A double dissociation between the rat hippocampus and medial caudoputamen in processing two forms of knowledge

Rats with hippocampus, medial caudoputamen (CPU), lateral CPU, or control l esions were trained on declarative and procedural knowledge variants of a n ovel rodent sequential learning task. Medial CPU lesions impaired rats' abi lity to learn the procedure of running through a sequence of open maze arms but did not disrupt their capacity to explicitly generate (i.e., "declare" ) maze arm sequences. Hippocampus lesions produced the opposite set of resu lts. Rats with lateral CPU lesions were not impaired on either version of t he task. Transfer tests indicated that control rats predominantly used egoc entric cues to solve the procedural task and allocentric spatial cues to so lve the declarative task. These findings suggest a double dissociation betw een the medial CPU and hippocampus in processing egocentric-procedural and allocentric-declarative sequential information, respectively.