TECHNIQUE of electrical stimulation of subcortical structures developed by one of us (Hess *) is particularly suited to studies of the central organization of behavioral mechanisms. In the sequence of systematic investigations of the diencephalon and adjacent structures of the forebrain and mesencephalon (summarized by me13 in 1949) several thousand "points" were explored. The effects of electrical stimulation (cinematographically recorded) were correlated with the localizations of the needle tips (controlled by histological analysis). Among the various effects elicited were some, of particular note, which consisted of characteristic changes in the total attitude of the animals. The changes observed were best compared with alterations seen in emotional states of normal animals, such as fear, anger, and pleasure, or with certain drives, such as explorative tendencies, feeding tendencies, cleaning tendencies, and continuous restlessness. The question may arise here as to whether the described phenomena were accompanied by the subjective experience which is