Abstract
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Objectives: Studies conducted on laboratory animals have implicated striatal dopamine in the processing of emotional memory. It has been shown that post-training activation of striatal dopamine receptors improves memory for emotional events in rats. Even though the role of dopamine in human emotional memory processing is unclear, several studies have suggested that striatal dopamine is involved in the expression of human emotions. These studies prompted us to examine whether striatal dopamine is released during processing of emotional memory in healthy volunteers. Methods: We used a molecular imaging technique to study human emotional memory. In this experiment we dynamically measured the concentration of a specific dopamine receptor ligand 11C-raclopride, to examine change in the rate of dopamine released in the striatum during the task performance. After a single intravenous administration of the ligand healthy volunteers were asked to perform an emotional memory task under a control and a test condition. Emotional memories were evoked in the test condition, which was started 25 min after the ligand administration. The ligand concentration was measured using an ECAT HR+ camera. Using this data, the rate of ligand displacement was computed. Results: Behavioral data indicated that emotional memories were evoked in the test condition. Immediately after initiation of this condition, the rate of ligand displacement increased significantly in the head of caudate and in the middle part of the putamen bilaterally. Interestingly, functional neuroanatomical evidence strongly suggests that these striatal areas are associated with emotional memory processing. Conclusions: The results indicate that dopamine is released during processing of emotional memory, and that the molecular imaging technique is a sensitive method for detecting endogenously released striatal dopamine, induced by a change in valence.
Research Support (if any): NIH (1R21MH073624), Dana Foundation, and Shriners Hospital for Children
- Society of Nuclear Medicine, Inc.