title: Morning-evening variation in human brain metabolism and memory circuits.
abstract: It has been posited that a critical function of sleep is synaptic renormalization following a net increase in synaptic strength during wake. We hypothesized that wake would alter the resting-state functional organization of the brain and increase its metabolic cost. To test these hypotheses, two experiments were performed. In one, we obtained morning and evening resting-state functional MRI scans to assess changes in functional brain organization. In the second experiment, we obtained quantitative positron emission tomography measures of glucose and oxygen consumption to assess the cost of wake. We found selective changes in brain organization. Most prominently, bilateral medial temporal regions were locally connected in the morning but in the evening exhibited strong correlations with frontal and parietal brain regions involved in memory retrieval. We speculate that these changes may reflect aspects of memory consolidation recurring on a daily basis. Surprisingly, these changes in brain organization occurred without increases in brain metabolism.
authors.affiliation: Dept. of Radiology, Washington Univ, St. Louis, MO 63104, USA. bshannon@wustl.edu
authors.forename: B J
authors.initials: BJ
authors.lastname: Shannon
authors.forename: R A
authors.initials: RA
authors.lastname: Dosenbach
authors.forename: Y
authors.initials: Y
authors.lastname: Su
authors.forename: A G
authors.initials: AG
authors.lastname: Vlassenko
authors.forename: L J
authors.initials: LJ
authors.lastname: Larson-Prior
authors.forename: T S
authors.initials: TS
authors.lastname: Nolan
authors.forename: A Z
authors.initials: AZ
authors.lastname: Snyder
authors.forename: M E
authors.initials: ME
authors.lastname: Raichle
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D001921:Brain / Q000378:metabolism / Q000502:physiology*; D001931:Brain Mapping; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008568:Memory; D010101:Oxygen Consumption; D049268:Positron-Emission Tomography; D012890:Sleep
chemical_list: D001786:Blood Glucose