Brain Energetics and Neuronal Activity
Applications to fMRI and Medicine

Recent in vivo NMR studies of the brain have identified important metabolites and have measured their flows in animals and humans. 13C labeled molecules have been particularly important for these studies because the low 13C natural abundance allows labeled metabolites to stand out in NMR spectra.

Flows of labeled glucose into the glutamate, glutamine and GABA cerebral pools, measured by 13C NMR, establish the rate of glucose oxidation. In the same experiment, the rates of glutamate and GABA neurotransmitter release and recycling can be measured. Methods for performing these experiments and for interpreting the signals are described in this book, which provides the first integrated account of this rapidly growing field of functional, cerebral metabolism.

The thermodynamic relations between energy and work show that the brain efficiently uses its energy to support a high baseline level of neuronal activity in the absence of stimulation. These results lead to a proposed reformulation of fMRI experiments which have traditionally discarded the high baseline activity.

States of mind particularly, as they bear upon mental illness, have been correlated with in vivo concentrations of GABA, while the energy/neuronal firing results in epileptic patients have opened the energetic basis of this disease to study and understanding.

The quantitative, coherent picture emerging from these experiments solidifies our understanding of brain function and offers definite, novel insights into the processes of mental disorders.

Section A: Background.

1. Introduction (Douglas L. Rothman and Robert G. Shulman).

2. Energy Metabolism in Neural Tissues in vivo at Rest and in Functionally Altered States (Louis Sokoloff).

3. Techniques-MRS, fMRI, 13C NMR, Indirect Detection of 13C (Robin de Graaf).

4. Metabolic Modeling Analysis of Brain Metabolism (Graeme Mason).

Section B: Neuroenergetics and Activity.

5. Cerebral Energetics and Neurotransmitter Fluxes (Nicola R. Sibson).

6. NMR Studies of the Metabolism and Energetics of GABA Neurotransmitter Pathways (Kevin L. Behar and Douglas L. Rothman).

7. Neural Energy Consumption and the Representation of Mental Events (Simon B. Laughlin and David Attwell).

8. Imaging Cerebral Metabolic Rate of Oxygen Consumption (CMRO2) using 17O NMR Approach at Ultrahigh Field (Wei Chen, Xiao-Hong Zhu and Kamil Ugurbil).

9. Deriving Changes in CMRO2 from Calibrated fMRI (Fahmeed Hyder).

10. Relationship between CMRO2 and Neuronal Activity (Fahmeed Hyder and Hal Blumenfeld).

Section C: Clinical Beginnings.

11. NMR Studies of Bioenergetic Impairment in Human Epilepsy (Hoby P. Hetherington, Jullie W. Pan and Dennis D. Spencer).

12. MRS Studies of the Role of Altered Glutamate and GABA Neurotransmitter Metabolism in the Pathophysiology of Epilepsy (Ognen A. C. Petroff and Dennis D. Spencer).

13. The Role of Altered Energetics of Neurotransmitter Systems in Psychiatric Disease (Graeme F. Mason).

Section D: Brain and Mind.

14. Long-term Memory: Do Incremental Signals Reflect Engagement of Cognitive Processes? (Jed A. Meltzer and R. Todd Constable).

15. Using fMRI to Study the Mind and Brain (Bruce E. Wexler).

16. Brain and Mind: an NMR Perspective (Robert G. Shulman and Fahmeed Hyder).

17. The Role of the NMR Baseline Signal in the Study of Consciousness: the Restless Brain (Robert G. Shulman).

Index.