Abstract
Functional connectivity networks are valuable tools for studying development, cognition, and disease in the infant brain. In adults, such networks are modulated by the state of consciousness and the circadian rhythm; however, it is unknown if infant brain networks exhibit similar variation, given the unique temporal properties of infant sleep and circadian patterning. To address this, we analyzed functional connectivity networks calculated from long-term EEG recordings (average duration 20.8 hr) from 19 healthy infants. Networks were subject specific, as intersubject correlations between weighted adjacency matrices were low. However, within individual subjects, both sleep and wake networks were stable over time, with stronger functional connectivity during sleep than wakefulness. Principal component analysis revealed the presence of two dominant networks; visual sleep scoring confirmed that these corresponded to sleep and wakefulness. Lastly, we found that network strength, degree, clustering coefficient, and path length significantly varied with time of day, when measured in either wakefulness or sleep at the group level. Together, these results suggest that modulation of healthy functional networks occurs over ∼24 hr and is robust and repeatable. Accounting for such temporal periodicities may improve the physiological interpretation and use of functional connectivity analysis to investigate brain function in health and disease.
Highlights
Measurements of functional connectivity in the infant brain can provide valuable insight into neural development, cognition, and disease
Functional connectivity networks are valuable tools for studying development, cognition, and disease in the infant brain. In adults, such networks are modulated by the state of consciousness and the circadian rhythm; it is unknown if infant brain networks exhibit similar variation, given the unique temporal properties of infant sleep and circadian patterning
AUTHOR SUMMARY In adults, functional connectivity networks are modulated by the state of consciousness and the circadian rhythm
Summary
Measurements of functional connectivity in the infant brain can provide valuable insight into neural development, cognition, and disease. EEG-based functional networks reflect the network segregation that occurs during prenatal development, with newborns exhibiting network hubs in the frontal and parieto-occipital lobes (Omidvarnia et al, 2014; Tóth et al, 2017). These networks evolve slowly throughout childhood, with unique frequency-specific connectivity for infants, toddlers, children, and adolescents (Chu et al, 2014). EEG-based functional networks are associated with cognitive functions, such as sustained infant attention (Xie, Mallin, & Richards, 2019), and network oscillations during sleep are correlated with motor, language, and social development in toddlers (Page, Lustenberger, & Fröhlich, 2018). As a marker of disease, functional connectivity analysis has been used to characterize infantile epilepsy (Shrey et al, 2018) and predict the onset of autism spectrum disorder (Righi et al, 2014)
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