Previous studies have demonstrated that plastic changes associated with experience can be observed in the brains of adult humans and mice using MRI. For example, the extensive navigational experience of London taxi drivers is associated with increased hippocampal volume and learning to juggle leads to selective structural changes in the brains of young adults. The goal of this study was to investigate these experience induced structural changes more closely using MRI in mice. To induce differential plastic brain changes mice were trained in different versions of the Barnes maze. In the Barnes maze mice are placed in the centre of a highly lit platform. Along the edge of the platform there are 40 holes, one of which is connected to an escape box that gives mice the chance to escape the exposed situation. In the spatial version of the Barnes maze numerous distal landmarks are placed around the platform and mice learn to use the spatial landmarks to navigate quickly to the escape box. In the non-spatial version of the Barnes maze the escape box is moved to a different hole every trial but a flag is always placed next it. Mice learn to approach the flag to find the escape box. All images were obtained using a high-field MR scanner (7T). To investigate the time course of possible structural brain changes live imaging of anesthetized mice (125µm voxel resolution) was performed before and at various time-points during and after training. Some mice were sacrificed 10 days after training and their brain fixed and high resolution anatomical images (32µm voxel resolution) and Diffusion weighted images (150µm voxel resolution) obtained. Automated registration algorithms were used to localize subtle anatomical differences

We observed changes in specific brain regions. Learning the spatial version of the Barnes maze is associated with changes primarily in the hippocampus. Learning the non-spatial version of the Barnes maze is associated with changes primarily in the striatum. These local change can be observed in the first days of training and persist for remainder of the experiment. Additionally the variation in learning performance between mice is reflected in the amount of local structural change.