PHYSICAL SUBSTRATA OF MENTAL ENERGY - BRAIN CAPACITY AND EFFICIENCY OF CEREBRAL METABOLISM

The traditional psychometric construct of intelligence is linked to me ntal energy which, in turn, is related to the capacity of the central nervous system (CNS) - i.e. the number of functioning neurons in the b rain. This article reviews the evidence from studies of fluid intellig ence, aging and diabetes mellitus which indicates that another propert y of the CNS-neural efficiency-provides an alternative physical basis of mental energy. The presence of nonoxidative metabolic processes in the brain indicates that a cognitive task has reached the limits of co mplexity for a given individual. It is suggested that the physical sub strata of mental energy involve both the capacity and the efficiency o f the CNS.