Diurnal changes in human brain glutamate + glutamine levels in the course of development and their relationship to sleep

• Published in: NeuroImage (Orlando, Fla.) Vol. 196; pp. 269 - 275
• Main Authors: Volk, Carina, Jaramillo, Valeria, Studler, Mirjam, Furrer, Melanie, O'Gorman Tuura, Ruth L., Huber, Reto
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-08-2019; Elsevier Limited
• Subjects: Adolescent; Adult; Adults; Age; Alcohol; Brain - anatomy & histology; Brain - growth & development; Brain - metabolism; Caffeine; Child; Children; Children & youth; Circadian Rhythm; Circadian rhythms; Cortex; Cortical plasticity; Diurnal; EEG; Electroencephalography; Female; Glutamic Acid - metabolism; Glutamine; Glutamine - metabolism; GLX; Gray Matter - anatomy & histology; High-density EEG; Humans; Magnetic resonance spectroscopy; Male; Metabolism; Metabolites; MRS; Neural plasticity; Neuroimaging; NMR; NREM sleep; Nuclear magnetic resonance; REM sleep; Scanners; Sleep; Spectrum analysis; Substantia grisea; Teenagers; Young Adult; High-density EEG; GLX; Cortical plasticity; MRS
• ISSN: 1053-8119; 1095-9572
• DOI: 10.1016/j.neuroimage.2019.04.040

Sleep slow waves during non-rapid eye movement (NREM) sleep play a crucial role in maintaining cortical plasticity, a process that is especially important in the developing brain. Children show a considerably larger overnight decrease in slow wave activity (SWA; the power in the EEG frequency band between 1 and 4.5 ​Hz during NREM sleep), which constitutes the primary electrophysiological marker for the restorative function of sleep. We previously demonstrated in adults that this marker correlates with the overnight reduction in cortical glutamate ​+ ​glutamine (GLX) levels assessed by magnetic resonance spectroscopy (MRS), proposing GLX as a promising biomarker for the interplay between cortical plasticity and SWA. Here, we used a multimodal imaging approach of combined MRS and high-density EEG in a cross-sectional cohort of 46 subjects from 8 to 24 years of age in order to examine age-related changes in GLX and its relation to SWA. Gray matter volume, GLX levels and SWA showed the expected age-dependent decrease. Unexpectedly, the overnight changes in GLX followed opposite directions when comparing children to adults. These age-related changes could neither be explained by the overnight decrease in SWA nor by circadian factors.
•Brain metabolite overnight changes were assessed by magnetic resonance spectroscopy.•The change in glutamate ​+ ​glutamine (GLX) was larger in adults than in children.•The overnight change in GLX did not correlate with the main EEG markers of sleep.•The time of day influence on GLX levels should be considered differently across age.