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Anterior limbic alpha-like activity: a low resolution electromagnetic tomography study with lorazepam challenge.

Author(s): Connemann BJ, Mann K, Lange-Asschenfeldt C, Ruchsow M, Schreckenberger M, Bartenstein P, Grunder G

Affiliation(s): Department of Psychiatry III, University of Ulm, Leimgrubenweg 12, 89075 Ulm, Germany. bernhard.connemann@medizin.uni-ulm.de

Publication date & source: 2005-04, Clin Neurophysiol., 116(4):886-94. Epub 2005 Jan 18.

Publication type: Clinical Trial; Comparative Study ; Randomized Controlled Trial; Research Support, Non-U.S. Gov't

OBJECTIVE: To verify findings of an independently regulated anterior limbic alpha band source. METHODS: In a randomised cross-over study, the spontaneous EEG was recorded in nine healthy subjects after i.v. lorazepam or placebo. Intracerebral current densities within classical frequency bands were estimated with low resolution electromagnetic tomography [LORETA] and compared between groups with t-statistical parametric mapping [SPM[t]]. A region-of-interest [ROI] based method was used to compare frontal and occipital alpha band activity changes. RESULTS: Irrespective of treatment group, local maxima of alpha band power were localised both in the occipital lobe, Brodman area [BA] 18, and in the anterior cingulate cortex [ACC], BA 32. Statistical parametric mapping showed reduced parieto-occipital, but unaltered frontal alpha band power after lorazepam. This result was confirmed by ROI-based comparison of BA 18 and BA 32. CONCLUSIONS: There was an anterior limbic maximum of alpha band activity which, unlike occipital alpha, was not suppressed by lorazepam. SIGNIFICANCE: The well-known anterior alpha band components may originate from a narrowly circumscribed source, located in the ACC. Frontal and occipital alpha band activities appear to be independently regulated.

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