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Dynamics of EEG background activity level during quiet sleep in multiple nocturnal sleep episodes in infants
1Dipartimento di Teoria, Storia e Ricerca Sociale, Università di Trento, Italy. ifagioli@risc1.gelso.unitn.it
Insights
Infant EEG dynamics during sleep show internal organization within each sleep episode. A decreasing trend in synchronization rate across successive sleep episodes suggests early homeostatic sleep regulation in infants.
Area of Science:
- Neuroscience
- Sleep Science
- Developmental Biology
Background:
- Infant sleep architecture is complex and evolves rapidly during the first year of life.
- Previous research identified intra-sleep trends in EEG background activity within single sleep episodes.
- The study examines EEG dynamics across two distinct sleep episodes separated by wakefulness.
Purpose of the Study:
- To investigate EEG background activity dynamics during quiet sleep (QS) in infants.
- To determine if EEG dynamics exhibit similar intra-sleep trends in two successive nocturnal sleep episodes.
- To assess for progressive trends in EEG dynamics across two sleep episodes interrupted by waking.
Main Methods:
- Analysis of polygraphic recordings from two infant groups (9-15 weeks and 25-47 weeks old).
- Focus on the first two QS periods of two successive sleep episodes with natural interruptions.
- Computation of three EEG synchronisation indicators: parameter range, trough latency, and rate of synchronisation.
Main Results:
- All three EEG synchronisation indicators differed between the first and second QS periods within each sleep episode.
- The rate of synchronisation was higher in the first sleep episode compared to the second, indicating an across-night decrease.
- Parameter range and trough latency did not show significant across-night trends.
Conclusions:
- Infant sleep, even when fragmented, demonstrates internal EEG organization within each episode.
- An across-night decreasing trend in the rate of synchronisation emerges early in life.
- These findings suggest the early development of homeostatic sleep regulation mechanisms in infants.
Abstract:
The study reported in this paper investigated the dynamics of EEG background activity during quiet sleep (QS) in the first year of life. These dynamics have been previously shown to follow an intra-sleep trend within a single sleep episode, and the aim of this study was to show whether they were similar in two successive nocturnal sleep episodes interrupted by a waking episode, or whether they exhibited a progressive trend across the two episodes. The polygraphic recordings of two groups of 6 infants aged from 9 to 15 weeks old and from 25 to 47 weeks old, whose nocturnal sleep organisation was spontaneously interrupted, were selected. Three indicators of the time course of the parameter value, obtained from automatic analysis and reflecting the degree of synchronisation of the EEG activity recorded by the centro-occipital lead, were computed for the first two QS periods of two successive sleep episodes: the parameter range (difference between the EEG parameter value at the QS onset and that at the trough); the trough latency (time interval between QS onset and trough); and rate of synchronisation (range/trough latency). All 3 indicators differed between the first and the second QS period of both sleep episodes independently of age. The rate of synchronisation (but not the parameter range and the trough latency) was higher in the first sleep episode than in the second one, showing an over-night decreasing trend. Those results show that, when nocturnal sleep in infants is split into two episodes separated by an intervening waking, also the second sleep episode displays an internal organisation of its EEG dynamics. Moreover, an across-night trend in the rate of synchronisation can be observed from an early age, a finding which suggests, again, the early emergence of homeostatic regulation of sleep.