The Aggression Systems
Brain Mechanisms of Aggression - Introduction Page 17

Table of Contents


Preface Pages 1 - 2


Human aggression - introduction Pages 3 - 4 - 5 - 6 - 7 - 8


Evolution of aggression - introduction Pages  9 - 10 - 11 - 12 - 13 - 14


Brain mechanisms of aggression - introduction Pages 15 - 16 - 17 - 18 - 19 - 20


Dynamics of aggression - introduction Pages 21 - 22 - 23


As a test case, as reprinted here, we have worked out the brain organization of the releasing stimuli for the upright posture, a motor pattern that is activated by both offense and defense In brief, there are two types of releasing stimuli: an unconditional (inborn) pathway for vibrissal and facial tactile releasing stimuli; and a conditional (learned) pathway for visual stimuli (see diagram on page 10). The unconditional pathway for vibrissal and facial tactile stimuli is organized at the brain-stem level in the trigeminal complex and does not require forebrain participation.

The conditional pathway for visual releasing stimuli requires thalamic and cortical participation, including not only the visual cortex, but also the ventrobasal complex of the thalamus. The participation of this latter structure is especially remarkable because its normal function is for the processing of vibrissal and tactile stimuli. In other words, in the process of conditioning (i.e. learning) the brain is capable of transforming a system used for one modality (in this case, tactile stimulation) into part of a system used for another modality (in this case, vision). If it were not for ethical issues, this could be a very fruitful model for the study of the neural basis of learning. Unfortunately, however, we have concluded that shock-induced boxing is difficult to justify on moral grounds because of the suffering that it causes the animals.

The motivational systems analysis of aggression. as presented here. is not universally accepted by experts on aggression and brain research. Therefore. despite its length. it seems appropriate to reprint here the entire 1979 review and discussion on Brain Mechanisms of Offense, Defense, and Submission as well as the 2006 update in this section. As the recent review indicates, in the decades since the earlier review and debate were published, there have been remarkably few studies published about the predictions that were made, and they tend to confirm the theory of motivational systems.

Because of the complexity of brain anatomy, especially when one tries to review all of the relevant literature about aggression, the figures in the 1979 review are difficult to follow, but the figure in the 2006 review is simpler, as shown on the next page. Also, I am presenting on the following two pages a pair of simplified figures in which the various neural structures involved in offense and defense are projected onto a sagittal view of the rat brain. No attempt is made to illustrate the pathways of releasing and directing stimuli or motor patterning mechanisms.

(Continued on next page)

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