title: Suppression of deep brain stimulation artifacts from the electroencephalogram by frequency-domain Hampel filtering.
abstract: OBJECTIVE
  Currently, electroencephalography (EEG) cannot be used to record cortical activity during clinically effective DBS due to the presence of large stimulation artifact with components that overlap the useful spectrum of the EEG. A filtering method is presented that removes these artifacts whilst preserving the spectral and temporal fidelity of the underlying EEG.
  
  
  METHODS
  The filter is based on the Hampel identifier that treats artifacts as outliers in the frequency domain and replaces them with interpolated values. Performance of the filter was tested with a synthesized DBS signal and actual data recorded during bilateral monopolar DBS.
  
  
  RESULTS
  Mean increases in signal-to-noise ratio of 7.8dB for single-frequency stimulation and 13.8dB for dual-frequency stimulation are reported. Correlation analysis between EEG with synthesized artifacts and artifact-free EEG reveals that distortion to the underlying EEG in the filtered signal is negligible (r(2)>0.99).
  
  
  CONCLUSIONS
  Frequency-domain Hampel filtering has been shown to remove monopolar DBS artifacts under a number of common stimulation conditions used for the treatment of Parkinson's disease.
  
  
  CONCLUSIONS
  Application of frequency-domain Hampel filtering will allow the measurement of EEG in patients during clinically effective DBS and thus may increase our understanding of the mechanisms of action of this important therapeutic intervention.
authors.affiliation: Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL IL 60611,, USA. dp_allen@ieee.org
authors.forename: David P
authors.initials: DP
authors.lastname: Allen
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Stegemöller
authors.forename: Cindy
authors.initials: C
authors.lastname: Zadikoff
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Rosenow
authors.forename: Colum D
authors.initials: CD
authors.lastname: Mackinnon
mesh_terms: D016477:Artifacts; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping / Q000379:methods; D046690:Deep Brain Stimulation / Q000379:methods*; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D010300:Parkinson Disease / Q000503:physiopathology* / Q000628:therapy; D012815:Signal Processing, Computer-Assisted; D012984:Software