title: Loss of sleep spindle frequency deceleration in Obstructive Sleep Apnea.
abstract: OBJECTIVE
  Sleep spindles have been suggested as surrogates of thalamo-cortical activity. Internal frequency modulation within a spindle's time frame has been demonstrated in healthy subjects, showing that spindles tend to decelerate their frequency before termination. We investigated internal frequency modulation of slow and fast spindles according to Obstructive Sleep Apnea (OSA) severity and brain topography.
  
  
  METHODS
  Seven non-OSA subjects and 21 patients with OSA contributed with 30min of Non-REM sleep stage 2, subjected to a Matching pursuit procedure with Gabor chirplet functions for automatic detection of sleep spindles and quantification of sleep spindle internal frequency modulation (chirp rate).
  
  
  RESULTS
  Moderate OSA patients showed an inferior percentage of slow spindles with deceleration when compared to Mild and Non-OSA groups in frontal and parietal regions. In parietal regions, the percentage of slow spindles with deceleration was negatively correlated with global apnea-hypopnea index (rs=-0.519, p=0.005).
  
  
  CONCLUSIONS
  Loss of physiological sleep spindle deceleration may either represent a disruption of thalamo-cortical loops generating spindle oscillations or some compensatory mechanism, an interesting venue for future research in the context of cognitive dysfunction in OSA.
  
  
  CONCLUSIONS
  Quantification of internal frequency modulation (chirp rate) is proposed as a promising approach to advance description of sleep spindle dynamics in brain pathology.
authors.affiliation: Sleep Laboratory, Pulmonary Medicine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Brazil. Electronic address: diego.carvalho@ufrgs.br.
authors.forename: Diego Z
authors.initials: DZ
authors.lastname: Carvalho
authors.affiliation: Department of Physics and Chemistry, Universidade de Caxias do Sul, Brazil.
authors.forename: Günther J L
authors.initials: GJ
authors.lastname: Gerhardt
authors.affiliation: Sleep Laboratory, Pulmonary Medicine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Brazil.
authors.forename: Guilherme
authors.initials: G
authors.lastname: Dellagustin
authors.affiliation: Department of Physics, Universidade Federal de Sergipe, Brazil.
authors.forename: Emerson L
authors.initials: EL
authors.lastname: de Santa-Helena
authors.affiliation: Department of Physics and Biophysics, Institute of Biosciences, Universidade Estadual Paulista Julio de Mesquita Filho, Brazil.
authors.forename: Ney
authors.initials: N
authors.lastname: Lemke
authors.affiliation: Department of Neurology and Neurosciences, Weill Cornell Medical College, NY, USA.
authors.forename: Alan Z
authors.initials: AZ
authors.lastname: Segal
authors.affiliation: Sleep Laboratory, Pulmonary Medicine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Brazil.
authors.forename: Suzana V
authors.initials: SV
authors.lastname: Schönwald
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D058256:Brain Waves / Q000502:physiology*; D004569:Electroencephalography; D006801:Humans; D012890:Sleep / Q000502:physiology*; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*
keywords: Chirp; EEG; Matching pursuit; OSA; Sleep; Spindle