Dense array EEG measures of infant sleep: microstructure and topography as biomarkers of cognitive development

The research presented here addresses topical and critical questions regarding the role of sleep as a facilitator of brain maturation and cognitive outcomes and examines how the topography and microstructure (i.e. sleep spindles and slow waves) of infant sleep brain rhythms may support these developmental processes. Although extensive research has been conducted on sleep in animal models, in adults and in premature neonates, very little is known about the neurophysiology of sleep in healthy human infants. Current research suggests that alterations in sleep pattern or duration play a role in almost all known mental disorders and furthermore, that virtually all of these disorders are rooted in a miswiring of the brain during development. Therefore, it is understandable that variability in sleep patterns has gained attention as a possible early biomarker for a number of neurodevelopmental disorders. Identification of reliable biomarkers could lead to targeted diagnostic tools that would be useful in diagnosing a number of developmental disorders. This dissertation is a first step toward a more comprehensive understanding of sleep microstructure (e.g. sleep spindles and slow waves), which is hypothesized to play a critical role in infant brain maturation. We have examined infant daytime sleep (non-rapid-eye-movement, NREM) in a rarely studied age group (3.5 and 6.5 months), using advanced dense-array electroencephalographic recording (dEEG) and analytic techniques seldom used in sleep studies, in combination with concurrent standardized assessments of cognition, language, and motor skill development. In this thesis, we have characterized spectral power and frequency changes of brain activity across the frequency spectrum (0.25-35Hz), in both a cross-sectional and a longitudinal group. From these analyses, we demonstrate that both maturational and trait-like aspects of regional NREM sleep oscillations are present in our sample of typically developing infants. Further, at 6.5 months-of-age, sleep spindle topography is sexually dimorphic, correlated with language measures, and functionally left-lateralized. In both the cross-sectional and longitudinal groups, and in both age ranges, there are significant positive and negative correlations of spectral power at different frequencies with differing behavioral measures. We anticipate that the outcomes of this ongoing study will accelerate our understanding of infant brain development across the first year of life, delineating the emergence, function and maturation of changing oscillatory sleep patterns, while simultaneously facilitating future translational approaches (e.g. interventional strategies for slow wave and spindle enhancement) targeting developmental sleep as it relates to the prevention of neuropsychiatric disorders.Ph.D.Includes bibliographical referencesby Suzanne E. Peter