Database

Sulci

Structure


Short definition

This part of the database is still under construction.

Definition - HNS

HNS2: Paxinos, G. and Mai, J.K.: The Human Nervous System, 2nd Ed. Academic Press/Elsevier, San Diego, (1366pp.) 2004.
HNS3: Mai, J.K. and Paxinos, G.: The Human Nervous System, 3rd Ed. Academic Press/Elsevier, San Diego, 2011.

A. Lateral Surface of the Frontal Lobe

Precentral region

central sulcus (cs) (Petrides, Pandya, HNS2)
runs in a primarily dorsoventral but more-or-less oblique direction, its dorsal end lying in a more posterior location than its ventral end.  The central sulcus does not usually reach the lateral fissure and is separated from it by a short gyrus, the subcentral gyrus (SCG)

precentral sulci (Petrides, Pandya, HNS2)
The superior (sprs) and inferior (iprs) precentral sulci that lie rostral to the central sulcus and, like the central sulcus, maintain a primarily dorsoventral direction, define the rostral limit of the precentral gyrus (PrG). 

The superior and inferior precentral sulci form the rostral limit of the precentral gyrus and the caudal limit of the superior, middle and inferior frontal gyri (SFG, MFG, IFG in Fig. 1). 
The inferior precentral sulcus, which is the longer one of the two precentral sulci, originates near the lateral fissure and courses dorsally for a considerable distance reaching the posterior margin of the middle frontal gyrus. 
The superior precentral sulcus lies, generally, caudal to the dorsalmost point of the inferior precentral sulcus and is often separated from it by a narrow gyral passage that joins the caudal part of the middle frontal gyrus with the precentral gyrus (see + in Figs. 1 and 2).  In a few cases, this narrow gyral passage may be submerged and, in those cases, the inferior and superior precentral sulci may fuse superficially giving the impression of a single uninterrupted sulcus.  Frequently, there is a more or less horizontally directed extension (he) of the inferior precentral sulcus projecting into the middle frontal gyrus just above the caudal part of the inferior frontal sulcus (see Fig. 1).  This short ramus sometimes merges with one of the adjoining sulci.  In the  brain shown in Figure 2, the horizontal extension (he) veers medially and merges with the inferior frontal sulcus (ifs) and can only be distinguished in coronal and horizontal sections through this region.  
The superior precentral sulcus is shorter than the inferior precentral sulcus and frequently merges with the superior frontal sulcus.  In some brains, a part of the superior or the inferior precentral sulcus may be separated and, in these cases, one may speak of an intermediate precentral sulcus.  However, this is not a useful distinction and the separated part is best considered as belonging to either the superior or the inferior precentral sulcus.   
Dorsal to the superior precentral sulcus, there is often a small dimple that Cunningham labeled the “sulcus precentralis marginalis” (maprs in Figs. 1 and 3).  Rostral to this dimple and often cutting into the medial surface of the hemisphere is the “sulcus precentralis medialis” of Eberstaller.  The medial precentral sulcus (mprs in Figs. 1 and 3) is not really a medially located sulcus but rather a small sulcus located at the midline of the hemisphere that may extend for a variable distance onto the medial surface of the brain. 

frontomarginal sulcus (frontopolar region) Petrides, Pandya (HNS2):

The term “frontomarginal sulcus” was first used by Wernicke (1876) to refer to a deep sulcus that is found at the ventralmost part of the frontal pole (Figs. 1, 2, 4). Eberstaller (1890) and Economo and Koskinas (1925) recognized a complex of three distinct frontomarginal sulci that are running in the ventralmost part of the rostral frontal lobe along the edge with the orbital surface.  These sulci are the medial frontomarginal sulcus (mfms), the intermediate frontomarginal sulcus (ifms), and the lateral frontomarginal sulcus (lfms) (Figs. 1, 2, 4).  The medial and intermediate frontomarginal sulci abut the ventralmost extension of the intermediate frontal sulcus (infs-v).  The lateral frontomarginal sulcus lies rostral and lateral to the horizontal sulcus and is directed dorsally.  In a recent atlas by Duvernoy (1991), the lateral frontomarginal sulcus was labeled as the “lateral orbital sulcus”.  The term “lateral orbital sulcus” has been classically used by several investigators to refer to the lateral part of the H-pattern of the sulcal complex that is lying on the orbital surface of the frontal lobe (e.g. Economo and Koskinas, 1925, pp. 28-31; Bonin and Bailey, 1951, p. 45).  It must be emphasized here that the lateral frontomarginal sulcus lies lateral and dorsal to the lateral orbital sulcus and has been recognized as such by several major investigators such as Eberstaller (1890, p. 84) and Economo and Koskinas (1925, pp. 28-31).

 

B. Orbital Surface of the Frontal Lobe

 

(Petrides, Pandya, HNS2):

At the medialmost part of the orbital surface of the frontal lobe, one can identify the olfactory sulcus (olfs) which is running in a rostro-caudal direction and delimits the gyrus rectus (RG) which lies medial to it (Figs. 1 and 5).  Typically, the posterior end of the olfactory sulcus lies more lateral than its anterior end (Chiavaras and Petrides, 2000).  Lateral to the olfactory sulcus, there are two longitudinally directed sulci, the medial (mos) and lateral (los) orbital sulci which are joined together by the transverse orbital sulcus (tos) to form the impression of an H or a K pattern.  The medial and lateral orbital sulci can be divided into rostral and caudal parts relative to the transverse orbital sulcus.  The gyrus that lies between the olfactory sulcus and the medial orbital sulcus is often referred to as the medial orbital gyrus.  The cortex lying rostral to the transverse orbital sulcus and between the medial and lateral orbital sulci can be referred to as the anterior orbital gyrus and the cortex that lies caudal to it as the posterior orbital gyrus.  Lateral to the lateral orbital sulcus lies the orbital extension of the ventrolateral prefrontal cortex (i.e. the pars orbitalis of the inferior frontal gyrus).  

There are also one or two longitudinal sulci, named the intermediate orbital sulci (ios), lodged within the anterior orbital gyrus between the rostral parts of the medial and lateral orbital sulci.  Similarly, in some cases one or two posterior orbital sulci can be observed behind the transverse orbital sulcus within the posterior orbital gyrus between the caudal parts of the medial and lateral orbital sulci.  In some brains, a small dimple known as the sulcus fragmentosus can be identified between the olfactory sulcus and the medial orbital sulcus (Fig. 5). 

 

 


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