Society for Neuroscience edition:39 location:Chicago date:17-21 October 2009
Visuo-spatial learning, a dynamic process in which visual stimuli guide a motor response, leads to goal-directed, complex behavior. In order to understand how and when the striatum and the hippocampus contribute to this type of learning, we trained adult mice in the Morris water maze (MWM), a robust visually-guided spatial navigation test. Performance of mice in the MWM has been illustrated to proceed from an early learning phase, characterized by rapid and large performance gains, towards a late learning overtrained phase in which further improvements are small and the task becomes increasingly automated. We propose that specific changes in the activation patterns within the striatum and the hippocampus mediate such visuo-spatial learning resulting in the improvement and the eventual seemingly effortless execution of the visuo-spatial skill.
Neural activity patterns within the striatum and the hippocampus were molecularly characterized by in situ hybridization for the immediate early gene activity markers arc (activity-regulated cytoskeleton-associated protein), homer1a and zif268 (zink finger protein 268). Two timeframes mirroring the early learning (2 and 3 days of MWM training) and the late learning (30 days of MWM training) phase were compared by optical density measurements of the hybridization signal using Zeiss AxioVision Rel.4.6 software. Each of the three immediate early genes displayed a distinct subregional expression pattern in relationship to the two phases in the learning curve in both hippocampus and striatum. Combined with human fMRI data on virtual water maze learning, this will allow cross-species comparison of (sub)region-specific adaptations to circuits involved in visuo-spatial learning.