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Generalized Synchronization of MEG Recordings in Alzheimer’s Disease: Evidence for Involvement of the Gamma Band

Stam, Cornelis J.*‡; van Cappellen van Walsum, Anne Marie*‡; Pijnenburg, Yolande A. L.†‡; Berendse, Henk W.§; de Munck, Jan C.; Scheltens, Philip; van Dijk, Bob W.

Journal of Clinical Neurophysiology: December 2002 - Volume 19 - Issue 6 - p 562-574
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Summary The purpose of this study was to investigate interdependencies in whole-head magnetoencephalography (MEG) of Alzheimer patients and healthy control subjects. Magnetoencephalograms were recorded in 20 Alzheimer patients (11 men; mean age, 69.0 years [standard deviation, 8.2 years]); Mini-Mental State Examination score, 21.3 points; range, 15 to 27 points) and 20 healthy control subjects (9 men; mean age, 66.4 years [standard deviation, 9.0 years]) during a no-task eyes-closed condition with a 151 channel whole-head MEG system. Synchronization likelihood (a new measure for linear as well as nonlinear interdependencies between signals) and coherence were computed for each channel in different frequency bands (2 to 6, 6 to 10, 10 to 14, 14 to 18, 18 to 22, 22 to 40 Hz). Synchronization was lower in Alzheimer patients in the upper α band (10 to 14 Hz), the upper β band (18 to 22 Hz), and the γ band (22 to 40 Hz). In contrast, coherence did not show significant group differences at the p<0.05 level. The synchronization likelihood showed a spatial pattern (high synchronization central, parietal and right frontal; low synchronization, occipital and temporal). This study confirms a widespread loss of functional interactions in the α and β bands, and provides the first evidence for loss of γ band synchronization in Alzheimer’s disease. Synchronization likelihood may be more sensitive to detect such changes than the commonly used coherence analysis.

*Department of Clinical Neurophysiology; †Outpatient Clinic for Memory Disorders, Department of Neurology; ‡MEG Centre, and §Department of Neurology, VU University Medical Centre, Amsterdam, The Netherlands

Address correspondence and reprint requests to Dr. C. J. Stam, Professor of Clinical Neurophysiology, Department of Clinical Neurophysiology, VU University Medical Centre, PO Box 7057, 1007 MB Amsterdam, The Netherlands; e-mail: CJ.Stam@vumc.nl

Copyright © 2002 American Clinical Neurophysiology Society