Cerebral cortex

Show numbers

1. Central sulcus (of Rolando)

Shown in Image 1, this sulcus can be seen descending downwards to almost but not quite intersect with the lateral sulcus. The central sulcus divides the frontal lobe from the parietal lobe: in front is the appropriately named precentral gyrus of the frontal lobe and behind is the also appropriately named postcentral gyrus of the parietal lobe. This sulcus is named after Luigi Rolando, an Italian anatomist.

Show list

1.
Central sulcus (of Rolando)
2.
Postcentral gyrus
3.
Precentral gyrus
4.
Inferior parietal lobule
5.
Lateral sulcus (Sylvian fissure)
6.
Superior temporal gyrus
7.
Middle temporal gyrus
8.
Inferior temporal gyrus
9a.
Opercular part of inferior frontal gyrus
9b.
Triangular part of inferior frontal gyrus
9c.
Orbital part of inferior frontal gyrus
10.
Middle frontal gyrus
11.
Superior frontal gyrus
12.
Frontal pole
13.
Superior temporal sulcus
14.
Inferior temporal sulcus
15.
Cerebellum
16.
Superior parietal lobule (most of Brodmann's area 7)
17.
Supramarginal gyrus
18.
Angular gyrus
19.
Occipital pole
20.
Lateral occipital cortex
21.
Lateral occipital cortex - inferior division
22.
Orbital gyrus

In this view we see:

The right hemisphere covered by a thin layer of cerebral cortex less than half a centimetre thick.
The cerebral cortex is divided into frontal, parietal, temporal and occipital regions called lobes (described below).
The cortex is folded to fit within the confines of the skull, resulting in the surface of the brain appearing to be covered by ridges and crevices. The ridges are called gyri (singular: gyrus) and the crevices between the ridges are called sulci (singular: sulcus). A particularly deep crevice is called a fissure.
Below and towards the back (inferoposteriorly) is the much smaller cerebellum, located primarily underneath the occipital lobe.

Cerebral cortex consists of grey matter. The grey matter in the brain contains neurons, which are cells like the cells that make up our bodies, but unlike other cells neurons are specialised for receiving nerve impulses via a number of dendrites, and sending nerve impulses via a single long thread extending from the cell body called an axon.

Location

The frontal lobe is located behind the forehead underneath the frontal bone, anterior to the central sulcus and superior to the lateral sulcus. It is the largest lobe and covers much of the anterior half of the cerebral hemispheres.

Structure

This lobe contains the prefrontal cortex, motor cortex and orbitofrontal cortex and is divided into the precentral gyrus, and superior, middle and inferior frontal gyri by three sulci. The inferior frontal gyrus is subdivided into opercular, triangular and orbital subregions.

Structural differences enabled Korbinian Brodmann to describe distinct areas of the cerebral cortex. Notable in the frontal lobe are Brodmann’s area 4 (primary motor cortex), area 6 (premotor and supplementary motor cortex), and areas 44 and 45 (left hemisphere; together comprising Broca's language area). The large area anterior to areas 4 and 6 is prefrontal cortex, and the inferior surface of the frontal lobe is orbitofrontal cortex containing orbital gyri and the gyrus rectus. Between the orbital gyri and gyrus rectus are the olfactory bulb and tract.

Function

Movement – the primary motor cortex in the precentral gyrus is primarily concerned with the initiation of voluntary movements and is also the origin of about half of corticospinal (pyramidal) tractfibres. The premotor and supplementary motor cortex are also involved in the initiation of voluntary movement and have a role in preparing for and sequencing movement.

Thinking, memory and emotion – recent functional MRI (fMRI) studies have confirmed the role of the prefrontal cortex in executive functions such as planning, personality, social judgement and control of aggression. fMRI has also indicated the prefrontal cortex is involved in memory (working memory and retrieval of episodic memories) and emotion. Some of these functions are illustrated by the story of Phineas Gage and the injuries he suffered in 1848 as a result of an explosion which drove a metre long iron rod through his left prefrontal cortex.

Speech – Broca's area, usually in the left hemisphere, is located posteriorly in the inferior frontal gyrus and is important for the production of both spoken and written language.