The Human Brain:
The Structural Basis for Understanding Human Brain Function and Dysfunction

+++ INTERNATIONAL CONFERENCE +++ ROME +++ IRCCS SANTA LUCIA +++ Oct. 5-10, 2002 +++
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Helmut Laufs
Department of Neurology, Johann Wolfgang Goethe-Universität, Frankfurt am Main, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany
e-mail: h.laufs@em.uni-frankfurt.de

Poster Presentation:
CORTICAL MAPPING OF ALPHA RHYTHM USING COREGISTRATION OF CONTINUOUS AND SIMULTANEOUS EEG AND FMRI.
H Laufs, A Beyerle, E Eger, A Kleinschmidt, K Krakow
Department of Neurology, Johann Wolfgang Goethe-Universität, Frankfurt, Germany
Objective: EEG-correlated fMRI can be used to identify BOLD-signal changes associated with physiological or pathological EEG events. We used the technique of simultaneous and continuous EEG/fMRI to identify brain regions in which BOLD signal changes are associated with alpha (8-12 Hz) rhythm, the dominant EEG pattern of relaxed wakefulness. Method: In 5 female and 5 male subjects aged 31 +/- 3 yrs 32 channel EEG was recorded during eyes closed rest inside an MR scanner using an MR-compatible EEG recording system (BrainAmp MR, Brain Products, Munich, Germany). Imaging was performed on a Siemens Vision 1.5 T scanner using a continuous BOLD-fMRI sequence (TE/TR=50/0.8, 19x5 mm slices, FOV 220, 64x64 matrix) to acquire 300 scans/20 min. Offline pulse- and gradient artifact subtraction software was applied to obtain continuous EEG data also during fMRI-acquisition. Then, the average alpha power was calculated from electrode positions O1 and O2 (10/20 system) using a Fast Fourier Transformation. The alpha power was convolved with the hemodynamic response function and used as a regressor in SPM99. Results: The method presented provided valid EEG data during MR-image acquisition; alpha power of the EEG was not altered by pulse artifact subtraction. In all subjects fMRI activation maps showed a widespread negative correlation with the alpha power with one maximum over the parieto-occipital and another over the parieto-frontal cortex. Positive correlation was more variable between subjects. Conclusion: The negative correlation of alpha power with BOLD signal change may reflect a decreased neuronal activity in cortical areas generating alpha on scalp EEG.

 
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