Effect of medial thalamic lesions in responses elicited by tooth pulp stimulation

Abstract

Cats were placed in a shuttle box and trained to escape an electrical stimulus delivered to the tooth pulp. Subsequently, bilateral electrolytic lesions were produced in the medial thalamus. Four to fourteen days postoperatively, the animals were again placed in the experimental apparatus every third day and received 10 trials per session. This procedure was continued for a period of 3 months. The animals were then killed and the histological observations were correlated with the behavioral data. It was observed that lesions destroying at least 50% of the centrum medianum-parafascicularis complex bilaterally were effective in completely abolishing the escape response elicited by tooth pulp stimulation. However, if significant portions of the anterior and/or lateral part of centrum medianum were not destroyed the reaction was not completely abolished although the latency for the response was prolonged. In such cases it was necessary to eliminate variable amounts of the nucleus subparafascicularis (and perhaps also commissuralis interventralis) in order to completely a-bolish the response.