Due to their non-stationarity, ERP signals are difficult to study. The concept of cointegration might overcome this problem and allow for the study of the co-variability between whole ERP signals. In this context cointegration factor is defined as the ability of an ERP signal to co-vary with other ERP signals. The aim of the present study was to investigate whether the cointegration factor is dependent on different EMF conditions and gender, as well as the locations of the electrodes on the scalp. The findings revealed that women have a significantly higher cointegration factor than men, while all subjects have increased cointegration factors in the presence of EMF. The cointegration factor is location dependent, creating a distinct cluster of high coin- tegration capacity at the central and lateral electrodes of the scalp, in contrast to clusters of low cointegration capacity at the anterior and posterior electrodes There seem to be distinct similarities of the present findings with those from standard methodologies of the ERPs. In conclusion cointegration is a promising tool towards the study of functional interactions between different brain locations.
KeywordsEMFERPStationarityCointegrationACF
Fabiani, M., Gratton, G. and Coles, M. (2000) Event- related potentials: Methods, theory and applications. Handbook of Psychophysiology, 3rd Edition. Cambridge University Press, New York.
Laufs, H., Kleinschmidt, A., Beyerle, A., Eger, E., Salek-Haddadi, A., Preibisch, C. and Krakow, K. (2003) EEG-correlated fMRI of human alpha activity. NeuroImage, 19(4), 1463-1476.
Papageorgiou, C.C., Nanou, E.D., Tsiafakis, V.G., Capsalis, C.N. and Rabavilas, A.D. (2004) Gender related differences on the EEG during a simulated mobile Phone signal. Neuroreport, 15(16), 2557-2560.
Agam, Y. and Sekuler, R. (2007) Interactions between working memory and visual perception: An ERP/EEG study. NeuroImage, 36(3), 933-942.
Edwards, E., Soltani, M., Deouell, L.Y., Berger, M.S. and Knight, R.T. (2005) High gamma activity in response to deviant auditory stimuli recorded directly from human cortex. Journal of Neurophysiology, 94, 4269-4280.
Yordanova, J., Rosso, O.A. and Kolev, V. (2003) A transient dominance of theta event-related brain potential component characterizes stimulus processing in an auditory oddball task. Clinical Neurophysiology, 114(3), 529- 540.
Quiroga, R.Q., Sakowitz, O.W., Basar, E. and Schürmann, M. (2001) Wavelet Transform in the analysis of the frequency composition of evoked potentials. Brain Research Protocols, 8(1), 16-24.
Chlubnová, J., Kremláček, J., Kubová, Z. and Kuba, M. (2005) Visual evoked potentials and event related potentials in congenitally deaf subjects. Physiological Research, 54, 577-583.
Sanders, L.D., Newport, E.L. and Neville, H.J. (2002) Segmenting nonsense: An event-related potential index of perceived onsets in continuous speech. Nature Neuroscience, 5, 700-703.
Shibata, T., Shimoyama, I., Ito, T., Abla, D., Iwasa, H., Koseki, K., Yamanouchi, N., Sato, T. and Nakajima, Y. (1998) The synchronization between brain areas under motor inhibition process in humans estimated by event-related EEG coherence. Neuroscience Research, 31(4), 265-271.
Hauk, O., Davis, M.H., Ford, M., Pulvermüller, F. and Marslen-Wilson, W.D. (2006) The time course of visual word recognition as revealed by linear regression analysis of ERP data. NeuroImage, 30(4), 1383-1400.
Nikolaev, A.R., Ivanitsky, G.A., Ivanitsky, A.M., Posner, M.I. and Abdullaev, Y.G. (2001) Correlation of brain rhythms between frontal and left temporal (Wernicke’s) cortical areas during verbal thinking. Neuroscience Letters, 298(2), 107-110.
Oya, H., Poon, P.W.F., Brugge, J.F., Reale, R.A., Kawasaki, H., Volkov, I.O. and Howard III, M.A. (2007) Functional connections between auditory cortical fields in humans revealed by Granger causality analysis of intra-cranial evoked potentials to sounds: Comparison of two methods. Biosystems, 89, 198-207.
Engle, R. and Granger, C.W. (1987) Co-integration and error correction representation estimation and testing. Econometrica, 55(2), 251-276.
Yang, K. and Shahabi, C. (2005) On the stationarity of multivariate time series for correlation-based data analysis. Proceedings of the Fifth IEEE International Conference on Data Mining, 805-808.
Brandt, M.E., Ademoglu, A. and Pritchard, W.S. (2000) Non-linear prediction and complexity of alpha EEG activity. International Journal of Bifurcation and Chaos, 10(1), 123-133.
Wechsler, D. (1955) Manual for the Wechsler adult intelligence scale. Psychological Corporation, New York.
