Brain mechanisms and hedonic processes.

This paper attempts to take a broad view of investigations of brain mechanisms of motivated and emotional behavior in animals and humans. It examines the thesis that the same basic brain mechanisms are involved in physiological regulations, in various motivated behaviors and emotions, and in the hedonic experiences that can be reported by humans. It further suggests that reward and the reinforcement of learning depend on the same brain systems. Finally, it speculates on the possibility that these same brain systems play an important role in the selection of what is learned and in the consolidation, storage, and retrieval of memory. To present this conceptualization, selected experiments in thermoregulatory behavior, electrical self-stimulation of the brain, evoked approach and withdrawal behaviors, and the role of neuropeptides in thirst and hunger are reviewed. In addition, experiments will be discussed in which memory is blocked by puromycin, but in which puromycin-induced amnesia can be prevented by the administration of certain peptides such as vasopressin and some of its fragments. Speculation about the common underlying mechanism and its biological significance in the adaptation of the organism is discussed as are some of the experiments suggested by this line of thinking.