Energetic basis of brain activity: implications for neuroimaging.
The complex activities of the brain need not distract us from the certainty that it uses energy and performs work very efficiently. The human brain, which claims approximately 2% of our body mass, is responsible for approximately 20% of our body oxygen consumption. In vivo magnetic resonance spectroscopy (MRS) follows the metabolic pathways of energy production (as glucose oxidation) and work (as monitored by the cycling of glutamate and GABA neurotransmitters). In the resting awake state, approximately 80% of energy used by the brain supports events associated with neuronal firing and cycling of GABA and glutamate neurotransmitters. Small differences in neuronal activity between stimulation and control conditions can be measured and localized using functional magnetic resonance imaging (fMRI). MRS and fMRI experiments show that the majority of cerebral activity, which is often disregarded in imaging experiments, is ongoing even when the brain appears to be doing nothing.
Shulman
Robert G
RG
Department of Diagnostic Radiology, Magnetic Resonance Research Center, Yale University School of Medicine, New Haven, CT 06510, USA. robert.shulan@yale.edu
Rothman
Douglas L
DL
Behar
Kevin L
KL
Hyder
Fahmeed
F
D000818:Animals; D001481:Basal Metabolism / Q000502:physiology; D001931:Brain Mapping; D002247:Carbon Isotopes / Q000378:metabolism; D002540:Cerebral Cortex / Q000166:cytology / Q000000981:diagnostic imaging* / Q000378:metabolism*; D002952:Citric Acid Cycle / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology*; D018698:Glutamic Acid / Q000378:metabolism*; D006801:Humans; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D009474:Neurons / Q000000981:diagnostic imaging / Q000378:metabolism; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000378:metabolism; D051381:Rats; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D002247:Carbon Isotopes; D019275:Radiopharmaceuticals; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid