title: Looking for a precursor of spontaneous Sleep Slow Oscillations in human sleep: The role of the sigma activity.
abstract: Sleep Slow Oscillations (SSOs), paradigmatic EEG markers of cortical bistability (alternation between cellular downstates and upstates), and sleep spindles, paradigmatic EEG markers of thalamic rhythm, are two hallmarks of sleeping brain. Selective thalamic lesions are reportedly associated to reductions of spindle activity and its spectrum ~14 Hz (sigma), and to alterations of SSO features. This apparent, parallel behavior suggests that thalamo-cortical entrainment favors cortical bistability. Here we investigate temporally-causal associations between thalamic sigma activity and shape, topology, and dynamics of SSOs. We recorded sleep EEG and studied whether spatio-temporal variability of SSO amplitude, negative slope (synchronization in downstate falling) and detection rate are driven by cortical-sigma-activity expression (12-18Hz), in 3 consecutive 1s-EEG-epochs preceding each SSO event (Baselines). We analyzed: (i) spatial variability, comparing maps of baseline sigma power and of SSO features, averaged over the first sleep cycle; (ii) event-by-event shape variability, computing for each electrode correlations between baseline sigma power and amplitude/slope of related SSOs; (iii) event-by-event spreading variability, comparing baseline sigma power in electrodes showing an SSO event with the homologous ones, spared by the event. The scalp distribution of baseline sigma power mirrored those of SSO amplitude and slope; event-by-event variability in baseline sigma power was associated with that in SSO amplitude in fronto-central areas; within each SSO event, electrodes involved in cortical bistability presented higher baseline sigma activity than those free of SSO. In conclusion, spatio-temporal variability of thalamocortical entrainment, measured by background sigma activity, is a reliable estimate of the cortical proneness to bistability.
authors.affiliation: Department of Translational Research on New Technologies in Medicine and Surgery, University of Pisa, via Savi 10, 56126, Pisa, Italy.
authors.forename: Danilo
authors.initials: D
authors.lastname: Menicucci
authors.affiliation: Perceptual Robotics Laboratory, Scuola Superiore Sant'Anna, Pisa, via Alamanni 13b, 56010, Pisa, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Piarulli
authors.affiliation: EXTREME Centre, Institute of Life Sciences, Scuola Superiore Sant'Anna, Piazza Martiri della Libertà 33, 56127, Pisa, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Allegrini
authors.affiliation: EXTREME Centre, Institute of Life Sciences, Scuola Superiore Sant'Anna, Piazza Martiri della Libertà 33, 56127, Pisa, Italy.|Institute of Clinical Physiology, National Research Council (CNR), via Moruzzi 1, 56124, Pisa, Italy.
authors.forename: Remo
authors.initials: R
authors.lastname: Bedini
authors.affiliation: Perceptual Robotics Laboratory, Scuola Superiore Sant'Anna, Pisa, via Alamanni 13b, 56010, Pisa, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Bergamasco
authors.affiliation: EXTREME Centre, Institute of Life Sciences, Scuola Superiore Sant'Anna, Piazza Martiri della Libertà 33, 56127, Pisa, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Laurino
authors.affiliation: Department of Translational Research on New Technologies in Medicine and Surgery, University of Pisa, via Savi 10, 56126, Pisa, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Sebastiani
authors.affiliation: EXTREME Centre, Institute of Life Sciences, Scuola Superiore Sant'Anna, Piazza Martiri della Libertà 33, 56127, Pisa, Italy.|Institute of Clinical Physiology, National Research Council (CNR), via Moruzzi 1, 56124, Pisa, Italy.|Department of Surgical, Medical, Molecular and Critical Area Pathology, University of Pisa, via Savi 10, 56126, Pisa, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Gemignani
mesh_terms: D000293:Adolescent; D000328:Adult; D001683:Biological Clocks / Q000502:physiology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D005583:Fourier Analysis; D006801:Humans; D008297:Male; D012892:Sleep Deprivation; D012894:Sleep Stages / Q000502:physiology*; D013788:Thalamus / Q000502:physiology; D055815:Young Adult
keywords: Bistability; NREM sleep; Sigma band; Sleep slow oscillation; Spindle