Lashley maze learning deficits in NZB mice.

In a prior study we found excellent Lashley III maze learning in BXSB mice and poor learning in NZB mice, despite the fact that both strains are autoimmune and develop cortical ectopias. This prompted us to examine NZB Lashley maze performance in detail, including comparisons to other strains and attempts to improve performance by giving additional trials with or without additional intramaze visual cues. In conventional Lashley testing (10 trials), RF mice (non-autoimmune and nonectopic) and BXSBs performed well in the Lashley maze. They had high learning indices and few errors. NZB mice performed poorly, with low learning indices and many errors. Even with additional trials or additional trials plus intramaze cues, NZB performance remained poor. The number of backward and forward errors stayed high; learning indices were low. Since both BXSB and NZB mice develop autoimmune disorders and cortical ectopias, it is unlikely that differential Lashley performance is the result of the presence of these phenomena. NZB mice are known to have alterations in their hippocampal morphology, and this is a possible mediator of the Lashley deficit.