title: High frequency spectral components after secobarbital: the contribution of muscular origin--a study with MEG/EEG.
abstract: OBJECTIVE
  Previously we found that benzodiazepines not only provoke beta-activity in the EEG, but also higher frequency activity. Knowing the origin of this high frequency activity is crucial if localisation of epileptogenic brain tissue is the query. We attempt to differentiate cerebral from muscular origin of such activity.
  
  
  METHODS
  We postulate that EEG and MEG have similar sensitivity to brain activity, but different sensitivity to muscle activity, and compare co-recorded EEG and MEG signals in a group of five patients who had received short-lasting barbiturates to induce sleep. We performed principal components analysis over time and subtract the results for MEG from the EEG to see where the frequency spectra differ.
  
  
  RESULTS
  The EEG showed activity in the gamma bands up to 270Hz for all patients; the MEG significantly less. We find no differences in the lower frequency bands. Topographically the differences localized over the frontotemporal regions.
  
  
  CONCLUSIONS
  In the EEG benzodiazepines and/or barbiturates are not only associated with frequencies in the beta band, but also with wide range gamma activity. The latter seems to be of muscular origin.
  
  
  CONCLUSIONS
  Our study suggests that gamma activity in such measurements may not be cerebral in origin. MEG is less susceptible to contamination from muscle activity than the EEG.
authors.affiliation: Department of Clinical Neurophysiology, Stichting Epilepsy Instellingen Nederland, Epilepsy Institutes in The Netherlands, SEIN, Heemstede, The Netherlands. sclaus@sein.nl
authors.forename: Steven
authors.initials: S
authors.lastname: Claus
authors.forename: Demetrios
authors.initials: D
authors.lastname: Velis
authors.forename: Fernando H
authors.initials: FH
authors.lastname: Lopes da Silva
authors.forename: Max A
authors.initials: MA
authors.lastname: Viergever
authors.forename: Stiliyan
authors.initials: S
authors.lastname: Kalitzin
mesh_terms: D000328:Adult; D002648:Child; D004569:Electroencephalography / Q000187:drug effects* / Q000379:methods; D005260:Female; D006801:Humans; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D015225:Magnetoencephalography / Q000187:drug effects* / Q000379:methods; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000502:physiology; D012189:Retrospective Studies; D012631:Secobarbital / Q000494:pharmacology*; D055815:Young Adult
chemical_list: D006993:Hypnotics and Sedatives; D012631:Secobarbital