Spatial learning and performance in the radial arm maze is impaired after N-methyl-D-aspartate (NMDA) receptor blockade in striatal subregions

These experiments addressed the role of striatal N-methyl-D-aspartate (NMDA ) receptors in spatial behavior in the radial arm maze. Rats treated with t he NMDA antagonist D-2-amino-5-phosphonopentanoic acid (AP-5) in the nucleu s accumbens core, medial caudate, and posterior caudate were all significan tly impaired in acquiring the correct spatial responses. In contrast, rats infused with AP-5 in the nucleus accumbens shell showed little impairment. When rats in all groups had learned the maze and were performing at similar levels, AP-5 had relatively little effect except in the posterior caudate group, where errors and trial times were again increased. These findings de monstrate the importance of NMDA receptor-dependent activity within the acc umbens and caudate :in spatial learning and performance. The neural process es necessary for adaptive spatial learning in complex environments may recr uit multiple cortical systems having specialized functions, which in turn a re integrated in widespread striatal regions.