Differential learning strategies in spatial and nonspatial versions of the Morris water maze in the C57BL/6J inbred mouse strain

We recently developed a new nonspatial version of the Morris water maze that requires the use of four visually distinct intra-maze patterns to efficiently locate a hidden platform. The nonspatial version was designed to match the spatial version on complexity of cue usage, and differs only on spatiality of cues, thereby allowing more meaningful comparisons between the two versions. Following a previous experiment that demonstrated nonspatial learning with the BXSB inbred mouse strain, C57 inbred mice were tested in this study. They received spatial and nonspatial training in a counter-balanced order so that Test Order and information transfer could be assessed. Subjects that received spatial training first had superior performance in both the spatial and the nonspatial tasks when compared to mice that received nonspatial training first. The mice that received spatial training first used extra-maze cues as a spatial strategy. However, during nonspatial testing they did not use the intra-maze cues to locate the platform; instead, the mice used an egocentric strategy of circling through the platform annulus. Subjects that received spatial testing first were superior on the nonspatial task to those subjects that received nonspatial training first. Moreover, subjects that received nonspatial testing first were unable to learn the spatial version. Overall, C57 mice can learn both the spatial and nonspatial versions of the Morris maze presented here; however, the nonspatial version is more difficult and is solved using an egocentric strategy.