title: Multiscale Lempel-Ziv complexity for EEG measures.
abstract: OBJECTIVE
  To demonstrate that the classical calculation of Lempel-Ziv complexity (LZC) has an important limitation when applied to EEGs with rapid rhythms, and to propose a multiscale approach that overcomes this limitation.
  
  
  METHODS
  We have evaluated, both with simulated and real EEGs, whether LZC calculation neglects functional characteristics of rapid EEG rhythms. In addition, we have proposed a procedure to obtain multiple binarization sequences that yield a spectrum of LZC, and we have explored whether complexity would be better captured using this computation.
  
  
  RESULTS
  In our simulated signals, classical LZC did not capture modulations of a rapid component when a slower component of more amplitude was included in the signal. In real EEGs from healthy participants with eyes closed and eyes open, classical LZC calculation failed to show any difference between these two conditions. However, a multiscale LZC showed that complexity was lower for eyes closed than for eyes open conditions.
  
  
  CONCLUSIONS
  As hypothesized, our new approximation captures the complexity of series with fast components masked by slower rhythms.
  
  
  CONCLUSIONS
  The method we introduce significantly improves LZC calculation, and it allows a better characterization of complexity of EEG signals.
authors.affiliation: Department of Psychology, University of Jaén, Spain. Electronic address: aibanez@ujaen.es.
authors.forename: Antonio J
authors.initials: AJ
authors.lastname: Ibáñez-Molina
authors.affiliation: Department of Psychology, University of Jaén, Spain.
authors.forename: Sergio
authors.initials: S
authors.lastname: Iglesias-Parro
authors.affiliation: Hospital San Agustín, Linares, Jaén, Spain.
authors.forename: María F
authors.initials: MF
authors.lastname: Soriano
authors.affiliation: Hospital San Agustín, Linares, Jaén, Spain.
authors.forename: José I
authors.initials: JI
authors.lastname: Aznarte
mesh_terms: D001921:Brain / Q000502:physiology*; D003198:Computer Simulation; D016208:Databases, Factual; D004569:Electroencephalography / Q000379:methods*; D006801:Humans
keywords: Complexity; EEG; Lempel–Ziv; Multiscale method