Figure 1.
Functional connectivity-based parcellation of the caudate (A) and putamen (B) for cluster solutions with different K.
Part A: Coronal view showing the caudate clusters identified by K = 2, 3, and 9 and the putamen clusters identified by K = 2, 3, and 6. Part B: Axial view for these same results. With an increase in K, the functional subdivisions of the caudate and putamen were much more detailed and segmented along the ventro-dorsal, anterior-posterior, or medio-lateral axis. All parcellation results (i.e., K = 2–10) are presented in Figure S1 and S2.
Figure 2.
Stability of cluster solutions for the caudate and putamen and functional parcellation of the entire striatum mask.
Part A: VI scores for the caudate and putamen, respectively, based on a split-half comparison procedure with permuted groups. The graph plots the mean VI across 100 permutations for each K cluster solution. The asterisks indicate the number of subdivisions that can be stably estimated by the clustering algorithm, in which VI is statistically indistinguishable from that of the K–1 solution. There were no VI differences between K = 8 and 9 (t = −1.76, p = 0.08) for the caudate, and no differences between K = 5 and 6 (t = 0.027, p = 0.98), K = 6 and 7 (t = 1.04, p = 0.30), K = 7 and 8 (t = 0.714, p = 0.48), and K = 8 and 9 (t = −0.16, p = 0.87) for the putamen. Part B: Clustering result of the entire striatum mask including the caudate and putamen in the K = 2 cluster solution. The pattern of functional subdivision (right panel) in the entire striatum is very similar to its anatomical subdivision (left panel).
Figure 3.
Functional connectivity maps of the entire caudate and its subdivisions in the K = 2, 3, and 9 cluster solutions.
Red and blue indicate areas showing positive functional correlation and negative functional correlation with seed region, respectively. The ventral and dorsal caudate clusters were positively connected to areas involved in emotional processes and cognitive processes, respectively.
Figure 4.
Functional connectivity maps of the entire putamen and its subdivisions in the K = 2, 3, and 6 cluster solutions.
Red and blue indicate positive and negative functional correlation with the seed region, respectively. The rostral putamen clusters were positively connected to areas involved in emotional and cognitive processes, while the caudal putamen clusters were positively connected to motor areas.
Figure 5.
ROI analysis results for functional connectivity between striatal clusters identified using clustering algorithms (K = 3) and other brain regions, segmented based on the AAL atlas.
The x-axis indicates brain regions, and the y-axis indicates the strength of functional connectivity between each cluster as a seed region and other brain regions, as correlation z scores. The red and blue bars respectively indicate the area located in the right and left hemisphere. The red, blue, and purple asterisks respectively indicate that these regions located on the right, left, or bilaterally had significant functional connectivity with the cluster region under a false discovery rate threshold of q<0.05. All ROI-to-ROI results for striatal clusters identified by different K are presented in Figure S3–S5.
Figure 6.
ROI analysis results for functional connectivity between striatal and thalamic clusters and other regions that belong to CSTC loops.
Part A: Clustering results of the caudate, putamen, and thalamus based on functional connectivity patterns across regions belonging to CSTC loops. Part B: Correlations of the caudate clusters with other regions. Part C: Correlations of the putamen clusters with other regions. The x-axis indicates the strength of functional connectivity between the clusters and other brain regions as correlation z scores, and the y-axis indicates brain regions. For simplicity, we focused on results from bilateral ROI regions. The black asterisks indicate regions with significant functional connectivity with the cluster regions under a false discovery rate threshold of q<0.05.
Figure 7.
Summary of striatal subdivisions and their functional connectivity maps.
The schematic illustrates parcellations based on the optimal K (9 and 6 for the caudate and the putamen respectively). Regions showing significant functional connectivity to each striatal cluster are depicted on the surface and the section of the brain, and are also listed. IOC, inferior occipital cortex; med-PFC, medial prefrontal cortex; ACC, anterior cingulate cortex; MCC, middle cingulate cortex; DLPFC, dorsolateral prefrontal cortex; CALC, calcarine cortex; ITC, inferior temporal cortex; INS, insula; STC, superior temporal cortex; lat-PFC, lateral prefrontal cortex; MTC, middle temporal cortex; IPC, inferior parietal cortex; AMY, amygdala; Caud, caudate; THAL, thalamus; OFC, orbitofrontal cortex; PCC, posterior cingulate cortex; HIPP, hippocampus; SMA, supplementary motor area; SPC, superior parietal cortex; PreC, precentral cortex.