Our knowledge of how the brain functions has markedly improved in recent years, but this improvement has largely been constrained to simpler levels of processing such as those involved in sensory or motor systems. In contrast, the neural bases of higher functions such as consciousness, will, long-term planning, complex problem- solving, etc., are still under investigation, although everyone agrees that the frontal lobes (FL) play an important role in such processes. The importance of understanding these neural bases of higher functions becomes even more evident in the study of aging, since a decrease of frontal lobe perfusion is reported during aging, and because this age-related frontal lobe dysfunction has been proposed to explain part of the cognitive disorders (attention disorders, decreased mental flexibility and abstraction) and behavioral changes (mainly apathy or indifference) associated with aging.