There appear to be three general aspects of emotional response. First, the perceptual or cortical aspect: the recognition of a situation as threatening, fearful, surprising, etc.; second, the physiological aspect: the pattern of changes in the respiratory, circulatory, muscular, and other body systems; third, the sensory aspect: the feeling-tone associated with the specific emotions of fear, anger, horror, etc. While there is general agreement on these aspects, there has been considerable disagreement as to the sequence of events in emotional response and the centers which control the process. Let us look at the leading theories.James-Lange Theory. In 1884 William James, and one year later the Danish physiologist Karl G. Lange, independently proposed a theory which conflicted with the common view of emotion. The accepted sequence of events was that we encounter a fierce-looking dog, feel frightened, and then leave with a beating heart. James and Lange, however, held that the correct order is (a) we meet the dog, (b) we experience the physiological reactions including the urge to run, and (c) these reactions generate the feeling of fright. These investigators maintained that our physical responses are the core of the emotion—or, as James put it, “We are afraid because we run; we do not run because we are afraid.” All these physical responses, visceral and skeletal alike, are mediated by the autonomic nervous system, and the feelings of the muscular tension (or relaxation), and especially the changes in our stomach and other internal organs, constitute the full emotion. Without them the emotion would not exist: “A disembodied emotion is a sheer nonentity.”The James-Lange theory led to a great deal of heated debate and, more importantly, to considerable research which has raised a number of crucial questions about it. First, it was found that the visceral organs are relatively insensitive to stimulation, and when they do respond, they react too slowly to account for the quickly occurring feelings of fear, anger, etc. Second, the few differences that can be found in the visceral patterns are insufficient to account for the wide variety of emotions we experience. Third, if visceral changes are artificially induced, for instance, through adrenalin injections, a full-blown emotion is not experienced; the subject simply feels that an emotion is coming on, but it never actually arrives. These findings have led many investigators to believe that there must be some central control of emotion, since the visceral and other peripheral factors do not tell the whole story.The Cannon-Bard Theory. A second major theory, proposed by Walter B. Cannon (1927) and elaborated by his pupil, Philip Bard, appeared to supply the “missing link.” It is sometimes referred to as the thalamic theory and sometimes as the hypothalamic theory, since it involves both of these structures. The hypothalamus is primarily concerned with the direct expression of emotion—for example, stimulation of this area in a cat has been found to produce rage reactions in the absence of any rage-producing situation. Moreover, cats showed emotional responses when the sympathetic nervous system was cut along the whole length of the spinal cord, thus depriving them of the usual autonomic responses. Cannon and Bard believed, further, that the thalamus controlled the experience of emotion, since it was the station on the way to the cortex. When external stimulation occurs, both of these centers, the hypothalamus and thalamus, become active at the same time, one accounting for emotional behavior and the other for emotional feeling or experience.Geldard (1962) points out that the Cannon-Bard theory arose from studies of lower animals whose feelings cannot be directly observed, while the James- Lange theory was created to explain precisely those feelings in man. He suggests that the two theories are concerned with different phenomena, or different aspects of the same process, and therefore neither one is a substitute for the other. The view that the hypothalamus is deeply involved with emotion has received strong support from many types of experiments. There is also evidence that portions of the thalamus are concerned with emotional reactions, and probably emotional experience as well, including anxiety, anger, and fear. However, as the following two theories indicate, the thalamus is by no means solely responsible for the experience of emotion.Lindsley’s Activity Theory was proposed shortly after the influence of the reticular formation on the arousal of the organism was demonstrated (1951).He accepted the view that the hypothalamus was the organizer of expressive behavior, but held that the reticular formation must be active before such behavior is at all possible. In other words, the organism must be tense and excited if it is to show the usual fear or anger responses—and if this structure is not aroused, it will be apathetic and unemotional. This has been demonstrated by studies of animals with damaged reticular systems. It has also been experimentally proved through the use of drugs that affect this structure. Schachter and Wheeler (1962), for example, gave groups of subjects placebos, adrenalin, and chlorpromazine. After this, they were shown an amusing film. The experimenters found that the group that had been given adrenalin, which activates the reticular formation, reacted boisterously, while the group given the placebo showed less reaction, and the group which had received the tranquilizer hardly reacted at all.The Lindsley theory recognizes that the hypothalamus, visceral and autonomic activities, cerebral cortex, and recticular formation are all involved in emotion. But its chief contribution, as Morgan (1965) puts it, is that it “integrates the reticular system, and the behavioral arousal accompanying its activity into the picture of brain mechanisms and emotion.” However, the theory may actually overemphasize the role of this system, since the hypothalamus has recently been found to have its own activating function through both the cerebral cortex and the autonomic nervous system, and has the effect of arousing the reticular formation itself (Gellhom, 1961).Papez-MacLean Theory. Originally proposed in 1937 by Papez, this theory brings another whole set of structures into the picture—that is, the hippocampus, fornix, mammillary bodies of the hypothalamus, and cingulate gyrus. These structures are all grouped together at the base of the brain, and were at one time thought to be concerned with the sense of smell. Papez, however, made the startling suggestion that they are all involved in emotion, and subsequent investigators have shown that they constitute a single system, which has become known as the limbic (“border”) system.Later, MacLean (1949, 1958) performed a number of experiments that seemed to support Papez’ theory, indicating that the limbic system may be the organizing center responsible for both emotional expression and emotional experience. It does not eliminate the hypothalamus, the autonomic nervous system, the reticular formation, or the cortex, but is believed to integrate all their activities. Many of the details of its function are still obscure, but in the opinion of Morgan as well as others, “the Papez-MacLean Theory is now much more than a theory. It is a general description of what experiment has established.”