Frontal Lobe
The superolateral surface is bordered posteriorly by the central sulcus. It presents:
- the superior frontal gyrus
- the middle frontal gyrus
- the inferior frontal gyrus
- and the superior, middle, and inferior frontopolar gyri
- the precentral gyrus.
The lateral surface is crossed by the following sulci:
- the precentral sulcus
- the superior frontal sulcus
- the inferior frontal sulcus
Superolateral surface of the frontal lobe
Superior frontal sulcus
The sulcus that separates the superior frontal gyrus from the middle frontal gyrus inferiorly on the lateral surface of the frontal lobe. It runs parallel to the interhemispheric fissure.
Inferior frontal sulcus
The sulcus arising from the inferior segment of the precentral sulcus that constitutes the inferior border of the middle frontal gyrus and the superior border of the inferior frontal gyrus. It may continue anteriorly as the lateral orbital sulcus.
Superolateral surface of the frontal lobe
Superior frontal gyrus
The gyrus constitutes the upper and medial portion of the frontal lobe. Its superior limit is represented by the superior margin of the lobe, whereas the inferior one is the superior frontal sulcus. It is limited posteriorly by the precentral sulcus, and medially by the cingulate sulcus
Superior frontal gyrus
Anteriorly, it continues into the medial orbito-frontal gyrus on the medial surface, sometimes being separated from it by the supraorbital sulcus, and into the superior frontopolar gyrus on the lateral surface /anterior view/.
Middle frontal gyrus
The gyrus included by the superior and inferior frontal sulcus. It is placed anteriorly to the precentral gyrus and corresponds to the cingulate gyrus on the medial surface. It can be divided in a superior and inferior parts by a horizontal sulcus which can be originated by the frontomarginal sulcus.
Inferior frontal gyrus
The gyrus is located on the inferolateral surface of the lateral convexity of the frontal lobe. It is located between the inferior frontal sulcus and the circular sulcus of the insula. It is bordered posteriorly by the inferior segment of the precentral sulcus and the anterior portion of the subcentral gyrus.
Inferior frontal gyrus
Inferior frontal gyrus
It is further divided into three portions by the horizontal and ascending rami of the Sylvian fissure: the pars orbitalis /red/, the pars triangularis /green/, and the pars opercularis /purple/.
Pars orbitalis
The most anterior portion of the inferior frontal gyrus bordered posteriorly by the horizontal or anterior ramus of sylvian fissure and located above the orbit. It continues inferiorly into the lateral orbital gyrus
Pars triangularis
The middle portion of inferior frontal gyrus that lies between the horizontal and ascending rami of the sylvian fissure. It contributes to composing the frontal operculum.
Pars opercularis
The posterior portion of the inferior frontal gyrus lying between the ascending ramus and the posterior ramus of the sylvian fissure. It has a typical U shape and participates to form the central operculum
Central region
Precentral sulcus
The sulcus running parallel to the central sulcus, and anterior to it. It separates the three horizontal frontal gyri from the vertical precentral gyrus. It is discontinuous and formed by superior and inferior precentral segments related to the superior and inferior frontal gyri.
/Occasionally it presents an accessorial sulcus, the intermediate precentral segment, placed between the precentral gyrus and the middle frontal gyrus/
Precentral gyrus
The only vertical gyrus on the frontal convexity, also known as prerolandic gyrus. It is placed between the precentral and the central sulci. On the inferior surface, it faces the Sylvian fissure and is limited medially by the cingulate lobe. The connection to the postcentral gyrus is made up by the subcentral lobule, inferiorly, and the paracentral lobule, superiorly.
On axial imaging, the superior frontal sulcus intersects the precentral gyrus forming an inverted greek letter omega Ω.
Subcentral gyrus
The connection between the frontal and the parietal lobes. It is located below the central sulcus, where the precentral gyrus merges into the inferior portion of the postcentral gyrus. It is bordered inferiorly by the sylvian fissure.
Frontomarginal sulcus
The horizontal sulcus on the anterior surface of the frontal pole. It is limited superiorly by the inferior frontal and the frontopolar gyri; inferiorly by the frontomarginal gyrus.
Frontomarginal gyrus
The horizontal gyrus is placed under the frontomarginal sulcus, at the edge between the lateral and the basal surfaces of the frontal lobe.
