title: Synchronization and Propagation of Global Sleep Spindles.
abstract: Sleep spindles occur thousands of times during normal sleep and can be easily detected by visual inspection of EEG signals. These characteristics make spindles one of the most studied EEG structures in mammalian sleep. In this work we considered global spindles, which are spindles that are observed simultaneously in all EEG channels. We propose a methodology that investigates both the signal envelope and phase/frequency of each global spindle. By analysing the global spindle phase we showed that 90% of spindles synchronize with an average latency time of 0.1 s. We also measured the frequency modulation (chirp) of global spindles and found that global spindle chirp and synchronization are not correlated. By investigating the signal envelopes and implementing a homogeneous and isotropic propagation model, we could estimate both the signal origin and velocity in global spindles. Our results indicate that this simple and non-invasive approach could determine with reasonable precision the spindle origin, and allowed us to estimate a signal speed of 0.12 m/s. Finally, we consider whether synchronization might be useful as a non-invasive diagnostic tool.
authors.affiliation: Departamento de Física e Biofísica, UNESP - Univ. Estadual Paulista, Botucatu, Brazil.
authors.forename: Rafael Toledo Fernandes de
authors.initials: RT
authors.lastname: Souza
authors.affiliation: Departamento de Física e Química da Universidade de Caxias do Sul, Caxias do Sul, Brazil.
authors.forename: Günther Johannes Lewczuk
authors.initials: GJ
authors.lastname: Gerhardt
authors.affiliation: Hospital de Clínicas de Porto Alegre (HCPA), Neurology and Pulmonology Sections, Porto Alegre, Brazil.
authors.forename: Suzana Veiga
authors.initials: SV
authors.lastname: Schönwald
authors.affiliation: Departamento de Física e Biofísica, UNESP - Univ. Estadual Paulista, Botucatu, Brazil.
authors.forename: José Luiz
authors.initials: JL
authors.lastname: Rybarczyk-Filho
authors.affiliation: Departamento de Física e Biofísica, UNESP - Univ. Estadual Paulista, Botucatu, Brazil.
authors.forename: Ney
authors.initials: N
authors.lastname: Lemke
mesh_terms: D000328:Adult; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012890:Sleep / Q000502:physiology*