IBOTENIC LESIONS OF THE NUCLEUS-ACCUMBENS PROMOTE REACTIVITY TO SPATIAL NOVELTY IN NONREACTIVE DBA MICE - IMPLICATIONS FOR NEURAL MECHANISMS SUBSERVING SPATIAL INFORMATION ENCODING

The role of the nucleus accumbens (NA) in forming spatial representati ons was investigated in C57BL/6 (C57) and DBA/2 (DBA) inbred mice. One week before testing, bilateral excitotoxic lesions were performed in the NA using ibotenic acid. Testing consisted of placing mice in an ar ena containing 5 objects at a fixed location and, after habituation to the object configuration, examining their reactivity to the displacem ent (spatial novelty) or the substitution (object novelty) of some of these objects. C57 mice reacted to spatial novelty and DBA mice did no t. Both strains, however, reacted to object novelty. The lesion had no effect on C57 mice's performance, but in the DBA mice, it promoted a clear reaction to spatial novelty that was absent in control animals. Radial maze performance also was improved in DBA with NA lesions. Resu lts suggest the NA as a possible site for modulating spatially mediate d behaviors in poor-performing subjects.