Differences in sleep EEG coherence and spindle metrics in toddlers with and without receptive/expressive language delay: a prospective observational study

Abstract

Background: Changes in brain connectivity during development are thought to reflect organizational and maturational processes that correspond to skill acquisition in domains like motor, language, and cognition. This theory is supported by findings in typically developing children as well as observations of abnormal connectivity among children with neurodevelopmental differences. However, few coherence studies have capitalized on the potential of sleep electroencephalogram (EEG) to examine the developing brain, especially among very young children for whom formal neurodevelopmental diagnosis is not yet possible. Sleep microarchitecture in young children may offer key insights into neurophysiological abnormalities associated with neurodevelopmental trajectories and potentially aid in early detection and intervention. In this study, we explored sleep EEG coherence and sleep spindles in typically developing toddlers and toddlers at increased risk of later neurodevelopmental diagnoses.

Methods: We investigated EEG coherence and sleep spindles in 16 toddlers with receptive and expressive language delay (LangD) and 39 typically developing (TD) toddlers. Participants were aged 12-22 months at baseline, and 34 (LangD, n=11; TD, n=23) participants were evaluated again at 36 months of age.

Results: Average EEG coherence was stronger in the LangD group than the TD group, with differences most prominent during slow-wave sleep. Some age-related increases in coherence were observed, but these did not differ between groups. Sleep spindle density, duration, and frequency changed between baseline and follow-up for both groups, with the LangD group demonstrating a smaller magnitude of change than the TD group. The direction of change was frequency band-dependent for both groups.

Conclusions: These findings indicate that atypical sleep EEG connectivity and sleep spindle development can be detected in toddlers at risk of later neurodevelopmental diagnoses.

Trial registration: https://clinicaltrials.gov/study/NCT01339767 ; Registration date: 4/20/2011.

Keywords: Brain development; Cognitive function; Diagnostic markers; Language delay; Neurophysiology; Sleep architecture.