title: The localization of spontaneous brain activity: first results in patients with cerebral tumors.
abstract: OBJECTIVE
  From EEG studies, it is known that structural brain lesions are accompanied by abnormal rhythmic electric activity. With the better spatial resolution of MEG, MEG dipole analysis can extend the knowledge based on EEG power spectra. This study presents the first results of a completely automatic analysis method applied to spontaneous MEG.
  
  
  METHODS
  Spontaneous MEG data of 5 patients with cerebral brain tumors and 4 controls were collected using a whole-head MEG system. Signals were bandpass-filtered with cut-off frequencies according to standard EEG bands. A moving dipole model was fitted to samples with at least twice the average sample power. Dipoles explaining 90% or more of the magnetic variance were projected onto a matched MR scan.
  
  
  RESULTS
  In controls, dipole distributions are symmetrical with respect to the mid-sagittal plane whereas distributions in patients often are asymmetrical to it. Dipoles describing gamma activity were located contralateral, and dipoles describing delta and theta activity were located ipsilateral to lesions.
  
  
  CONCLUSIONS
  The automatic method gives plausible 3-dimensional information about generator foci of abnormal slow waves and other rhythms with respect to lesion foci and thereby adds physiological knowledge to that derived from EEG power spectra.
authors.affiliation: MEG Center, Academic Hospital Vrije Universiteit, The, Amsterdam, Netherlands. a.dejongh@azvu.nl
authors.forename: A
authors.initials: A
authors.lastname: de Jongh
authors.forename: J C
authors.initials: JC
authors.lastname: de Munck
authors.forename: J C
authors.initials: JC
authors.lastname: Baayen
authors.forename: E J
authors.initials: EJ
authors.lastname: Jonkman
authors.forename: R M
authors.initials: RM
authors.lastname: Heethaar
authors.forename: B W
authors.initials: BW
authors.lastname: van Dijk
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology*; D001932:Brain Neoplasms / Q000503:physiopathology*; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008875:Middle Aged; D012016:Reference Values