title: Complex propagation patterns characterize human cortical activity during slow-wave sleep.
abstract: Cortical electrical activity during nonrapid eye movement (non-REM) sleep is dominated by slow-wave activity (SWA). At larger spatial scales (∼2-30 cm), investigated by scalp EEG recordings, SWA has been shown to propagate globally over wide cortical regions as traveling waves, which has been proposed to serve as a temporal framework for neural plasticity. However, whether SWA dynamics at finer spatial scales also reflects the orderly propagation has not previously been investigated in humans. To reveal the local, finer spatial scale (∼1-6 cm) patterns of SWA propagation during non-REM sleep, electrocorticographic (ECoG) recordings were conducted from subdurally implanted electrode grids and a nonlinear correlation technique [mutual information (MI)] was implemented. MI analysis revealed spatial maps of correlations between cortical areas demonstrating SWA propagation directions, speed, and association strength. Highest correlations, indicating significant coupling, were detected during the initial positive-going deflection of slow waves. SWA propagated predominantly between adjacent cortical areas, albeit spatial noncontinuities were also frequently observed. MI analysis further uncovered significant convergence and divergence patterns. Areas receiving the most convergent activity were similar to those with high divergence rate, while reciprocal and circular propagation of SWA was also frequent. We hypothesize that SWA is characterized by distinct attributes depending on the spatial scale observed. At larger spatial scales, the orderly SWA propagation dominates; at the finer scale of the ECoG recordings, non-REM sleep is characterized by complex SWA propagation patterns.
authors.affiliation: Department of Cellular and Network Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary. bhangya@cshl.edu
authors.forename: Balázs
authors.initials: B
authors.lastname: Hangya
authors.forename: Benedek T
authors.initials: BT
authors.lastname: Tihanyi
authors.forename: László
authors.initials: L
authors.lastname: Entz
authors.forename: Dániel
authors.initials: D
authors.lastname: Fabó
authors.forename: Loránd
authors.initials: L
authors.lastname: Erőss
authors.forename: Lucia
authors.initials: L
authors.lastname: Wittner
authors.forename: Rita
authors.initials: R
authors.lastname: Jakus
authors.forename: Viktor
authors.initials: V
authors.lastname: Varga
authors.forename: Tamás F
authors.initials: TF
authors.lastname: Freund
authors.forename: István
authors.initials: I
authors.lastname: Ulbert
mesh_terms: D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D058256:Brain Waves / Q000502:physiology*; D002540:Cerebral Cortex / Q000503:physiopathology*; D004569:Electroencephalography / Q000379:methods; D017029:Epilepsy, Complex Partial / Q000473:pathology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D009415:Nerve Net / Q000502:physiology; D017711:Nonlinear Dynamics; D012890:Sleep / Q000502:physiology*; D018709:Statistics, Nonparametric