Figure 8.

A direct test for a functional gradient within the SN revealed an increased tendency for the ventromedial SN to encode RPEs in the appetitive session, as well as an increased tendency for voxels in the dorsolateral SN to encode an aversive value signal and an RPE signal in the aversive session. A, Anterior view of SN, with voxel location along the ventromedial to dorsolateral axis indicated by heat color palette (binned for illustration purposes only). Location was defined in terms of distance from origin (crosshairs). Subthalamic nucleus (STN) and red nucleus (RN) were added for reference. B, Statistical analyses revealed that fitted parameter estimates show a significant location by condition interaction, confirming the existence of the proposed functional gradient along a ventromedial to dorsolateral axis. Thin lines indicate population mean for each set of equidistant voxels. Shaded areas indicate standard errors. Bold lines indicate predictions of the linear mixed-effects model.