Table 1.
Coordinates for center-of-mass of clusters from each of the k-means parcellations.
Fig 1.
A) Variation of information metric for each K value and each hemisphere. Error bars represent 95% confidence intervals. B) Hierarchy index for each K value and each hemisphere. C) Symmetry measurement between the left and right hemispheres for each K value. D) Average of the standard deviation in the center-of-gravity across clusters for each K value.
Fig 2.
Cluster maps for all clustering solutions for the regions of cytoarchitectonic regions identified by Bludau et al. (2013) as frontal pole.
Colors used here correspond to the colors of the labels and/or tracts in the following figures.
Fig 3.
Tracts originating from each of the clusters in the left hemisphere K = 6.
Label colors (on left) match the cluster colors in Fig 2 (K = 6), which is reproduced at the bottom right. The color scale on brain maps represents the proportion of tract overlap across the participants, with the maps thresholded at 50%. Axial slices are shown in the left column, with slice locations marked on the sagittal slice with a blue line. Sagittal slices are shown in the right column, with slice locations marked on the axial slice with a blue line. MNI coordinates for the z-axis (axial slices) and x-axis (sagittal slices) are shown above the top row.
Fig 4.
Tracts originating from each of the clusters in the right hemisphere K = 4. Label colors (on left) match the cluster colors in Fig 2 (K = 4), which is reproduced at the bottom right.
The color scale on brain maps represents the proportion of tract overlap across the participants, with the maps thresholded at 50%. Axial slices are shown in the left column, with slice locations marked on the sagittal slice with a blue line. Sagittal slices are shown in the right column, with slice locations marked on the axial slice with a blue line. MNI coordinates for the z-axis (axial slices) and x-axis (sagittal slices) are shown above the top row.
Fig 5.
Figure showing the number of clusters that are connected to fiber tracts for the left K = 6 solution (top) and the right K = 4 solution (bottom).
Color bars are shown on the left, with darker red indicating lower overlap and brighter red indicating greater overlap. Most cluster tracts had some degree of overlap with other cluster tracts.
Fig 6.
Tracts that had significantly greater connectivity strength to a designated cluster compared to the average of all other cluster tracts for the left hemisphere K = 6 solution.
Comparisons were cluster-level FWE-corrected to p<.01. The color of the tract and the label corresponds to the color of the cluster in Fig 2. Axial slices are shown in the left column, with slice locations marked on the sagittal slice with a blue line. Sagittal slices are shown in the right column, with slice locations marked on the axial slice with a blue line. MNI coordinates for the z-axis (axial slices) and x-axis (sagittal slices) are shown above the top row.
Fig 7.
Tracts that had significantly greater connectivity strength to a designated cluster compared to the average of all other cluster tracts for the right hemisphere K = 7 solution.
Comparisons were cluster-level FWE-corrected to p<.01. The color of the tract and the label corresponds to the color of the cluster in Fig 2. Axial slices are shown in the left column, with slice locations marked on the sagittal slice with a blue line. Sagittal slices are shown in the right column, with slice locations marked on the axial slice with a blue line. MNI coordinates for the z-axis (axial slices) and x-axis (sagittal slices) are shown above the top row.
Fig 8.
Cluster maps for all clustering solutions for the frontal pole as defined by the Bludau cytoarchitectonic atlas with data from 30 participants from the Human Connectome Project.
The Average Cluster Maps were created by dilating the surface maps for each subject with a 2mm spherical kernel, and averaging the resulting maps. The averaged maps shown here were thresholded to only show voxels where the cluster was present in at least 50% of the participants. Colors in the average cluster maps correspond to the closest cluster in Fig 2. The Individual Cluster Maps show the undilated cluster maps from one representative participant (as noted in the text, the undilated surfaces are difficult to average together). The images are from an off-center anterior view in order to show the medial surfaces. Colors in the individual maps do not correspond to the average cluster maps due to graphics software limitations.
Fig 9.
Tracts originating from each of the cluster in the left K = 6 solution (top) and the right K = 4 solution (bottom) for the Human Connectome Project data.
Tract colors match the cluster colors in Fig 8 (average cluster maps). Tracts connecting to these clusters were present in at least 33% of the participants.
Fig 10.
Meta-analytic functional co-activation maps for each cluster of the left K = 6 solution.
The colors match the cluster labels in Fig 2 (K = 6), reproduced on the right. The degree of overlap in the co-activation maps in shown in the bottom row, with the color scale for the overlap shown at the bottom of the figure.
Fig 11.
Meta-analytic functional co-activation maps for each cluster of the right K = 4 solution.
The colors match the cluster labels in Fig 2 (K = 4), reproduced on the right. The degree of overlap in the co-activation maps in shown in the bottom row, with the color scale for the overlap shown at the bottom of the figure.
Fig 12.
Proposed organizational framework for the frontal pole.
We propose that the frontal pole has both a medial-lateral gradient of function as well as a ventral-dorsal gradient of function. Medial areas of FP integrate information from regions involved in monitoring behavior and regulating emotion. Lateral areas (particularly dorsal lateral) connect to posterior PFC regions and to parietal cortex. As such, dorsal lateral areas are involved in maintaining cognitive representations and action plans. Ventral FP connected to regions thought to be involved in linking stimuli to values and emotions.