title: Sleep affects cortical source modularity in temporal lobe epilepsy: A high-density EEG study.
abstract: OBJECTIVE
  Interictal epileptiform discharges (IEDs) constitute a perturbation of ongoing cerebral rhythms, usually more frequent during sleep. The aim of the study was to determine whether sleep influences the spread of IEDs over the scalp and whether their distribution depends on vigilance-related modifications in cortical interactions.
  
  
  METHODS
  Wake and sleep 256-channel electroencephalography (EEG) data were recorded in 12 subjects with right temporal lobe epilepsy (TLE) differentiated by whether they had mesial or neocortical TLE. Spikes were selected during wake and sleep. The averaged waking signal was subtracted from the sleep signal and projected on a bidimensional scalp map; sleep and wake spike distributions were compared by using a t-test. The superimposed signal of sleep and wake traces was obtained; the rising phase of the spike, the peak, and the deflections following the spike were identified, and their cortical generator was calculated using low-resolution brain electromagnetic tomography (LORETA) for each group.
  
  
  RESULTS
  A mean of 21 IEDs in wake and 39 in sleep per subject were selected. As compared to wake, a larger IED scalp projection was detected during sleep in both mesial and neocortical TLE (p<0.05). A series of EEG deflections followed the spike, the cortical sources of which displayed alternating activations of different cortical areas in wake, substituted by isolated, stationary activations in sleep in mesial TLE and a silencing in neocortical TLE.
  
  
  CONCLUSIONS
  During sleep, the IED scalp region increases, while cortical interaction decreases.
  
  
  CONCLUSIONS
  The interaction of cortical modules in sleep and wake in TLE may influence the appearance of IEDs on scalp EEG; in addition, IEDs could be proxies for cerebral oscillation perturbation.
authors: Department of Neuroscience - SNPSRR, University of Padua, Padua, Italy. Electronic address: alessandra.delfelice@unipd.it.
authors: Alessandra
authors: A
authors: Del Felice
authors: Department of Computer Science, University of Verona, Strada le Grazie 15, Verona, Italy.
authors: Silvia Francesca
authors: SF
authors: Storti
authors: Department of Neurological and Movement Sciences, Section of Neurology, University of Verona, Piazzale L.A. Scuro 10, Verona, Italy; Department of Neurophysiology, Foundation IRCCS San Camillo Hospital, Via Alberoni 70, Venezia-Lido, Italy.
authors: Paolo
authors: P
authors: Manganotti
mesh_terms: D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D004569:Electroencephalography / Q000379:methods*; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012890:Sleep / Q000502:physiology*; D013702:Temporal Lobe / Q000502:physiology*; D055815:Young Adult
keywords: Brain oscillatory rhythms; Electrical source imaging (ESI); Epileptogenic zone; Interictal epileptiform discharge (IED); Perturbational approach