Parcellation in left lateral parietal cortex is similar in adults and children

Abstract

A key question in developmental neuroscience involves understanding how and when the cerebral cortex is partitioned into distinct functional areas. The present study used functional connectivity MRI mapping and graph theory to identify putative cortical areas and generate a parcellation scheme of left lateral parietal cortex (LLPC) in 7 to 10-year-old children and adults. Results indicated that a majority of putative LLPC areas could be matched across groups (mean distance between matched areas across age: 3.15 mm). Furthermore, the boundaries of children's putative LLPC areas respected the boundaries generated from the adults' parcellation scheme for a majority of children's areas (13/15). Consistent with prior research, matched LLPC areas showed age-related differences in functional connectivity strength with other brain regions. These results suggest that LLPC cortical parcellation and functional connectivity mature along different developmental trajectories, with adult-like boundaries between LLPC areas established in school-age children prior to adult-like functional connectivity.

Figure 1.

(A) A 27 × 27 grid of 6 mm ROIs was placed over parietal, occipital, and temporal cortex to yield full coverage of LLPC. (B) Similar LLPC boundary maps were seen in adults (upper) and children (lower). (C) A comparable number of putative LLPC areas was detected in adults (13 in LLPC, 21 total in patch) and children (15 in LLPC, 25 total in patch). White spheres denote the location of putative areas anywhere in the patch, both inside and outside LLPC. (D) A magnified view reveals the overlap in putative LLPC area locations for adults (blue boxes) and children (red spheres). (E) A majority of LLPC areas matched across adults (boxes) and children (spheres). Matched putative LLPC areas shown in colors and unmatched areas shown in white. Different colors are used to demonstrate pairs of child and adult areas that were considered a “match.”

Figure 2.

Functional connectivity maps for the matched putative area in angular gyrus (A) and posterior inferior parietal lobule (pIPL) (B) in adults (left column), children (middle column), and the direct comparison of those data (right column). (C) Different functional relationships between putative LLPC areas and frontal and parietal brain regions drove statistically significant group differences.

Figure 3.

Construction of parietal–cortical neighbor networks for adults (upper row) and children (lower row). For each putative LLPC area (4 examples shown for adults [upper row] and children [lower row], the strongest points of functional connectivity with the putative area were identified (these points were termed neighbors) and combined to generate a parietal–cortical neighbor network (right panel).

Figure 4.

Community detection results from adults (upper row) and children (lower row); node color indicates community assignment. The colors for community assignment are arbitrarily generated for each group. (A) Parietal–cortical neighbor networks depicted using spring embedding (SoNIA, http://www.stanford.edu/group/sonia). The presence and strength of rs-fcMRI correlations determines node placement. (B) Lateral and medial and (C) rotated left lateral views of community assignments using Caret software. (D). Lines drawn based on adult LLPC community divisions to generate a systems-level parcellation scheme and applied to children reveal similar LLPC parcellation schemes across age groups.