Intrinsic connectivity network mapping in young children during natural sleep

Structural and functional neuroimaging have substantively informed the pathophysiology of numerous adult neurological and psychiatric disorders. While structural neuroimaging is readily acquired in sedated young children, pediatric application of functional neuroimaging has been limited by the behavioral demands of in-scanner task performance. Here, we investigated whether functional magnetic resonance imaging (fMRI) acquired during natural sleep and without experimental stimulation offers a viable strategy for studying young children. We targeted the lengthy epoch of non-rapid eye movement, stage 3 (NREM3) sleep typically observed at sleep onset in sleep-deprived children. Seven healthy, preschool-aged children (24-58 months) were studied, acquiring fMRI measurements of cerebral blood flow (CBF) and of intrinsic connectivity networks (ICNs), with concurrent sleep-stage monitoring. ICN data (T2* fMRI) were reliably obtained during NREM3 sleep; CBF data (arterial spin labeled fMRI) were not reliably obtained, as scanner noises disrupted sleep. Applying independent component analysis (ICA) to T2* data, distinct ICNs were observed which corresponded closely with those reported in the adult literature. Notably, a network associated with orthography in adults was not observed, suggesting that ICNs exhibit a developmental trajectory. We conclude that resting-state fMRI obtained in sleep is a promising paradigm for neurophysiological investigations of young children.