Superior frontopolar sulcus
The horizontal groove on the frontal pole separating the inferior portion of the superior frontal gyrus from the superior frontopolar gyrus.
Superior frontopolar gyrus
The most superior gyrus of the frontal pole. It is located between the superior frontal gyrus, superiorly, and the middle frontopolar gyrus, inferiorly. It is bordered laterally by the superior frontal sulcus.
Middle frontopolar gyrus
The groove is located between the superior and inferior frontopolar gyri. It stops laterally at the level of the middle and inferior frontal gyri.
Inferior frontopolar gyrus
The most inferior gyrus of the frontal pole. It is located between the inferior frontopolar sulcus superiorly and the frontomarginal sulcus.
Temporal Lobe
The superolateral surface is divided into three gyri by the superior and inferior temporal sulcus. These horizontal gyri, from superior to inferior, are:
- superior temporal gyrus
- middle temporal gyrus
- inferior temporal gyrus
In front of this area, there is the temporal pole. All this region is characterized by a lot of sulcal bridges
Superolateral surface of the temporal lobe
Superior temporal sulcus
The horizontal sulcus parallel to the Sylvian fissure separating the superior temporal gyrus from the middle temporal gyrus. It ends at the level the angular gyrus and is formed by ventral and caudal rami. The ventral ramus splits the temporal lobe, the caudal ramus can be further divided into the ascending, also called sulcus angularis, and horizontal segments.
Inferior temporal sulcus
The sulcus placed between the middle and the inferior temporal gyri. Its caudal tract can form the anterior occipital sulcus, connecting the inferior temporal sulcus to the lateral occipital sulcus
Superolateral surface of the temporal lobe
Superior temporal gyrus
The most cranial gyrus of the temporal lobe represents the temporal operculum. The superior margin is the sylvan fissure, which separates it from the inferior portion of the frontal and parietal lobes. The inferior border is the superior temporal sulcus. Posteriorly it continues into the supra marginal and angular gyri.
On the medial surface, it is limited, from posterior to anterior, by the limiting (circular) sulcus of the insula and the sylvian fissure.
Middle temporal gyrus
The gyrus of the temporal lobe bordered superiorly by the superior temporal sulcus and inferiorly by the inferior temporal sulcus. It extends from the temporal pole to the occipital pole and covers the temporal horn of the lateral ventricle.
Inferior temporal gyrus
The gyrus is located between the inferior temporal sulcus and the inferolateral margin of the cerebral hemisphere. Therefore, it has a basal surface on the inferior surface of the temporal lobe: the occipitotemporal sulcus separates it from the fusiform gyrus. Posteriorly, it is separated from the occipital lobe by the temporo-occipital notch.
Sylvian surface
The Sylvian part of the medial surface is divided, from anterior to posterior, into three areas thanks to the transverse temporal sulcus: the planum polare, the transverse temporal gyrus, and the planum temporale.
Transverse temporal sulcus
The small sulcus which arises from the lateral fissure separating the transverse temporal gyrus from the planum temporale.
Transverse temporal gyrus
The area constituting the dorsal portion of the superior temporal gyrus, also known as Heschl’s gyrus. It is bordered anteriorly by the planum polare, posteriorly by the planum temporale. Occasionally, it can be divided by an intermediate transverse sulcus in anterior and posterior transverse temporal gyri.
Planum temporale
The area which forms the most caudal portion of the dorsal surface of the superior temporal gyrus. It is placed posteriorly to the Heschl’s gyrus. Sometimes it is divided into vertical and horizontal segments.
Planum polare
The dorsal portion of the superior temporal gyrus is placed anteriorly to the Heschl’s gyrus, in front of the transverse temporal sulcus, and it forms the rostral portion of the superior temporal gyrus. It is bounded medially by the parahippocampal gyrus.
Parietal Lobe
The superolateral surface of the parietal lobe is limited by the central sulcus anteriorly and by the parieto-occipital sulcus posteriorly. Inferiorly it is bordered by the posterior ramus of the Sylvian fissure and by an undefined sulcus of the occipital and temporal lobes.
The surface presents two main sulci:
- the postcentral sulcus, which is parallel to the central sulcus
- the intraparietal sulcus.
These sulci form three main gyri:
- the postcentral gyrus
- the superior and inferior parietal lobules.
The inferior lobule is divided into two portions: the supramarginal and the angular gyri. This surface is connected to the frontal lobe through the paracentral and subcentral gyrus.
