Updated Review-16

Learning must be involved in the releasing and directing of approach and escape locomotion (point 2 in the figure). However, despite continued progress on the neural mechanisms by which locomotion is guided (Mulder et al., 2004), a connection has not yet been made between that research and the brain mechanisms of offensive approach and defensive escape. A related question is how the brain chooses among competing motor patterns at a given moment. In the previous review (Adams, 1979a) it was suggested that the cerebellum might be involved in this process of response selection. Although this suggestion has not been supported by further research, a promising research methodology has been presented recently by Mongeau et al (2003); they compared c-Fos activity when a mouse chose freezing to activity when a mouse chose flight in response to an ultrasound stimulus.

Little work has been done on the neural mechanisms of releasing and directing stimuli of aggressive motor patterns since we published data on releasing and directing stimuli for the upright posture motor pattern (Kanki and Adams, 1978). Under normal circumstances, motor patterns do not occur until the appropriate releasing and directly stimuli are present, but this may not always be the case. Jaap Koolhaas and I began some work on this in 1981 in his laboratory, depriving offensive rats of hearing (earplugs), eyesight (testing in darkness) and vibrissal sensation (snout denervation). When tested with an intruder which they could smell but could not find, the animals began to engage in "vacuum" attacks against an imaginary opponent. We did not continue, however, because the tests produced grand mal seizures in some cases which called into question the ethics of the experiment. The effect suggests the possibility that sensory systems may be potentiated by the motivational system to the point that the animal "hallucinates" its opponent. Potentiation of sensory systems during motivated behavior has been demonstrated for the predatory attack of cats (MacDonnell and Flynn, 1966).