Effects of Working-Memory Training on Striatal Dopamine Release

摘要

The ability to update working memory (WM) underlies many higher-order cognitive functions. Neuroimaging (1) and computational (2) evidence links updating to striato-frontal circuits, wilh dopaminergic neurotransmission critically implicated (5). Phasic dopamine (DA) activity is important to transient neural processes such as updating (4). Updating training improves performance and leads to increased caudate blood oxygen level-dependent (BOLD) activity (1). Given that the striatal BOLD signal is influenced by DA activity (5), updating training might alter DA D2 signaling. However, a previous study of DA neurotransmission after WM training (6) showed changes in cortical Dl receptors but failed to demonstrate effects on the striatal D2 system, likely because the training regimen promoted sustained maintenance processes and scanning was performed during rest only. We used activation positron emission tomog- raphy (PET) and the radioligand raclopride to measure binding potential (BP) for striatal D2 receptors before and after 5 weeks of updating training. In a single-scan dynamic PET measurement (7), we assessed transient changes in striatal D2 receptor binding during a letter-memory updating task compared with a control task. According to the displacement principle, changes in DA release are inferred when BP is reduced during a cognitive challenge, because of competition between the radioligand and endogenous DA in binding to receptors (8).