Critically, there was a cluster in left caudate in which there was a training-induced decrease of raclopride binding to D2 receptors (Fig. 6C). Fig. 6D illustrates changes in ligand binding to striatal D2 receptors for the letter memory minus control task contrast pre and post training in the peak of this cluster. Note that the negative binding values (Gz) reflect generally lower binding for letter memory than for the control task. The most striking feature of Fig. 6D is the marked decrease in binding for the letter-memory task following training, indicating increased DA release during WM performance. Interestingly, the left caudate locus of the training-induced striatal effect overlapped with the area in which Dahlin et al. (2008b) observed increased BOLD activity post training. Thus, these findings indicate that training of updating is associated with increased release of striatal DA.