikebe, J. andTakahashi, H. (1985) Dipole localization of somatosensory evoked potentials in the brain.Jpn J. Med. Electron. & Biol. Eng.,23, 35–41.
Kowalik, J. andOsborne, M. R. (1968)Methods for unconstrained optimization problems. Elsevier, New York.
Lehmann, D., Ozaki, H. andPal, I. (1987) EEG alpha map series: brain micro-states by space-oriented adaptive segmentation.Electroenceph. Clin. Neurophysiol.,67, 271–288.
Lehmann, D. andMichel, C. M. (1989) Intracerebral dipole sources of EEG FFT power maps.Brain Topography,2, 155–164.
Meijs, J. W. H., ten Voorde, B. J., Peter, M. J., Stok, C. J. andLopes da Silva, F. H. (1988) On the influence of various models on the EEGs and MEGs. InFunctional brain map**. Pfurtsceller,G. andLopes da Silva, F. H. (Eds.).
Okamoto, Y., Teramachi, Y. andMusha, T. (1983) Limitation of the inverse problem in body surface potential map**.IEEE Trans.,BME-30, 749–754.
Plonsey, R. (1969)Bioelectric phenomena. McGraw-Hill, New York.
Witwer, J. G., Trezek, G. J. andJewett, D. L. (1972) The effect of media inhomogeneities upon intracranial electrical fields.IEEE Trans.,BME-19, 352–362.
Wood, C. C. (1982) Application of dipole localization methods to source identification of human evoked potentials. InEvoked potentials.Bodis-Wollner, I. (Ed.),Ann. N. Y. Acad. Sci.,388, 139–155.
Wood, C. C., Cohen, D., Coffin, B. N., Yarita, M. andAllison, T. (1985) Electrical sources in human somatosensory cortex: identification by combined magnetic and potential recordings.Science,227, 1051–1053.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
He, B., Musha, T. Equivalent dipole estimation of spontaneous EEG alpha activity: two-moving dipole approach. Med. Biol. Eng. Comput. 30, 324–332 (1992). https://doi.org/10.1007/BF02446971
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF02446971