Cytochrome Oxidase Studies on the Human Visual Cortex

Publisher Summary In addition to positron emission tomography (PET) and magnetic resonance imaging (MRI) techniques, which detect brain activity in situ , metabolically active zones in the brain can also be gleaned by examining postmortem tissues reacted for an endogenous mitochondrial enzyme, cytochrome oxidase (CO). CO catalyzes the final step of oxidative metabolism, yielding ATP for diverse neuronal functions, notably the active maintenance of an ionic gradient across the electrically excitable membrane. Neuronal activity, which shifts this gradient, consumes energy and provides feedback regulation for oxidative enzymes, such as CO. Thereafter, CO serves as a sensitive metabolic marker for neuronal activity. Extensive studies in recent years have indicated that the pattern of cytochrome oxidase activity in the monkey visual cortex forms the basis for the parcellation of functional streams. The existence of a similar pattern in the human visual cortex lends support for comparable streams in human. The development and maturation of the CO pattern and, in particular, the CO-rich supragranular puffs of area 17 in man appear to lag behind that of the macaque monkey.