text: The increased reliance of neurons on oxidative phosphorylation for energy facilitates the use of COX histochemistry in mapping regional brain metabolism in animals, since it establishes a direct and positive correlation between enzyme activity and neuronal activity. This can be seen in the correlation between COX enzyme amount and activity, which indicates the regulation of COX at the level of gene expression. COX distribution is inconsistent across different regions of the animal brain, but its pattern of its distribution is consistent across animals. This pattern has been observed in the monkey, mouse, and calf brain. One isozyme of COX has been consistently detected in histochemical analysis of the brain. Such brain mapping has been accomplished in spontaneous mutant mice with cerebellar disease such as reeler and a transgenic model of Alzheimer's disease. This technique has also been used to map learning activity in the animal brain.