A comparison of the localization of spontaneous neuromagnetic activity in the frequency and time domains.

We investigated the localization of current sources for spontaneous magnetoencephalographic data in the frequency and time domains. The two analysis techniques yielded complementary information about the underlying neuronal generators. Phase-coherent sources for occipital 10 Hz alpha band activity were identified in the frequency domain from the dependence of the equivalent current dipole strengths on the phase of the Fourier transform. Source localization in both the frequency and time domains was used to analyze data containing interictal spike and slow-wave activity. Predominantly 2-6 Hz spectral components localized in the frequency domain were found within an 8 cm3 volume centered at the time-domain source location of the spike. In general, the characteristics of the noise sources in magnetoencephalographic systems favor the use of frequency-domain analysis for rhythmic spontaneous activity.

[1]  R. Hari,et al.  Studies of auditory evoked magnetic and electric responses: Modality specificity and modelling , 1983 .

[2]  Matti Hämäläinen,et al.  Multichannel SQUID systems for brain research , 1991 .

[3]  R. Hari.  The neuromagnetic method in the study of the human auditory cortex , 1990 .

[4]  F. D. da Silva,et al.  Organization of thalamic and cortical alpha rhythms: spectra and coherences. , 1973, Electroencephalography and clinical neurophysiology.

[5]  R. Ilmoniemi,et al.  Selective localization of alpha brain activity with neuromagnetic measurements. , 1984, Electroencephalography and clinical neurophysiology.

[6]  H. Helmholtz.  Ueber einige Gesetze der Vertheilung elektrischer Ströme in körperlichen Leitern mit Anwendung auf die thierisch‐elektrischen Versuche , 1853 .

[7]  Toshimitsu Musha,et al.  Electric Dipole Tracing in the Brain by Means of the Boundary Element Method and Its Accuracy , 1987, IEEE Transactions on Biomedical Engineering.

[8]  T. Musha,et al.  Equivalent dipole tracing of human alpha activities , 1989, Images of the Twenty-First Century. Proceedings of the Annual International Engineering in Medicine and Biology Society,.

[9]  R. Ilmoniemi,et al.  Magnetoencephalography-theory, instrumentation, and applications to noninvasive studies of the working human brain , 1993 .

[10]  M. Scherg.  Fundamentals if dipole source potential analysis , 1990 .

[11]  C M Michel,et al.  Localization of the sources of EEG delta, theta, alpha and beta frequency bands using the FFT dipole approximation. , 1992, Electroencephalography and clinical neurophysiology.

[12]  B. Lütkenhöner.  Frequency-domain localization of intracerebral dipolar sources. , 1992, Electroencephalography and clinical neurophysiology.

[13]  Riitta Hari,et al.  Independence of steady-state 40-Hz response and spontaneous 10-Hz activity in the human auditory cortex , 1993, Brain Research.

[14]  K Reinikainen,et al.  [Physical basis of the generation of neuromagnetic fields]. , 1985, Biofizika.