Animal MRI research addresses the pathophysiologic mechanisms underlying human brain disorders. The development of MRI techniques for transgenic mice allows for structural, metabolic, and functional assessments of the mouse brain at high spatial resolution. An observation of utmost importance is the high but reversible elevation of brain lactate in response to volatile anesthetics. The metabolite responses to various neuromodulators indicate a stimulation of adrenergic pathways as well as an inhibition of the respiratory chain. Corresponding findings in conditional Cox10 mutant mice, in which oligodendrocytes suffer from impaired oxidative energy metabolism, suggest the use of lactate as brain energy source, so that oligodendrocytes survive by enhanced nonoxidative glucose consumption which in turn secures the maintainance of myelin as well as long-term axonal integrity.