The thalamus as the generator and modulator of EEG alpha rhythm: a combined PET/EEG study with lorazepam challenge in humans.
BACKGROUND
Purpose of this study was to investigate the functional relationship between electroencephalographic (EEG) alpha power and cerebral glucose metabolism before and after pharmacological alpha suppression by lorazepam.


METHODS
Ten healthy male volunteers were examined undergoing two F18-fluorodeoxyglucose (18-FDG) positron emission tomography (PET) scans with simultaneous EEG recording: 1x placebo, 1x lorazepam. EEG power spectra were computed by means of Fourier analysis. The PET data were analyzed using SPM99, and the correlations between metabolism and alpha power were calculated for both conditions.


RESULTS
The comparison lorazepam versus placebo revealed reduced glucose metabolism of the bilateral thalamus and adjacent subthalamic areas, the occipital cortex and temporo-insular areas (P < 0.001). EEG alpha power was reduced in all derivations (P < 0.001). Under placebo, there was a positive correlation between alpha power and metabolism of the bilateral thalamus and the occipital and adjacent parietal cortex (P < 0.001). Under lorazepam, the thalamic and parietal correlations were maintained, whereas the occipital correlation was no longer detectable (P < 0.001). The correlation analysis of the difference lorazepam-placebo showed the alpha power exclusively correlated with the thalamic activity (P < 0.0001).


CONCLUSIONS
These results support the hypothesis of a close functional relationship between thalamic activity and alpha rhythm in humans mediated by corticothalamic loops which are independent of sensory afferences. The study paradigm could be a promising approach for the investigation of cortico-thalamo-cortical feedback loops in neuropsychiatric diseases.
Schreckenberger
Mathias
M
Department of Nuclear Medicine, Johannes Gutenberg-University Mainz, 55131 Mainz, Germany. schreckenberger@nuklear.klinik.uni-mainz.de
Lange-Asschenfeldt
Christian
C
Lange-Asschenfeld
Christian
C
Lochmann
Matthias
M
Mann
Klaus
K
Siessmeier
Thomas
T
Buchholz
Hans-Georg
HG
Bartenstein
Peter
P
Gründer
Gerhard
G
D000328:Adult; D000513:Alpha Rhythm / Q000187:drug effects* / Q000379:methods*; D014151:Anti-Anxiety Agents / Q000494:pharmacology; D001921:Brain / Q000000981:diagnostic imaging / Q000187:drug effects / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D006801:Humans; D008140:Lorazepam / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009778:Occipital Lobe / Q000187:drug effects / Q000378:metabolism; D010296:Parietal Lobe / Q000187:drug effects / Q000378:metabolism; D013788:Thalamus / Q000187:drug effects / Q000378:metabolism; D014055:Tomography, Emission-Computed / Q000379:methods
D014151:Anti-Anxiety Agents; D005947:Glucose; D008140:Lorazepam