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Energetic basis of brain activity: implications for neuroimaging
Robert G Shulman1, Douglas L Rothman, Kevin L Behar
1Department of Diagnostic Radiology, Magnetic Resonance Research Center, Yale University School of Medicine, New Haven, CT 06510, USA. robert.shulan@yale.edu
Trends in Neurosciences
|July 24, 2004
Summary
The human brain is highly efficient, consuming 20% of body oxygen. Most brain energy supports neuronal firing and neurotransmitter cycling, even at rest, as shown by magnetic resonance spectroscopy (MRS) and fMRI.
Area of Science:
- Neuroscience
- Biophysics
- Metabolic research
Background:
- The human brain, 2% of body mass, consumes 20% of oxygen.
- Brain energy use and work are highly efficient processes.
- Neuronal activity and neurotransmitter cycling are key energy consumers.
Purpose of the Study:
- To investigate brain energy consumption and work efficiency.
- To quantify the contribution of neuronal firing and neurotransmitter cycling to brain energy use.
- To demonstrate ongoing cerebral activity even in resting states.
Main Methods:
- In vivo magnetic resonance spectroscopy (MRS) to track metabolic pathways.
- Monitoring glucose oxidation for energy production.
- Tracking glutamate and GABA neurotransmitter cycling for brain work.
- Functional magnetic resonance imaging (fMRI) to measure and localize neuronal activity.
Main Results:
- Approximately 80% of brain energy supports neuronal firing and GABA/glutamate cycling in the resting awake state.
- MRS and fMRI reveal significant ongoing cerebral activity.
- Small differences in neuronal activity are detectable between stimulation and control conditions.
Conclusions:
- The brain is remarkably efficient in its energy utilization.
- A substantial portion of brain energy expenditure is dedicated to neuronal function and neurotransmitter dynamics.
- Cerebral activity is continuous, even when the brain appears inactive.