Does pretraining spare the spatial deficit associated with anterior thalamic damage in rats?

Rats that had been pretrained on 2 tests of allocentric memory (water maze and T maze) received bilateral cytotoxic lesions in the anterior thalamic n uclei (ATN) or transection of the fimbria-fomix (FF). After surgery, both g roups of rats were impaired on both tasks, although the preoperative traini ng resulted in a rapid initial reacquisition of the water maze task. Those rats with lesions largely restricted to the ATN were impaired at a level co mparable to that produced by FF lesions. This finding is consistent with a close functional relationship between the hippocampus and the ATN, necessar y for the acquisition and on-line processing of allocentric spatial informa tion but not for the maintenance/retrieval of procedural information. The r ats with more extensive thalamic lesions were more impaired in both tasks a nd did show a loss of procedural information.