title: Electromyographic activity in the EEG in Alzheimer's disease: noise or signal?
abstract: Many efforts have been directed at negating the influence of electromyographic (EMG) activity on the EEG, especially in elderly demented patients. We wondered whether these "artifacts" might reflect cognitive and behavioural aspects of dementia. In this pilot study, 11 patients with probable Alzheimer's disease (AD), 13 with amnestic mild cognitive impairment (MCI) and 13 controls underwent EEG registration. As EMG measures, we used frontal and temporal 50-70 Hz activity. We found that the EEGs of AD patients displayed more theta activity, less alpha reactivity, and more frontal EMG than controls. Interestingly, increased EMG activity indicated more cognitive impairment and more depressive complaints. EEG variables on the whole distinguished better between groups than EMG variables, but an EMG variable was best for the distinction between MCI and controls. Our results suggest that EMG activity in the EEG could be more than noise; it differs systematically between groups and may reflect different cerebral functions than the EEG.
authors.affiliation: Neuropsychology, Department of Neurology, Leiden University Medical Centre, P.O. Box 9600, 2300 RC Leiden, The Netherlands.
authors.forename: Karin
authors.initials: K
authors.lastname: van der Hiele
authors.forename: Robert H A M
authors.initials: RH
authors.lastname: Reijntjes
authors.forename: Alla A
authors.initials: AA
authors.lastname: Vein
authors.forename: Rudi G J
authors.initials: RG
authors.lastname: Westendorp
authors.forename: Mark A
authors.initials: MA
authors.lastname: van Buchem
authors.forename: Eduard L E M
authors.initials: EL
authors.lastname: Bollen
authors.forename: Huub A M
authors.initials: HA
authors.lastname: Middelkoop
authors.forename: J Gert
authors.initials: JG
authors.lastname: van Dijk