Brain Mechanisms

The traditional opinion that one can often distinguish between affective defense and flight as two separate but related behavioral systems in the cat is not questioned by the Blanchards, nor do they deny my proposal that this reflects the differences between defense and submission. They do question one of my quotations, however, from Baxter (1967). Baxter's results are open to several alternative explanations, as the author himself pointed out. On the one hand, the different behavioral effects of electrical and chemical stimulation may have taken place upon two separate neural systems near the site of chemical stimulation, as I have chosen to interpret the data. On the other hand, the chemical stimulation may have taken place at a remote site, which was a "hypothesis" considered by the author and raised by the Blanchards to the level of "almost certainly." In any case, Baxter himself concluded that his data support the case of different neural substrates for escape, on the one hand, and attack and threat, on the other. I relate these systems to submission and defense, respectively.

Finally, my analysis of the function of forebrain structures in the rat is questioned by the Blanchards, The crux of my analysis deals with the ventromedial hypothalamus as a structure that facilitates submission and inhibits defense. With this they do not quarrel, except to point out correctly that the evidence from Veening (1975) is very weak because the behavior is so poorly described. With regard to the septum, they cite new data recently published from their laboratory, which they consider to support a unitary concept of defense rather than a distinction between defense and submission (Blanchard, Blanchard, Lee, and Nakamura 1979). I am not convinced. Whereas the motor patterns characteristic of defense, such as lunge-and-bite, boxing, and jumping, were all greatly increased following septal lesions, the two motor patterns characteristic of submission did not increase in most cases and sometimes did not appear at all. Rates of full submissive posture were not mentioned, presumably because they remained very low. And rates of ultrasonic vocalization were paradoxical. On the first day of experiment 1 and the preshock tests of experiment 2 they were elevated, but on the other days of experiment 1 they were, if anything, decreased, and on the postshock tests of experiment 2 they were not reliably different from controls, despite continued elevations in rates of defense motor patterns. The appearance of ultrasound at all is inconsistent with the simple model that I present in the final figure, but as I point out in the last paragraph in the section on submission and show with dotted lines in Figure 3, there is evidence that septal lesions not only affect the hypothetical consociate modulator, but also disinhibit the forebrain afferent pathway for both defense and submission without involving the consociate modulator (see Albert commentary).

The role of the septum in aggressive behavior is very complex, as indicated in the target article. In muroid rodents it appears to facilitate the consociate modulator, which can explain why lesions release the lunge-and-bite attack. But, as noted above in discussing the Blanchard critique, it may also have a tonic inhibitory effect upon the forebrain defense pathway, so that lesions may also disinhibit inputs for both submission and defense and stimulation may directly suppress defense. Furthermore, septal lesions may affect offense behaviors. Adding to the complications, the effects of septal lesions on defense are transitory and may not be observed at all in some species such as the mouse, opossum, and primates. Although septal lesions occasionally enhance defense-in- the cat (see, e.g., Spiegel, Miller, and Oppenheimer 1940, quoted in the target article), they have also failed to enhance defense in the cat in other studies, such as the one that Ursin has performed, which he mentions in his commentary.

Part of the complication may be related to the fact that the septum is a complex structure and lesions may involve a number of different neural systems; thus, Albert, who has studied the matter in detail, notes in his commentary that the most effective site for lesions that enhance defense is not in the septum itself, but ventral to the lateral septum. Another aspect of the complication is the time course of lesion effects; thus Yutzey mentions the fact that after rats recover from the initial period of hyperdefensiveness caused by septal lesions, they show a curious behavior called "contact-seeking" in which they approach other animals, including predators, and seem to be in a state of abnormal "fearlessness" (Meyer, Ruth, and Lavond 1978). It would appear that following an initial period in which the function of the consociate modulator is depressed there follows a rebound period in which it is overactive and even predators are treated like consociates. Finally, Yutzey asks if I consider the septal syndrome (i.e., the initial hyperdefensiveness following septal lesions) to represent natural behavioral repertoires. The answer is yes, since I point out in the target article that "although the lesion-induced defense is excessive in comparison to that of laboratory rats and house cats, it may appear normal if compared to that of wild-trapped rats and feral cats."

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