The cerebral cortex

Basic anatomy

The cerebral cortex or cerebrum is a structure within the brain that plays a key role in all that we do, think and feel.

The brain is divided into two halves or hemispheres, which are divided into four lobes (frontal, parietal, temporal and occipital) (Fig. 7.1). The left and right hemispheres are connected by the corpus callosum (Fig. 7.2), which facilitates communication between the two sides of the brain. The limbic system, sometimes referred to as a 5th lobe, forms the inner border of the cortex and is made up of several different structures scattered throughout the four lobes.

Figure 7.1 Anatomical map of the cerebral cortex – lateral surface.

Figure 7.2 Anatomical map of the cerebral cortex – medial surface.

Grey/white matter

The outermost layer of the cerebral cortex is termed the ‘grey matter’ (Fig. 7.2) and is primarily composed of the cell bodies of neurons (S2.6). The grey matter is an expansive sheet, approximately 2–4 mm (0.08–0.16 inches) thick, which is intricately folded to form grooves termed ‘sulci’ and raised areas termed ‘gyri’ (Fig. 7.2). The compact nature of the grey matter allows closer contact between neurons and consequently faster communication. The white matter (Fig. 7.2) below is formed predominantly by the myelinated axons of the neurons (S2.6), which connect to different regions of the central nervous system.

The internal capsule

The internal capsule lies superiorly to the thalamus (S2.9) and consists of neurons passing from the thalamus to the cerebral cortex and vice versa. Between the cortex and the internal capsule, the ascending and descending neurons form the corona radiata. All afferent and efferent information is routed through the internal capsule and most sensory information enters the cerebral cortex via the thalamus.