FENS Forum of European Neuroscience edition:7 location:Amsterdam date:3-7 July 2010
During the process of visual-spatial learning visual stimuli become associated with a certain motor act, finally giving rise to goal-directed, complex behavior. In order to elucidate the contribution of the anterior cingulate cortex (aCC), as part of the prefrontal cortex, and the different striatal subregions, namely the dorsomedial (DMS), the dorsolateral (DLS) and the ventral (VS) part, to this type of learning, adult mice were trained in the Morris water maze (MWM), a well established visually-guided spatial navigation task. Performance of mice in the MWM has been previously illustrated to proceed from an early learning phase, characterized by rapid and large performance gains, towards a late learning phase in which further improvements are small and the task becomes increasingly automated. We incorporated both time frames in our experimental setup by training mice for either 2/3 days and 30 days, reflecting respectively the early and late learning phase.
Neural activity levels of the aCC, DMS, DLS and VS in these mice were molecularly visualized by in situ hybridization for the immediate early gene activity markers arc, homer1a and zif268. The optical density was quantified by means of ImageJ and statistical analyses were performed using One Way ANOVA in combination with Fisher's LSD post hoc test.
We demonstrate that the DMS is highly involved in the early MWM learning phase compared to mice trained for 30 days, while simultaneously an opposite shift in activity is observed for the DLS. The VS also shows a higher activity level in overtrained animals upon mice trained for 2 and 3 days. Interestingly, the aCC follows the same pattern of activity over time as the DMS. We propose that these specific changes of activity in the striatal subregions and the aCC amongst others mediate such visual-spatial learning resulting in the shift from initially a cognitive-spatial task to the point where a seemingly effortless execution of the skill is reached.