Central region
Postcentral sulcus
The vertical groove, parallel to the precentral sulcus, which limits posteriorly the post central gyrus. It is the anterior border of the superior parietal lobule and the supra marginal gyrus.
Postcentral gyrus
The gyrus is located between the central and postcentral sulci. Occasionally it can be divided in two or more parts. Inferiorly, it is limited by the Sylvian fissure. It is connected to the frontal lobe by the subcentral gyrus and the paracentral lobule.
Superolateral surface of parietal lobe
Intraparietal sulcus
The horizontal groove separating the superior and the inferior parietal lobules. it is located at the level of the superior temporal line. It starts from the postcentral sulcus and it continues as the superior occipital sulcus. Numerous unnamed segments arise from this fissure, but It is often possible to recognize three different parts: the anterior, intermediate, and posterior segments.
Superior parietal lobule
The lobule is located between the superior margin of the parietal lobe and the intraparietal sulcus. It is connected to the superior occipital gyrus by a transition area known as arcus parieto-occipitale.
Inferior parietal lobule
The lobule is located between the superior parietal lobule, superiorly, and the Sylvian fissure, inferiorly, which forms the parietal operculum. It is divided into two different gyri: the anterior supramarginal gyrus and the posterior angular gyrus. Posteriorly, the parieto-occipital sulcus constitutes the limit with the occipital lobe.
Inferior parietal lobe
Supramarginal gyrus
The anterior part of the inferior parietal lobule. It is limited superiorly by the intraparietal sulcus which separates it from the superior parietal lobule. Anteriorly it encircles the caudal part of the sylvian fissure, behind the postcentral gyrus, and it continues into the superior temporal gyrus. Posteriorly, the intermediate sulcus separates it from the angular gyrus.
Angular gyrus
The posterior portion of the inferior parietal lobule. Rostrally, the intermediate sulcus separates it from the supramarginal gyrus. Inferiorly, it is bounded by the superior temporal sulcus, continuing into the caudal portion of the superior and the middle temporal gyri. Posteriorly, the parietal-occipital sulcus lies between the posterior portion of the angular gyrus and the superior occipital gyrus.
Occipital Lobe
The superolateral surface presents a horizontal sulcus, called the lateral occipital sulcus, which limits :
- the superior occipital gyrus
- the inferior occipital gyrus
The lateral surface turns medially as the posterior surface, which corresponds to the convexity of the occipital pole.
The superolateral surface of the occipital lobe
Superior occipital sulcus
The sulcus arising from the posterior segment of the intraparietal sulcus, also known as intraoccipital sulcus, which runs parallel to the interhemispheric fissure. It intersects, forming an angle of 90 degrees, the transverse occipital sulcus, separating the superior occipital gyrus from the middle occipital gyrus.
Transverse occipital sulcus
The fissure on the dorsal surface of the occipital lobe starting from the posterior segment of the parieto-occipital sulcus. It separates the middle occipital gyrus from the middle temporal gyrus.
Lunate sulcus
The vertical sulcus on the lateral occipital surface, perpendicular to the lateral occipital sulcus. It can be divided into dorsal and ventral branches.
Inferior occipital sulcus
The small horizontal sulcus on the inferior surface of the lobe. It separates the middle and the inferior occipital gyri.
Lateral occipital sulcus
The horizontal fissure that divides the middle occipital gyrus into the superior and inferior portions. It often arises from the middle segment of the lunate sulcus, and anteriorly it can be connected to the inferior temporal sulcus.
Anterior occipital sulcus
The small fissure that may arise from the preoccipital notch, connecting the inferior temporal sulcus and the lateral occipital sulcus.
Superolateral surface of the occipital lobe
Superior occipital gyrus
The sulcus on the occipital lobe limited superiorly by the transverse occipital sulcus, laterally by the superior occipital sulcus, and medially by the cuneus.
Inferior occipital gyrus
The lowest gyrus on the lateral surface of the occipital lobe. it is separated from the middle occipital gyrus by the inferior occipital sulcus.
Lateral occipital gyrus
The gyrus is limited by the superior occipital gyrus, medially, and the inferior occipital gyrus, laterally, also called middle occipital gyrus. It is bordered anteriorly by transverse occipital sulcus and posteriorly by the lunate sulcus.
