Regional brain glucose metabolism during morning and evening wakefulness in humans: preliminary findings.
OBJECTIVE
The mechanisms that maintain wakefulness across the day, in the face in increasing sleep drive, are largely unknown. The goal of this pilot study was to examine regional relative brain glucose metabolism during morning and evening wakefulness in healthy humans.


METHODS
[18F]-fluorodeoxyglucose positron emission tomography scans were conducted during quiet wakefulness in the morning and in the evening. Statistical parametric mapping was used to compare relative regional glucose metabolism during the 2 scans. Subjects also completed subjective ratings of alertness.


METHODS
University of Pittsburgh General Clinical Research Center and Positron Emission Tomography Facility.


METHODS
Thirteen healthy adults (10 women, 3 men; mean age, 37 years)


METHODS
None.


RESULTS
Relative regional glucose metabolism was significantly higher in the evening than in the morning in a large cluster of midline and brainstem structures. Volumes of interest centered on the pontine reticular formation, midbrain reticular formation, midbrain raphe, locus coeruleus, and posterior hypothalamus also showed higher relative metabolism in the evening than in the morning. Relative glucose metabolism was significantly lower in the evening than in the morning in clusters that included structures in the right temporal cortex and occipital lobe, including cuneus and medial occipital gyrus.


CONCLUSIONS
Evening wakefulness is associated with increased relative metabolism in brainstem and hypothalamic arousal systems and decreased relative metabolism in posterior cortical regions. These patterns may reflect input from the circadian timing system to promote wakefulness, and/or the effects of increasing homeostatic sleep drive.
Buysse
Daniel J
DJ
Department of Psychiatry, University of Pittsburgh School of Medicine, University of Pittsburgh Medical Center, Pennsylvania, USA. buyssedj@upmc.edu
Nofzinger
Eric A
EA
Germain
Anne
A
Meltzer
Carolyn C
CC
Wood
Annette
A
Ombao
Hernando
H
Kupfer
David J
DJ
Moore
Robert Y
RY
D000328:Adult; D001143:Arousal / Q000502:physiology; D001786:Blood Glucose / Q000378:metabolism*; D001921:Brain / Q000000981:diagnostic imaging*; D001931:Brain Mapping; D002940:Circadian Rhythm / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D049268:Positron-Emission Tomography; D012016:Reference Values; D014851:Wakefulness / Q000502:physiology*
D001786:Blood Glucose; D019788:Fluorodeoxyglucose F18