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A coherent body of evidence supports the notion that sleep is a local and use-dependent process. Significant changes in brain morphology and function occur in the first years of life, revealing a postero-anterior trajectory of cortical maturation. On this basis, a recent study demonstrated that regional cortical maturation between early childhood and late adolescence is reflected in regional changes of sleep slow wave activity (SWA) during non-rapid eye movement (NREM) sleep. Our hypothesis is that changes of electroencephalogram (EEG) rhythms during sleep from birth to childhood are also mirrored by parallel regional changes in the EEG rhythms of sleep according to the assumption of a postero-anterior gradient in cortical maturation. We studied all-night EEG of 39 healthy, full-term, infants and children aged between 0 and 48 months, evaluating regional differences in NREM sleep. We confirmed the strictly local nature of sleep with frequency-specific regional differences. Specifically, we found a general shift of maxima of the upper alpha activity from occipital to prefrontal regions, expressed mainly by the ~11 Hz frequency. This shift corresponds to a postero-anterior trajectory of the so-called 'slow spindles'. The theta and alpha EEG activity of the frontal cortex exhibits a clear, positive, correlation with age. We conclude that specific local differences during NREM sleep, parallel cortical maturation also in the first 4 years of life., (© 2016 European Sleep Research Society.)

Study Objectives: To analyze sleep architecture of children with dyslexia, by means of conventional parameters and EEG spectral analysis and to correlate sleep parameters and EEG spectra with neuropsychological measures., Design: Cross-sectional study involving validated sleep questionnaires, neuropsychological scales, and polysomnographic recordings., Setting: Sleep laboratory in academic center., Participants: Sixteen subjects with developmental dyslexia (mean age 10.8 years) and 11 normally reading children (mean age 10.1 years). All the subjects underwent overnight polysomnographic recording; EEG power spectra were computed from the Cz derivation and spindle density was calculated during sleep stages N2., Intervention: N/A., Measurements and Results: Dyslexic children showed an increase in power of frequency bands between 0.5-3 Hz and 11-12 Hz in stage N2 and between 0.5-1 Hz in stage N3; they also showed significantly increased spindle density during N2. The power of the sigma band in N2 was positively correlated with the Word reading and MT reading tests; similarly, spindle density was significantly correlated with the Word reading test. The increased spindle activity and EEG sigma power in dyslexic subjects were found to be correlated with the degree of dyslexic impairment., Conclusions: The correlation found between sleep spindle activity and reading abilities in developmental dyslexia supports the hypothesis of a role for NREM sleep and spindles in sleep-related neurocognitive processing.

Objective: To analyze in detail the frequency content of the different EEG components of the Cyclic Alternating Pattern (CAP) in the whole sleep of pre-school and school age children compared to normal young adults., Methods: Fourteen pre-school age and 18 school age children and 16 adults were included in this study. Each participant underwent a polysomnographic overnight recording, after an adaptation night; sleep stages and CAP were scored following standard criteria. Average spectra were obtained for each CAP condition from the signal recorded from C3/A2 or C4/A1, separately in sleep stage 2 and slow-wave sleep (SWS), for each subject., Results: The analysis of the relative power density in the three groups showed that in sleep stage 2 and in SWS, CAP A1, A2, A3 subtypes had a significantly higher power in all frequency ranges in pre-school children than in adults, while school children differed mainly for the lower frequencies (<7 Hz). For non-CAP, pre-school and school children differed from adults at almost all frequencies analyzed. Generally, A1, A2 and A3 showed clear spectral differences in the three different groups of subjects with pre-school age children showing slightly less evident differences., Conclusions: CAP subtypes are characterized by clearly different spectra at different ages and also the same subtype shows a different power spectrum, during sleep stage 2 or SWS. This study shows that pre-school children have a different structure of sleep, especially from the microstructural (CAP) point of view: the differences are evident for all the CAP components and for non-CAP in almost all the frequency bands. This finding might be associated to the age-related delta decline in the 0-3 Hz frequency reported in children of the same age., Significance: Our data seem to provide information not available before and useful for the understanding of the impact of CAP on the sleep EEG neurophysiological dynamics at different ages. This type of information is crucial for a more adequate interpretation of data provided by a growing number of studies analyzing CAP in groups of pediatric patients.

Study Objectives: To analyze non-rapid eye movement (NREM) sleep microstructure of children with dyslexia, by means of cyclic alternating pattern (CAP) analysis and to correlate CAP parameters with neuropsychological measures., Design: Cross-sectional study using polysomnographic recordings and neuropsychological assessments., Setting: Sleep laboratory in academic center., Participants: Sixteen subjects with developmental dyslexia (mean age 10.8 years) and 11 normally reading children (mean age 10.1 years) underwent overnight polysomnographic recording., Intervention: N/A., Measurements and Results: Sleep architecture parameters only showed some statistically significant differences: number of sleep stage shifts per hour of sleep, percentage of N3, and number of R periods were significantly lower in dyslexic children versus controls. CAP analysis revealed a higher total CAP rate and A1 index in stage N3. A2% and A2 index in stage N2 and N3 were lower in dyslexic children while no differences were found for A3 CAP subtypes. The correlation analysis between CAP parameters and cognitive-behavioral measures showed a significant positive correlation between A1 index in N3 with Verbal IQ, full-scale IQ, and Memory and Learning Transfer reading test; while CAP rate in N3 was positively correlated with verbal IQ., Conclusions: To overcome reading difficulties, dyslexic subjects overactivate thalamocortical and hippocampal circuitry to transfer information between cortical posterior and anterior areas. The overactivation of the ancillary frontal areas could account for the CAP rate modifications and mainly for the increase of CAP rate and of A1 index in N3 that seem to be correlated with IQ and reading abilities.

Objective: To evaluate NREM sleep instability, as measured by the cyclic alternating pattern (CAP), in children with sleep terrors (ST) vs. normal controls., Methods: Ten boys (mean age: 8.5 years, range 5-13) meeting the following inclusion criteria: (a) complaint of ST several times a month, (b) a history of ST confirmed by a third person, and (c) a diagnosis of ST according to the ICSD-2 criteria. Eleven age-matched control children with parental report of at least 8.5h of nightly sleep, absence of known daytime consequences of sleep disorders were recruited by advertisement from the community. Sleep was visually scored for sleep macrostructure and CAP using standard criteria., Results: Sleep macrostructure showed only a significantly increased number of awakenings per hour and reduced sleep efficiency in ST subjects. CAP parameters analysis revealed several significant differences in ST vs. controls: an increase of total CAP rate in SWS, of A1 index in SWS and of the mean duration of A phases while B phases had a decreased duration, exclusively in SWS. The normalized CAP interval-distribution graphs showed significant differences in SWS with interval classes 10< or = i < 35s higher in children with ST and intervals classes above 50s higher in normal controls., Conclusions: Children with ST showed faster alternations of the amplitude of slow EEG bursts during SWS. This abnormally fast alternation of the EEG amplitude in SWS is linked to the frequent intrusion of CAP B phases interrupting the continuity of slow delta activity and could be considered as a neurophysiological marker of ST., Significance: This abnormal alternation of the EEG amplitude in SWS is associated with the occurrence of parasomnias and might be considered as a neurophysiological marker of disorders of arousal.