Spatial probability maps of the segments of the postcentral sulcus in the human brain

Abstract

The postcentral sulcus is the posterior boundary of the postcentral gyrus where the somatosensory cortex is represented. In the human brain, the postcentral sulcus is composed of five distinct segments that are related to the somatosensory representation of different parts of the body. Segment 1 of the postcentral sulcus, located near the dorsomedial boundary of each hemisphere, is associated with toe/leg representations, segment 2 with arm/hand representations, segment 3 with blinking, and segments 4 and 5, which are near the lateral fissure and the parietal operculum, with the mouth and tongue representations. The variability in location and spatial extent of these five segments were quantified in 40 magnetic resonance imaging (MRI) anatomical brain scans registered to the stereotaxic space of the Montreal Neurological Institute (MNI space), in the form of volumetric (using MINC Toolkit) and surface (using FreeSurfer) spatial probability maps. These probability maps can be used by researchers and clinicians to improve the localization of the segments of the postcentral sulcus in MRI images of interest and also to improve the interpretation of the location of activation peaks generated in functional neuroimaging studies investigating somatosensory cortex.

The superior frontal sulcus in the human brain: Morphology and probability maps

“…Previous qualitative analyses of the SFS have consistently described the morphological variations of this sulcus (see Section 4.1), particularly in comparison to the classic sulcal maps (see Figure 2; Eberstaller, 1890; Cunningham, 1905; Bailey & Bonin, 1951; Connolly, 1950; Ono et al, 1990; Juch et al, 2005; Ribas et al, 2006; Gonul et al, 2014). This inter‐individual morphological variability is significant given that it is maintained despite linear registration of brains to the axes of MNI standard stereotaxic space for morphological analyses (Drudik et al, 2023; Sprung‐Much & Petrides, 2018, 2020; Zlatkina et al, 2022). Inspection of the volumetric probability maps reveals that the anterior and posterior ends of the SFS occur at around the same z‐coordinates in both hemispheres, and overlap closely with the depiction of the SFS in the average brain represented in MNI standard stereotaxic space that was used for registration (see Figures 3–5).…”

“…This fact can, in part, explain the inconsistency across results from functional neuroimaging studies, which usually represent data as a group coordinate projected onto the average cortical surface and cannot resolve distinct cortical regions that are close to each other in space, but differ in functional processing (Amiez et al, 2006 ). Taken together, this reasoning implies that in order to establish accurate structure‐to‐function relationships, functional activation peaks should be presented in relation to individual subject sulcal and gyral morphology to account for all the features of a sulcus that may act as a functional landmark (Amiez et al, 2006 , 2008 ; Amiez & Petrides, 2018 ; Juch et al, 2005 ; Luna et al, 1998 ; Rubenstein & Rakic, 1999 ; Tomaiuolo & Giordano, 2016 ; Zlatkina et al, 2016 , 2022 ).…”

“…The general relation between structure and function can be obtained by relating functional activation peaks to sulcal landmarks (Amiez et al, 2006 ; Amiez & Petrides, 2018 ; Germann & Petrides, 2020a , 2020b ; Huntgeburth et al, 2017 ; Segal & Petrides, 2013 ; Zlatkina et al, 2022 ). In Figure 7 , we illustrate the location of functional activity peaks in individual subjects reported by Amiez and Petrides ( 2018 ) in a functional magnetic resonance imaging (fMRI) study that examined basic saccadic eye or hand actions, as well as cognitive selection between competing hand or eye movements based on previously learned conditional relations (i.e., if instruction stimulus A is presented, select movement X; but if instruction stimulus B is presented, select movement Y).…”

“…However, upon closer inspection within the depth of the cortex, these sulci were separated from the SFS by way of a submerged gyral passage ( pli de passage ). These variations were considered to be clearly distinct from the SFS by detecting a pli de passage in at least one horizontal section (i.e., at least 1 mm in size), in tandem with reconstructed cortical surfaces (Zlatkina et al, 2022 ).…”

“…These variations were considered to be clearly distinct from the SFS by detecting a pli de passage in at least one horizontal section (i.e., at least 1 mm in size), in tandem with reconstructed cortical surfaces (Zlatkina et al, 2022).…”