Corpus callosum

Parts

The corpus callosum is divided into four parts: rostrum, genu, body/trunk and splenium

• The rostrum is the thin, beak-like anterior-inferior part of the corpus callosum. It is continuous with the lamina terminalis and connects the orbital (ventral prefrontal) surfaces of the frontal lobes.
• The genu is the anterior, curved part of the corpus callosum. It connects the medial and lateral prefrontal cortices, through a bundle of fibers that is called forceps minor (frontal forceps).
• The body or trunk forms the largest, central section. Its fibers pass through the corona radiata (a white matter structure) to connect various cortical regions, mainly in the frontal and parietal lobes.
• The splenium is the thick, posterior part that tapers away caudally. It connects the visual and occipital cortices, through the forceps major (occipital forceps). 

There are also other white matter fibres projecting rostral to the forceps major, which are known as the tapetum. These fibers spread laterally and form a roof over the temporal horns of the lateral ventricle.

The forceps major, the forceps minor and the tapetum are all parts of the radiation of the corpus callosum. The radiation of the corpus callosum, connects the two cerebral hemispheres through the corpus callosum. Broadly speaking there are two types of connections: homotopic and heterotopic.

Homotopic connections link similar regions from the left and right sides of the brain (e.g. left and right motor cortex), while heterotopic connections link dissimilar areas of the left and right hemispheres (e.g. frontal to parietal). All of these connections play an important role integrating and supporting the majority of the brain functions. 

Learn everything about the corpus callosum and surrounding structures with our study unit, or take our quiz to see what you already know:

Functions

The primary function of the corpus callosum is interhemispheric communication, connecting both similar (homotopic) and different (heterotopic) areas. The rostrum and genu link prefrontal regions of the frontal lobes; the body connects frontal, parietal and temporal lobes of the two hemispheres; the splenium mainly connects the two occipital lobes and the temporal lobes to a lesser extent. This communication between the two hemispheres coordinates the different functions, either by integrating the sensory information, or by harmonizing the motor and cognitive functions. 

Besides its importance in communication, the corpus callosum plays a key role in cognition by linking distributed neural networks. Emerging evidence suggests that weakened integrity of the callosum contributes to a decline in cognitive function in aging adults. On the flip side, increased callosal thickness in typical childhood development correlates with intelligence, processing speed and problem-solving abilities. 

You've almost finished revising the corpus callosum anatomy... but how's your knowledge of the other parts of the brain? Find out with our free brain quizzes and labeled diagrams! 

Surrounding structures

Superior to the body of the corpus callosum lies the longitudinal (interhemispheric) fissure containing the falx cerebri (a fold of the dura mater), as well as the anterior cerebral vessels. The superior aspect of the corpus callosum is covered with a thin layer of glial tissue known as the indusium griseum, over which run the longitudinal striae which are narrow strips of gray matter on either side of the midline, remnants of limbic development.

The cingulate gyrus, a limbic structure involved in emotion and memory, lies superior to the corpus callosum, separated by the callosal sulcus. The anterior part of the corpus callosum (rostrum, genu, body) is attached inferiorly to the fornix by the septum pellucidum, while the splenium is attached inferiorly to the crura and the commissure of the fornix.

If you would like to challenge yourself even further, try out our quiz on the structures seen on the medial view of the brain.

Blood supply

The corpus callosum has a rich blood supply which is reinforced by anastomoses, making infracts uncommon for this structure. 

The pericallosal artery, which is the distal continuation of the anterior cerebral artery, is the main artery that supplies the corpus callosum. It arches over the corpus callosum, running from the subcallosal area (below the rostrum) and supplying the rostrum, genu and body. Throughout its course, it gives off long and short callosal branches that supply blood to the above parts of the corpus callosum. 

The posterior pericallosal (splenial) artery, typically a branch of the posterior cerebral artery, bifurcates into an inferior and a superior branch, which supply the inferior and superior part of the splenium respectively. The superior branch usually anastomoses with the pericallosal artery.

In a significant percentage of individuals, the corpus callosum also gets blood supply from the anterior communicating artery, either via the subcallosal artery or the median callosal artery. The subcallosal artery supplies the hypothalamus in part, but also supplies the rostrum and genu of the corpus callosum. The median callosal artery is very similar to the subcallosal artery, but it runs further in order to reach the body of the corpus callosum.

You can test yourself on the arteries of the brain with our quiz.