The last years have seen an overwhelming amount of research aiming to disentangle the neural mechanisms underlying goal-directed behavior and cognitive control processes. In that regard, the basal ganglia have attracted much interest. It is known that the striatum is a very complex neuroanatomical structure and can be subdivided into the ‘matrix’ and the ‘striosomes’. Yet, it has been unclear whether this striatal microstructure is important to consider for cognitive functions, as well.