Jasper, H.H. (1958) The ten-twenty electrode system of the international federation. Electroencephalography and Clinical Neurophysiology, 10, 371-375.
Newey, W.K. and West, K.D. (1987) A simple, positive semi-definite, heteroskedasticity and autocorrelation consistent covariance matrix. Econometrica, 55(3), 703-708.
Kwiatkowski, D., Phillips, P.C.B., Schmidt, P. and Shin, Y. (1991) Testing the null hypothesis of stationarity against the alternative of a unit root. How sure are we that economic time series have a unit root? Journal of econometrics, 54, 158-178.
Hobijn, B., Franses, P.H. and Ooms, M. (2004) Generalizations of the KPSS-test for stationarity. Statistica Neerlandica, 58(4), 483-502.
Granger, C.W. and Newbold, P. (1974) Spurious regression in econometrics. Journal of Econometrics, 2(2), 111- 120.
Dolado, J.J., Gonzalo, J. and Marmol, F. (2009) A Companion to Theoretical Econometrics, In: Baltagi, B.H., Ed., Blackwell Reference Online, 634-654 http://www.blackwellreference.com/public/book?id=g9781405106764_9781405106764
Croft, R.J., Chandler, J.S., Burgess, A.P., Barry, R.J., Williams, J.D. and Clarke, A.R. (2002) Acute Mobile phone operation affects neural function in humans. Clinical Neurophysiology, 113(10), 1623-1632.
Curcio, G., Ferrara, M., Moroni, F., D'Inzeo, G., Bertini, M. and De Gennaro, L. (2005) Is the brain influenced by a phone call? An EEG study of resting wakefulness. Neuroscience Research, 53(3), 265-270.
Hamblin, D.L., Wood, A.W., Croft, R.J. and Stough, C. (2004) Examining the effects of electromagnetic fields emitted by GSM mobile phones on human event-related potentials and performance during an auditory task. Clinical Neurophysiology, 115(1), 171-178.
Krause, C.M., Björnberg, C.H., Pesonen, M., Hulten, A., Liesivuori, T., Koivisto, M., Revonsuo, A., Laine, M. and Hämäläinen, H. (2006) Mobile phone effects on children's event-related oscillatory EEG during an auditory memory task. International Journal of Radiation Biology, 82(6), 443-450.
Challis, L.J. (2005) Mechanisms for interaction between RF fields and biological tissue. Bioelectromagnetics, Supplement 7 Review, 26, 98-106.
Valentini, E., Curcio, G., Moroni, F., Ferrara, M., De Gennaro, L. and Bertini, M. (2007) Neurophysiological effects of mobile phone electromagnetic fields on humans: A comprehensive review. Bioelectromagnetics, 28, 415-432.
Hamblin, D.L., Croft, R.J., Wood, A.W., Stough, C. and Spong, J. (2006) The sensitivity of human event-related potentials and reaction time to mobile phone emitted electromagnetic fields. Bioelectromagnetics, 27, 265-273.
Yuasa, K., Arai, N., Okabe, S., Tarusawa, Y., Nojima, T., Hanajima, R., Terao, Y. and Ugawa, Y., (2006) Effects of thirty minutes mobile phone use on the human sensory cortex. Clinical Neurophysiology, 117(4), 900-905.
Skrandies, W., Reik, P. and Kunze, C. (1999) Topography of evoked brain activity during mentalarithmetic and language tasks: sex differences. Neuropsychologia, 37(4), 421-430.
Briere, M.E., Forest, G., Chouinard, S. and Godbout, R. (2003) Evening and morning EEG differences between young men and women adults. Brain and Cognition, 53(2), 145-148.
Dimpfel, W., Wedekind, W. and Keplinger, I. (2003) Gender difference in electrical brain activity during presentation of various film excerpts with different emotional content. European Journal of Medical Research, 8(5), 192-198.
Razumnikova, O.M. and Vol'f, N.V. (2007) Gender differences in interhemisphere interactions during distributed and directed attention. Neuroscience and Behavioral Physiology, 37(5), 429-434.
Barry, R.J., Clarke, A.R., McCarthy, R., Selikowitz, M., Johnstone, S.J. and Rushby, J.A. (2004) Age and effects in EEG coherence: I. Developmental trends in normal children. Clinical Neurophysiology, 115(10), 2252-2258.
Haarala, C., Aalto, S., Hautzel, H., Julkunen, L., Rinne, J.O., Laine, M., Krause, B. and Hämäläinen, H. (2003) Effects of a 902 MHz mobile phone on cerebral blood flow in humans: a PET study. Neuroreport, 14(16), 2019- 2023.
Cinel, C., Boldini, A., Russo, R. and Fox, E. (2007) Effects of mobile phone electromagnetic fields on an auditory order threshold task. Bioelectromagnetics, 28(6), 493- 496.