Morphological patterns of the postcentral sulcus in the human brain

Abstract

The morphological structure of the postcentral sulcus and its variability were investigated in 40 structural magnetic resonance images of the human brain registered to the Montreal Neurological Institute (MNI) proportional stereotaxic space. This analysis showed that the postcentral sulcus is not a single sulcus, but rather a complex of sulcal segments separated by gyri which merge its banks at distinct locations. Most of these gyri are submerged deep within the sulcus and can be observed only by examining the depth of the sulcus, although a small proportion may be observed from the surface of the brain. In the majority of the examined cerebral hemispheres (73.75%), the postcentral sulcus is separated into two or three segments, and less frequently into four or five segments (12.5%) or remains continuous (13.75 %). Examination of the in-depth relationship between the postcentral sulcus and the intraparietal sulcus revealed that these two sulci may appear to join on the surface of the brain, but they are in fact always separated by a gyrus in the cortical depth. In 32.5% of the examined hemispheres, a dorso-ventrally oriented sulcus, the transverse postcentral sulcus, is located anterior to the postcentral sulcus on the lower part of the postcentral gyrus. Systematic examination of the morphology of the postcentral sulcus in the proportional stereotaxic space which is used in functional neuroimaging studies is the first step towards the establishment of anatomical-functional correlations in the anterior parietal lobe. 3 IntroductionThe postcentral gyrus, which forms the anterior part of the parietal lobe, is delimited by the central sulcus, anteriorly, and the postcentral sulcus, posteriorly (Figure 1). Pioneer studies using electrical stimulation during brain surgery established that, as in nonhuman primates, the postcentral gyrus of the human brain is the somatosensory cortex and that there is an orderly arrangement of sensory representations of the different parts of the body along its dorsoventral extent (Penfield and Rasmussen, 1952;Woolsey et al., 1979). More recently, the organization of the somatosensory cortex along the postcentral gyrus of the human brain has been examined and confirmed with functional neuroimaging (Nakamura et al., 1998;Boling et al., 1999Boling et al., , 2002Fabri et al., 2005). The postcentral sulcus, which separates the postcentral gyrus from the posterior parietal cortex, is traditionally described as a prominent sulcus extending from the superior aspect of the hemisphere to the lateral fissure (e.g. Ono et al., 1990;Duvernoy et al., 1991). It is sometimes illustrated as a single continuous sulcus (e.g. Smith, 1907;Economo and Koskinas, 1925) or divided into two or three segments which are superior and inferior to each other (e.g. Eberstaller, 1890;Retzius, 1896;Brodmann, 1909;Sarkissov et al., 1955;Ono et al., 1990). The dorsal end of the postcentral sulcus is often depicted as a V-shaped structure consisting of two branches coming together at one point (Brodmann, 1909;Economo and...

Morphological patterns of the intraparietal sulcus and the anterior intermediate parietal sulcus of Jensen in the human brain

“…4 in [21]; [22][23] 8). These coordinates place the activity close to the gyral passage separating the post-central sulcus from the anterior ramus of the IPS [38]. If the narrow gyral passage is visible from the surface of the brain ( figure 2b-d), then the activity appears to be located within the inferior branch of the post-central sulcus, located ventral to the IPS and the anterior ramus of the IPS.…”

“…The methodology is similar to that in the study by Zlatkina & Petrides [38]. The data are based entirely on the examination of continuous series of sections in the region of interest.…”

“…In order to advance understanding of the IPS patterns, it is necessary to examine the depth of the sulci in a continuous series of two-dimensional sections. Such an approach reveals discontinuities by gyral passages located in the sulcal depth, and therefore not visible from surface inspection of the brains [38]. This study examined the morphology of the intraparietal sulcal region in continuous serial two-dimensional sections in order to establish the details of the morphological variations of the IPS and clarify the relationship between its segments, the sulcus of Jensen and the nearby sulci, such as the three caudal branches of the superior temporal sulcus that enter the inferior parietal lobule and approach the IPS.…”

The postcentral sulcal complex and the transverse postcentral sulcus and their relation to sensorimotor functional organization

“…A recent study of the morphology of the postcentral sulcus, which forms the posterior boundary of the central sensorimotor region in the human brain, has shown that it is a complex of distinct sulcal segments (Zlatkina & Petrides, ), raising the question whether these segments relate to the sensorimotor representations of different body parts. It should be noted here that several recent studies have shown that functional activations can often be linked to specific morphological features of the sulci and gyri of the human brain when the functional data are examined in individual subjects, providing better understanding of structure‐to‐function relationships (e.g., Amiez et al ., , ; Amiez & Petrides, , ; Derrfuss et al ., ; Segal & Petrides, ).…”

Sulci as Landmarks

“…Furthermore, the most comprehensive description of the variability of the folding patterns has been provided for a set of only 25 brains (Ono, Kubik, & Abarnathey, 1990), and many configurations have never been described. While an exquisite nomenclature of these secondary and tertiary folds has been recently proposed (Petrides, 2012), comprehensive studies of their variability across individuals are limited to a few areas (Segal & Petrides, 2012;Zlatkina & Petrides, 2010). These pieces can be recombined in nonstandard ways to create unusual folding patterns without clear link with the anatomical nomenclature.…”