Morphological patterns and spatial probability maps of the superior parietal sulcus in the human brain

Abstract

The superior parietal sulcus (SPS) is the defining sulcus within the superior parietal lobule (SPL). The morphological variability of the SPS was examined in individual magnetic resonance imaging (MRI) scans of the human brain that were registered to the Montreal Neurological Institute (MNI) standard stereotaxic space. Two primary morphological patterns were consistently identified across hemispheres: (i) the SPS was identified as a single sulcus, separating the anterior from the posterior part of the SPL and (ii) the SPS was found as a complex of multiple sulcal segments. These morphological patterns were subdivided based on whether the SPS or SPS complex remained distinct or merged with surrounding parietal sulci. The morphological variability and spatial extent of the SPS were quantified using volumetric and surface spatial probabilistic mapping. The current investigation established consistent morphological patterns in a common anatomical space, the MNI stereotaxic space, to facilitate structural and functional analyses within the SPL.

Keywords: MNI space; MRI; probability maps; sulcal morphology; superior parietal sulcus.

Fig. 1

Sulcal map of the lateral surface of the human brain a) by Petrides (2012, , and cytoarchitectonic map b) by Economo and Koskinas (1925). For the sulcal map of Petrides, please see Petrides (2019) for abbreviations not found in the text. Figure 1a reproduced with permission by Elsevier. Note the location of areas PEm and PEp anterior and posterior to the SPS in the Economo and Koskinas (1925) map. Abbreviations: IPL, inferior parietal lobule; IPS, intraparietal sulcus.

Fig. 2

Sulcal map of the medial surface of the human brain a) by Petrides (2012, , and cytoarchitectonic map b) by Economo and Koskinas (1925). Figure 2a reproduced with permission by Elsevier. Note the location of areas PEm and PEp anterior and posterior to the SPS in the Economo and Koskinas (1925) map. Abbreviations: mcgs, marginal ramus of the cingulate sulcus; PrCu, precuneus; prcus, precuneal sulcus.

Fig. 3

Schematic drawing illustrating the 2 main morphological patterns of the SPS, drawn in orange, in relation to its neighboring parietal sulci. a) Subtype Ia: The SPS is a single, distinct sulcus that does not blend with any neighboring sulci; b) Sutype Ib: The SPS is a single sulcus that merges with the SPCS; c) Subtype Ic: The SPS is a single sulcus that merges with the IPSa; d) Subtype Id: The SPS is a single sulcus that merges with the IPSp; e) Subtype Ie: The SPS is a single sulcus and extends over the midline and merges with a precuneal sulcus (prcus) on the medial surface of the brain; f) Subtype IIa: The SPS is found in 2 or more separate branches that do not merge with any neighboring parietal sulci; g) Subtype IIb–e: The SPS is found in 2 or more separate branches and at least one branch merges with a neighboring parietal sulcus. Abbreviations: IPSC, inferior postcentral sulcus; pof, parieto-occipital fissure.

Fig. 4

Volumetric probability maps of the Type I SPS from left and right hemispheres superimposed onto coronal and horizontal sections of the MNI152 2009c asymmetric template that was used for registration. For the coronal sections, the y-coordinate is indicated in the upper right corner of each section; the x- and z-coordinates are shown on the appropriate axes. For the horizontal sections, the z-coordinate is indicated in the upper right corner of each section; the x- and y-coordinates are shown on the appropriate axes. The color bar indicates the extent of overlap of the labeled voxels.

Fig. 5

Volumetric probability maps of the Type II SPS from left and right hemispheres superimposed onto coronal and horizontal sections of the MNI152 2009c asymmetric template that was used for registration. For the coronal sections, the y-coordinate is indicated in the upper right corner of each section; the x- and z-coordinates are shown on the appropriate axes. For the horizontal sections, the z-coordinate is indicated in the upper right corner of each section; the x- and y-coordinates are shown on the appropriate axes. The color bar indicates the extent of the overlap.

Fig. 6

Surface probability maps of the SPS from a) Type I left hemispheres, b) Type I right hemispheres, c) Type II left hemispheres, d) Type II right hemispheres. All probability maps have been overlaid onto the surface template, fsaverage, used for registration. The color bar indicates the extent of overlap of the labeled vertices. The x-, y-, z-coordinates below each surface indicate the position, in MNI305 stereotaxic space, of the vertex with the maximum overlap. Abbreviations: A, anterior; D, dorsal; CS, central sulcus; PCS, postcentral sulcus.