Increased dopamine release after working-memory updating training: Neurochemical correlates of transfer

Previous work demonstrates that working-memory (WM) updating training results in improvedperformance on a letter-memory criterion task, transfers to an untrained n-back task, and increasesstriatal dopamine (DA) activity during the criterion task. Here, we sought to replicate and extend thesefindings by also examining neurochemical correlates of transfer. Four positron emission tomography(PET) scans using the radioligand raclopride were performed. Two of these assessed DAD2 binding(letter memory; n-back) before 5 weeks of updating training, and the same two scans were performedpost training. Key findings were (a) pronounced training-related behavioral gains in the lettermemorycriterion task, (b) altered striatal DAD2 binding potential after training during letter-memoryperformance, suggesting training-induced increases in DA release, and (c) increased striatal DA activityalso during the n-back transfer task after the intervention, but no concomitant behavioral transfer.The fact that the training-related DA alterations during the transfer task were not accompanied bybehavioral transfer suggests that increased DA release may be a necessary, but not sufficient, conditionfor behavioral transfer to occur.