title: Spatial enhancement of EEG traces by surface Laplacian estimation: comparison between local and global methods.
abstract: OBJECTIVE
  Surface Laplacian estimation enhances EEG spatial resolution. In this paper, we compare, on empirical grounds, two computationally different estimations of the surface Laplacian.
  
  
  METHODS
  Surface Laplacian was estimated from the same monopolar data set with both Hjorth's method [local; Electroenceph Clin Neurophysiol 39 (1975) 526] as modified by MacKay [Electroenceph Clin Neurophysiol 56 (1983) 696] and with spherical spline interpolation [global; Electroenceph Clin Neurophysiol 72 (1989) 184].
  
  
  RESULTS
  The grand averages computed with the two methods proved to be very similar but differed markedly from the monopolar ones. The two different computations were highly correlated, presented low relative errors and allowed to evidence comparable experimental effects.
  
  
  CONCLUSIONS
  These results suggest that Hjorth's method and spherical spline interpolation convey similar topographic and chronometric informations.
  
  
  CONCLUSIONS
  We provide empirical evidence that local and global methods of surface Laplacian estimation are equivalent to improve the spatial resolution of EEG traces. Global methods allow to explore the scalp topography and local methods allow to spare time in electrode setting that can be useful for studies on special populations (i.e. children, aged subjects) and for clinical purposes.
authors.affiliation: Centre National de la Recherche Scientifique and Université de Provence, Laboratoire de Neurobiologie de la Cognition, CNRS-LNC, 31 chemin Joseph Aiguier, 13402 Marseille cedex 20, France. christophe.tandonnet@up.univ-mrs.fr
authors.forename: C
authors.initials: C
authors.lastname: Tandonnet
authors.forename: B
authors.initials: B
authors.lastname: Burle
authors.forename: T
authors.initials: T
authors.lastname: Hasbroucq
authors.forename: F
authors.initials: F
authors.lastname: Vidal
mesh_terms: D016477:Artifacts; D001931:Brain Mapping; D004566:Electrodes; D004569:Electroencephalography; D004576:Electromyography; D004585:Electrooculography / Q000379:methods; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008959:Models, Neurological; D011336:Probability; D011930:Reaction Time / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors