Cortical and Subcortical Correlates of Electroencephalographic Alpha Rhythm Modulation

Bernd Feige, Klaus Scheffler, Fabrizio Esposito, Francesco Di Salle, Jürgen Hennig, Erich Seifritz
2005 Journal of Neurophysiology  
Neural correlates of electroencephalographic (EEG) alpha rhythm are poorly understood. Here, we related EEG alpha rhythm in awake humans to blood-oxygen-leveldependent (BOLD) signal change determined by functional magnetic resonance imaging (fMRI). Topographical EEG was recorded simultaneously with fMRI during an open versus closed eyes and an auditory stimulation versus silence condition. EEG was separated into spatial components of maximal temporal independence using independent component
more » ... ysis. Alpha component amplitudes and stimulus conditions served as general linear model regressors of the fMRI signal time course. In both paradigms, EEG alpha component amplitudes were associated with BOLD signal decreases in occipital areas, but not in thalamus, when a standard BOLD response curve (maximum effect at ϳ6 s) was assumed. The part of the alpha regressor independent of the protocol condition, however, revealed significant positive thalamic and mesencephalic correlations with a mean time delay of ϳ2.5 s between EEG and BOLD signals. The inverse relationship between EEG alpha amplitude and BOLD signals in primary and secondary visual areas suggests that widespread thalamocortical synchronization is associated with decreased brain metabolism. While the temporal relationship of this association is consistent with metabolic changes occurring simultaneously with changes in the alpha rhythm, sites in the medial thalamus and in the anterior midbrain were found to correlate with short time lag. Assuming a canonical hemodynamic response function, this finding is indicative of activity preceding the actual EEG change by some seconds. Downloaded from FIG. 5. Left: conjunction analysis between protocol (eyes open/closed) and orthogonalized alpha at lag 0 (x/y/z slice coordinates: ϩ6 Ϫ17 ϩ 8 mm, whole brain correction, only positive correlation); right: correlation with (protocol-orthogonalized) alpha amplitude at lag 0 for the auditory paradigm (slice coordinates: ϩ2 Ϫ14 ϩ 11 mm, small volume correction, only positive correlation, voxel threshold P Ͻ 0.001). 2870 FEIGE ET AL.
doi:10.1152/jn.00721.2004 pmid:15601739 fatcat:o7gnby75nvfcfnbys5esp3eala