In this chapter we examine higher mental function in the brain, and the developmental processes which influence them. Environmental factors operate in three major areas: 1) information input via the sensory and perceptual systems, 2) information organization, and 3) behavioral output. Developmental and environmental factors which affect brain information in each of these areas is reviewed with the intent of acquainting the reader with the major principles of brain-behavior organization. In the final section we discuss the physiological alterations in brain function as it relates to major clinical syndromes.