title: Scalp electrical recording during paralysis: quantitative evidence that EEG frequencies above 20 Hz are contaminated by EMG.
abstract: OBJECTIVE
  To identify the possible contribution of electromyogram (EMG) to scalp electroencephalogram (EEG) rhythms at rest and induced or evoked by cognitive tasks.
  
  
  METHODS
  Scalp EEG recordings were made on two subjects in presence and absence of complete neuromuscular blockade, sparing the dominant arm. The subjects undertook cognitive tasks in both states to allow direct comparison of electrical recordings.
  
  
  RESULTS
  EEG rhythms in the paralysed state differed significantly compared with the unparalysed state, with 10- to 200-fold differences in the power of frequencies above 20 Hz during paralysis.
  
  
  CONCLUSIONS
  Most of the scalp EEG recording above 20 Hz is of EMG origin. Previous studies measuring gamma EEG need to be re-evaluated.
  
  
  CONCLUSIONS
  This has a significant impact on measurements of gamma rhythms from the scalp EEG in unparalysed humans. It is to be hoped that signal separation methods will be able to rectify this situation.
authors.affiliation: Department of Neurology, Flinders University and Medical Centre, GPO Box 2100, Adelaide, SA 5042, Australia.
authors.forename: Emma M
authors.initials: EM
authors.lastname: Whitham
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Pope
authors.forename: Sean P
authors.initials: SP
authors.lastname: Fitzgibbon
authors.forename: Trent
authors.initials: T
authors.lastname: Lewis
authors.forename: C Richard
authors.initials: CR
authors.lastname: Clark
authors.forename: Stephen
authors.initials: S
authors.lastname: Loveless
authors.forename: Marita
authors.initials: M
authors.lastname: Broberg
authors.forename: Angus
authors.initials: A
authors.lastname: Wallace
authors.forename: Dylan
authors.initials: D
authors.lastname: DeLosAngeles
authors.forename: Peter
authors.initials: P
authors.lastname: Lillie
authors.forename: Andrew
authors.initials: A
authors.lastname: Hardy
authors.forename: Rik
authors.initials: R
authors.lastname: Fronsko
authors.forename: Alyson
authors.initials: A
authors.lastname: Pulbrook
authors.forename: John O
authors.initials: JO
authors.lastname: Willoughby
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D016477:Artifacts; D004569:Electroencephalography; D004576:Electromyography; D006801:Humans; D008297:Male; D008606:Mental Processes; D009466:Neuromuscular Blocking Agents; D010243:Paralysis / Q000175:diagnosis / Q000503:physiopathology* / Q000523:psychology; D010775:Photic Stimulation; D012535:Scalp / Q000503:physiopathology*
chemical_list: D009466:Neuromuscular Blocking Agents