Mateusz Rusiniak, Monika Lewandowska, Agnieszka Pluta, Katarzyna Ciesla, Joanna Wojcik, Tomasz Wolak
(Bioimaging Research Center, World Hearing Center of the Institute of Physiology and Pathology of Hearing, Warszawa/Kajetany, Poland)
JHS 2015; 5(2): OA16-22
The aim of the present work is to investigate the relationship between spontaneous electroencephalographic (EEG) brain activity at 8–13 Hz frequency (Berger’s rhythm) and thalamus activation. The leading theory of how Berger’s rhythm is generated suggests a thalamo–occipital circuit, but there is still much uncertainty as to the role of the thalamus.
MATERIAL AND METHODS: We used a Siemens Magnetom 3T Trio scanner and a 64-channel NeuroScan SynAmps2 EEG system to examine 36 healthy young male adults. The study paradigm consisted of 30-s blocks with eyes closed alternated with 30-s blocks with eyes open, both repeated six times. The EEG data was preprocessed as follows: 1) fMRI gradient artifact removal; 2) BCG reduction; 3) 1–20 Hz band-pass filtration. Alpha rhythm segments were marked in the preprocessed data. fMRI data was preprocessed using typical procedures (motion correction, normalization, smoothing), and then a general linear model (GLM) analysis was performed using alpha segments derived from the EEG as events. A modified hemodynamic response function suitable for examining thalamus physiology was applied.
RESULTS: EEG data produced a typical spatial distribution of the alpha rhythm, mostly elicited in the parieto–occipital electrodes. Group-level analysis of the fMRI data failed to reveal any activation in the thalamus. However, further investigation revealed three subgroups of patients: 1) those who had a signal decrease in the left medial dorsal nucleus; 2) those with positive activation of thalamic structures; and 3) those where no activation was detected in the thalamus.
CONCLUSIONS: The thalamus might be involved differently in alpha rhythm generation from one subject to another. The observed intersubject variability might be caused by physiological mechanisms underlying Berger’s rhythm.
Keywords: Alpha Rhythm, Electroencephalography, Magnetic Resonance Imaging, Thalamus