Density and frequency caudo-rostral gradients of sleep spindles recorded in the human cortex.
OBJECTIVE
This study aims at providing a quantitative description of intrinsic spindle frequency and density (number of spindles/min) in cortical areas using deep intracerebral recordings in humans.


METHODS
Thirteen patients suffering from pharmaco-resistant focal epilepsy and investigated through deep intracortical EEG in frontal, parietal, temporal, occipital, insular, and limbic cortices including the hippocampus were included.


METHODS
Spindle waves were detected from the ongoing EEG during slow wave sleep (SWS) by performing a time-frequency analysis on filtered signals (band-pass filter: 10-16 Hz). Then, spindle intrinsic frequency was determined using a fast Fourier transform, and spindle density (number of spindles per minute) was computed.


RESULTS
Firstly, we showed that sleep spindles were recorded in all explored cortical areas, except temporal neocortex. In particular, we observed the presence of spindles during SWS in areas such as the insular cortex, medial parietal cortex, occipital cortex, and cingulate gyrus. Secondly, we demonstrated that both spindle frequency and density smoothly change along the caudo-rostral axis, from fast frequent posterior spindles to slower and less frequent anterior spindles. Thirdly, we identified the presence of spindle frequency oscillations in the hippocampus and the entorhinal cortex.


CONCLUSIONS
Spindling activity is widespread among cortical areas, which argues for the fundamental role of spindles in cortical functions. Mechanisms of caudo-rostral gradient modulation in spindle frequency and density may result from a complex interplay of intrinsic properties and extrinsic modulation of thalamocortical and corticothalamic neurons.
Service de Neurologie Fonctionnelle et d’Epileptologie, Hôpital Neurologique, Centre Hospitalier Est, 59 Boulevard Pinel, Bron, France. laure.peter@chu-lyon.fr
Laure
L
Peter-Derex
Jean-Christophe
JC
Comte
François
F
Mauguière
Paul A
PA
Salin
D000293:Adolescent; D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology*; D004569:Electroencephalography; D018728:Entorhinal Cortex / Q000502:physiology / Q000503:physiopathology; D004828:Epilepsies, Partial / Q000503:physiopathology; D005260:Female; D006624:Hippocampus / Q000502:physiology / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012890:Sleep / Q000502:physiology*; D012894:Sleep Stages / Q000502:physiology; D055815:Young Adult