Converging structural and functional connectivity of orbitofrontal, dorsolateral prefrontal, and posterior parietal cortex in the human striatum

Modification of spatial attention via reinforcement learning (Lee & Shomstein, 2013) requires the integration of reward, attention, and executive processes. Corticostriatal pathways are an ideal neural substrate for this integration because these projections exhibit a globally parallel (Alexander, De Long, and Strick, 1985), but locally overlapping (Haber, 2003), topographical organization. Here, we explored whether there are unique striatal regions that exhibit convergent anatomical connections from orbitofrontal cortex (OFC), dorsolateral prefrontal cortex (DLPFC), and posterior parietal cortex. Deterministic fiber tractography on diffusion spectrum imaging data from neurologically healthy adults (N=60) was used to map fronto-and parieto-striatal projections. In general, projections from cortex were organized in a rostral-caudal gradient along the striatal nuclei; however, we also identified two bilateral convergence zones--one in the caudate nucleus and another in the putamen--that consisted of voxels with projections from OFC, DLPFC, and parietal regions. The distributed cortical connectivity of these striatal convergence zones was confirmed with follow-up functional connectivity analysis from resting state fMRI data from 55 of the participants, in which a high percentage (62-80%) of structurally connected voxels also showed significant functional connectivity. These results delineate a neurologically plausible network of converging corticostriatal projections that may support the integration of reward, executive control, and spatial attention that occurs during spatial reinforcement learning.