Figure 1. t-maps and time-activity curves showing changes in the rate of ligand dissociation during task performance.

The striatal areas where rate of ligand displacement increased significantly in the Incongruent condition of the flanker task are shown on the t-maps. The most significant increase was observed on the dorsal aspect of the body of left caudate. The time-activity curves show the ligand concentration (open circles) and least square fit (solid lines) in a striatal area (upper curve) and in the reference region (lower curves). The data on the left of the vertical lines were acquired in the Congruent condition and those on the right were obtained in the Incongruent condition. Significant reduction in the ligand concentration in the Incongruent condition suggests that the rate of ligand displacement increased during task performance. The increase was due to competitive displacement induced by endogenously released dopamine. There was no significant change in the rate of ligand displacement in the reference region (cerebellum). The time-activity curves were drawn using the mean data acquired from the voxels where maximum changes were observed in each area. This analysis used the linear extension of reference region tissue model (LE-SRRM).