Brain Mechanisms of Aggressive Behavior; An Updated Review
Behavioral Descriptions Page 4

Title page & Abstract
Page 1

Page 2

Page 3

Behavioral Descriptions
Page 4

Motivational Mechanisms
Page 5

Defense Motivational Mechanism
Pages 6-7

Offense Motivational Mechanism
Page 8

Interactions &
Hormone Effects

Page 9

Relations in Hypothalamus
Page 10

Sensory Analyzers of Offense & Patrol/Marking
Page 11

Sensory Analyzers of Familiarity
Page 12

Sensory Analyzers of Defense
Pages 13-14

Motor Patterning Mechanisms
Page 15

Sensory Analyzers for Releasing & Directing Stimuli
Page 16

Testing the Model
Page 17

Acknowledgements & References
Pages 18-19-20-21-22-23-24-25

The motivational systems model described in this review is based on the descriptions of the behaviors of over 20 species of muroid rodents (Adams, 1980) and a comparison to the behavior of primates (Adams, 1981) as well as the behavior of cats (Leyhausen, 1956).

Offense and defense behaviors are two forms of aggressive behavior, shown by one member of a species against another, unlike predatory aggression. In the muroid rodents, they are most easily distinguished by their different motor patterns of attack and the orientation of locomotion (Adams, 1980). Offense involves approach locomotion and the bite-and-kick attack, in which the attacker jumps or lies across the back of the opponent and bites the opposite flank. Defense involves freezing or flight locomotion and the lunge-and-bite attack which is directed at the face or other protruding part of the opponent. In actual practice, the offensive and defensive animals may be distinguished by the patterns of wounding suffered during fighting. The defensive animal is usually wounded on the flank and rump as a result of bite-and-kick attacks by its opponent, while the offensive animal (if wounded at all) is often bitten on the face as a result of lunge-and-bite attack by its opponent. Furthermore, the offensive animal is characterized by confident approach towards its opponent or chasing if the encounter takes place outside or in a large arena. Locomotion of the defensive animal is characterized by escape attempts and flight locomotion if there is an opportunity for escape, although the lunge-and-bite attack includes a limited rapid approach lunge. In the muroid rodents, defense also includes a wide range of vocalizations and other sounds.

Although under most circumstances the behavior of muroid rodents is dominated by one motivation at a time, ie, they are primarily offensive or defensive, there is one important exception: the lactating female. In our experience with R norvegicus, lactating females show a combination of the attack behaviors of both offense and defense. In this regard, it should be noted that several motor patterns are shared by offense, defense and patrol-marking and have been called "ambivalent acts or postures"; these include approach locomotion which is activated by either offense or patrol/marking, and the sideways and upright postures which can be activated by both offense and defense (Grant and Mackintosh, 1963; Lehman and Adams, 1977).

In muroid rodents, the behaviors of patrol-marking are those of dominant males who periodically and systematically make the rounds of their territories, investigating scents and scent-marking as they go, as well as the locomotor and scent-marking behavior of the estrous female. Although not technically aggressive behaviors, they are clearly related to aggressive behavior (Lehman and Adams, 1977) and, therefore, as mentioned above, they been classified along with offense and defense as "agonistic behaviors."

As mentioned above, offense and defense behaviors have also be distinguished in cats (Leyhausen, 1956) and primates (Adams, 1981), although there is some systematic transformation of their motivating stimuli (increased importance of visual stimuli) and motor patterning mechanisms (increased use of the paws and hands, respectively). Patrol/marking, on the other hand, is reduced in advanced primates, and partially overshadowed by another motivational system that I have called the "display motivational system." As there is very little information about the brain mechanisms of display, it will not be treated in this review.

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