Deficits in mouse-killing following trigeminal lesions in the rat

Abstract

Lesions of the trigeminal somatosensory system were produced in adult male hooded rats that would spontaneously kill C57B1/6 mice (i.e., natural killers). The mouse-killing behavior was assessed by the speed of the initial attack (1/latency in seconds), reflecting the release of the behavior, and the speed and efficiency (1/number of attacks to kill) of killing. Ten-minute test sessions were given once every 2–4 days, 3–4 times prior to trigeminal or control surgery and again 5–6 times following surgery. In three experiments, it was found that lesions of the medial ventrobasal thalamic complex (VBm), trigeminal sensory root, or infraorbital branch of the trigeminal nerve decreased the speed and efficiency of killing. In rats that were induced to kill by food deprivation and were tested while food-deprived, the trigeminal sensory root lesions had the same effects, although the impairment of killing speed was not as marked. Only the VBm lesions decreased the initial attack speeds, and this deficit was attenuated by 2 weeks following surgery. It is concluded that perioral somatosensory cues normally guide the mouse-killing behavior but are not necessary for initiation of attack behavior.