Anatomy of Cortex

The neocortex is the most phylogenetically developed structure of the human brain as compared with the brains of other species. The complex pattern of folding allows an increased cortical surface to occupy a smaller cranial volume. The pattern of folding that forms the sulcal and gyral patterns remains highly preserved across individuals. This enables a nomenclature for the cortical anatomy.

The left and right cerebral hemispheres are separated by the longitudinal cerebral fissure. The principal connection between the 2 hemispheres is the corpus callosum. Each cortical hemisphere can be divided into 4 lobes: frontal, temporal, parietal, and occipital. The frontal lobe can be distinguished from the temporal lobe by the lateral sulcus (Sylvian fissure). The frontal lobe can be distinguished from the parietal lobe by the central sulcus (Rolandic fissure). The parieto-occipital sulcus, which is visible on the medial aspect of the hemisphere, divides the parietal and occipital lobes. Within the lateral sulcus is another cortical surface referred to as the insula.

The frontal lobe can then be further divided into the superior, middle, and inferior frontal gyri, which are divided by the superior and inferior frontal sulci, respectively. The inferior frontal gyrus forms the frontal operculum, which overlies the lateral sulcus. The frontal operculum can be divided into 3 triangular gyri: the pars orbitalis, the pars triangularis, and the pars opercularis, in order from anterior to posterior. The precentral gyrus is the gyrus immediately anterior to the central sulcus.

Similarly, the temporal lobe is divided into the superior, middle, and inferior temporal gyri, which are separated by the superior and inferior temporal sulci. On the inferior surface of the temporal lobe just lateral to the midbrain the parahippocampal gyrus can be identified, with the collateral sulcus lying lateral. Between the parahippocampal gyrus and the inferior temporal gyrus lies the occipitotemporal gyrus, also known as the fusiform gyrus.

Within the parietal lobe, the superior temporal sulcus is capped by the angular gyrus. Just above this, the lateral sulcus is capped by the supramarginal gyrus. Just below the angular gyrus, the lateral occipital gyrus caps the inferior temporal sulcus.