DYNAMIC UNCOUPLING AND RECOUPLING OF PERFUSION AND OXIDATIVE-METABOLISM DURING FOCAL BRAIN ACTIVATION IN MAN

Changes in glucose consumption, lactate production, and blood oxygenat ion were measured during prolonged neuronal activation (4-6 min) in hu man primary visual cortex using dynamic magnetic resonance spectroscop y and imaging, A decrease of steady-state glucose by 40% because of en hanced use by 21% was accompanied by a transient accumulation of lacta te with a peak value of 170% 2.5 min after stimulation onset, Rapid bl ood hyperoxygenation indicating ''uncoupling'' of blood flow and oxida tive metabolism was followed by a return to basal levels over 3 min, T hus, initial nonoxidative glucose consumption during functional activa tion is gradually complemented by a slower adjustment of oxidative pho sphorylation that ''recouples'' perfusion and oxygen consumption at a new equilibrium.