Brain Mechanisms

What are the chemical characteristics of brain mechanisms for aggression? Adams is to be complimented on a well-presented integration of behavioral and neurophysiological data on the brain mechanisms for offense, defense, and submission. Unlike the popular classification schemes, many of which were presented by nonexperimental, armchair theoreticians during the last decade, Adams's proposal is founded on his own experimental experience and that of others. The majority of the references and the largest amount of discussion is devoted to describing the brain mechanisms concerned with defensive behavior. And, in fact, most experimental work on neural mechanisms of "aggression" actually involves defense. Whatever caused Hess's observation of "affektive Abwehr" to be called "affective aggression"? Considerably less information is available on brain mechanisms of submissive behavior and even less on those Systems regulating offense.

Although it is difficult for me to present a critique, given that I am acknowledged by the author for earlier discussions of his ideas and sharing so many of his views, I offer the following four points:

1 The proposed outline of brain mechanisms regulating offense, defense, and submission follows the format and logic of traditional physiological psychology, composed basically of (1) sensory input. (2) "motivational" mechanisms, and (3) motor output ("patterning mechanisms" plus discrete acts, postures, and movements) with a few feedback and feedforward loops. Even if one accepts this type of flow of information as possible, a neural network subserving such functions has to be demonstrated. Most importantly, convincing identification of "motivational mechanisms," particularly that for offense, in the form of actual neural activity, has for the most part eluded investigators. I do not think that a single study in cats, reporting on four neurons active during "affective defense," is sufficient (although it is highly intriguing) evidence for a "motivational mechanism." Similarly, large-size destruction of midbrain structures and the subsequent observation of behavioral dysfunctions can hardly be considered cogent proof for motivational mechanisms. The postulated higher-function "motivational mechanisms" and "master switches." which ultimately determine whether movement A or B is exhibited, at present exist only as blocks in flow charts, not as "real" data.

2. Adams's neural circuitries describe mostly descending information flow. It is a great pity that he has chosen not to consider neurochemical and neuropharmacological data on anatomical systems as they relate to offense, defense, and submission. Many of the dopamine-, norepinephrine-, serotonin-, and GABA- containing pathways are ascending from mid- and hindbrain to subcortical and cortical terminations. There is, of course, a great deal of information relating the activity of these neurotransmitters to various modes of agonistic behavior (see, for recent reviews, Miczek and Barry 1976; Miczek and Krsiak 1979). The histochemical evidence suggests strongly that the brain structures portrayed in Adams's charts cannot be considered "functional anatomical units.' I think lesion and stimulation studies are of limited value in finding functional units. Describing behaviorally relevant neural networks in terms of anatomy as well as chemistry appears to be a prerequisite for modeling brain mechanisms.

3. Adams's distinction between submission and defense is, so far, the most convincing discussion of these modes of agonistic behavior. Yet, I am puzzled by the lack of discussion concerning flight. What is the relationship of submission and defense to flight? How is it possible to discuss submission and flight without reference to the form of social life characteristic for a particular animal species? For example, is submission prevalent in species that live in groups? And, do species whose members live a solitary adult life tend to rely on flight? The decision as to whether an organism engages in defense or submission is postulated to be made by a "consociate modulator" at the level of the ventromedial hypothalamus. An alternative view would predict that an organism exhibits defensive or submissive behavior mainly as a result of previous fighting experience and the intensity of the attack to which it is subjected.

4. Along with other authors. Adams emphasizes that a sensory comparator mechanism decides on the familiarity of a conspecific. If the comparator reads "unfamiliar," this signal becomes an important determinant for offense to occur. My own recent experimental experiences with mice, rats, and squirrel monkeys (Miczek 1978; 1979; Miczek and O'Donnell 1978) substantiate the great significance of the "stranger" as a proximal cause for offensive behavior. Yet, what are the releasing and directing stimuli for intragroup conflict? Offensive behavior toward a familiar conspecific or consort does occur even without apparent competition for food, mate, or shelter. The rather complex and multiple causes of fighting within established groups of rodents or primates appear largely ignored by Adams.