Structural brain correlates of human sleep oscillations

Sleep is strongly conserved within species, yet marked and perplexing inter-individual differences in sleep physiology are observed. Combining EEG sleep recordings and high-resolution structural brain imaging, here we demonstrate that the morphology of the human brain offers one explanatory factor of such inter-individual variability. Gray matter volume in interoceptive and exteroceptive cortices correlated with the expression of slower NREM sleep spindle frequencies, supporting their proposed role in sleep protection against conscious perception. Conversely, and consistent with an involvement in declarative memory processing, gray matter volume in bilateral hippocampus was associated with faster NREM sleep spindle frequencies. In contrast to spindles, gray matter volume in the homeostatic sleep-regulating center of the basal forebrain/hypothalamus, together with the medial prefrontal cortex, accounted for individual differences in NREM slow wave oscillations. Together, such findings indicate that the qualitative and quantitative expression of human sleep physiology is significantly related to anatomically specific differences in macroscopic brain structure. (C) 2013 Elsevier Inc. All rights reserved.