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When compared by a simple statistical test, the Fisher's Exact Test for a 2 x 2 contingency table , the bilateral complete ventrobasal complex lesion which abolished boxing in seven of eight rats, was significantly more effective than all other lesions combined, which abolished boxing in one of the other nine lesioned rats (p<0.005).
Visually-released boxing was also abolished in two rats with unilateral lesions of the ventrobasal thalamus and closure of the eye ipsilateral to the lesion. In Rat 12 the boxing was abolished following a complete lesion of the left ventrobasal thalamus and closure of the left eye; and in Rat 15 the boxing was abolished following a complete lesion of the right ventrobasal thalamus and closure of the right eye. Low levels of visually-released boxing were shown by each animal on other tests when the ipsilateral eye was open and the contralateral eye was sewn closed. The lesions of Rats 12 and 15 were especially restricted to the ventrobasal thalamus and did not involve consistent and complete destruction of any other structure (see Fig. 1).
Facial anesthesia did not usually change the threshold or probability of the upright posture and boxing in control animals, although it did affect the quality of the response. The mean threshold remained at 0.10 mA and the percentage of shocks with boxing fell only from 24.8% to 19.4% in the five control animals. Following facial anesthesia, the tracking movements by which rats normally follow the movements of the opponent along side-to-side and front-to-back dimensions were abolished. Perhaps as a result of this deficit, the experimental animals with facial anesthesia were often bitten on the nose by their intact opponents, which never occurred in any pairs of normal animals. A similar finding has been reported by Thor and Ghiselli .