Frontal and temporal dopamine release during working memory and attention tasks in healthy humans:: a positron emission tomography study using the high-affinity dopamine D2 receptor ligand [11C]FLB 457

Experimental studies on animals have shown that dopamine is a key neurotransmitter in the regulation of working memory (WM) functions in the prefrontal cortex. In humans, blood flow studies show prefrontal involvement in WM functions, but direct evidence for the involvement of the dopaminergic system in WM is lacking. Using positron emission tomography with a recently developed high-affinity dopamine D-2 receptor tracer, [C-11] FLB 457, we explored frontal, temporal, and parietal D-2 receptor availability in 12 healthy volunteers while they were performing verbal WM and sustained attention tasks. During the performance of both tasks, reduced D-2 receptor availability was observed in the left ventral anterior cingulate, suggesting an attention or arousal-related increase in dopamine release during these tasks. Compared with the sustained attention task, the verbal WM task reduced D-2 receptor availability in the ventrolateral frontal cortex bilaterally and in the left medial temporal structures (amygdala, hippocampus), suggesting that dopamine release in these regions might have a specific role in WM. In addition, correlation analyses indicated that increased dopamine release in the right ventrolateral frontal cortex and the left ventral anterior cingulate during the WM task was associated with faster and more stable WM performance, respectively. Our results indicate that regionally specific components of the frontotemporal dopaminergic network are functionally involved in WM performance in humans.