Metabolic and hemodynamic events after changes in neuronal activity: current hypotheses, theoretical predictions and in vivo NMR experimental findings.
Unraveling the energy metabolism and the hemodynamic outcomes of excitatory and inhibitory neuronal activity is critical not only for our basic understanding of overall brain function, but also for the understanding of many brain disorders. Methodologies of magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) are powerful tools for the noninvasive investigation of brain metabolism and physiology. However, the temporal and spatial resolution of in vivo MRS and MRI is not suitable to provide direct evidence for hypotheses that involve metabolic compartmentalization between different cell types, or to untangle the complex neuronal microcircuitry, which results in changes of electrical activity. This review aims at describing how the current models of brain metabolism, mainly built on the basis of in vitro evidence, relate to experimental findings recently obtained in vivo by (1)H MRS, (13)C MRS, and MRI. The hypotheses related to the role of different metabolic substrates, the metabolic neuron-glia interactions, along with the available theoretical predictions of the energy budget of neurotransmission will be discussed. In addition, the cellular and network mechanisms that characterize different types of increased and suppressed neuronal activity will be considered within the sensitivity-constraints of MRS and MRI.
Mangia
Silvia
S
Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, Minnesota 55455, USA. mangia@cmrr.umn.edu
Giove
Federico
F
Tkác
Ivan
I
Logothetis
Nikos K
NK
Henry
Pierre-Gilles
PG
Olman
Cheryl A
CA
Maraviglia
Bruno
B
Di Salle
Francesco
F
Uğurbil
Kâmil
K
D000818:Animals; D001921:Brain / Q000098:blood supply / Q000378:metabolism* / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007773:Lactates / Q000378:metabolism; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008833:Microcirculation / Q000502:physiology; D008959:Models, Neurological; D009474:Neurons / Q000378:metabolism* / Q000502:physiology; D010084:Oxidation-Reduction; D012680:Sensitivity and Specificity; D009435:Synaptic Transmission / Q000502:physiology; D014664:Vasodilation / Q000502:physiology
D007773:Lactates; D005947:Glucose