Superolateral surface of cerebral hemisphere

The superolateral surface of cerebral hemisphere is characterized by various sulci and gyri. The two major sulci are the central sulcus and lateral sulcus.

The lateral sulcus is a deep fissure that starts on the underside of the brain, and extends on to the superolateral surface of cerebral hemisphere. It separates the frontal and parietal lobes on the upper side from the temporal lobe below. By pulling apart the superior and inferior lips (or opercula) of the lateral sulcus, we can reveal the insular cortex (or insula) hidden within the depths of the lateral fissure. The insula is often associated with emotion and the limbic system. As the lateral sulcus reaches the superolateral surface of cerebral hemisphere, it divides into three branches or rami: the anterior horizontal, anterior ascending, and posterior rami. These branches create additional gyri. Running through the lateral sulcus is the middle cerebral artery, which emerges from the circle of Willis and runs through the lateral sulcus to reach on to the superolateral surface of cerebral hemispheres.

Another important sulcus called the central sulcus, can be observed descending obliquely downwards from the medial margin on the superolateral surface of cerebral hemisphere. This particular sulcus separates the frontal motor cortex, located in the front, from the parietal sensory cortex, situated at the back. Two other significant sulci running, the pre-central sulcus at the front and the post-central sulcus at the back, run alongside the central sulcus. In between the central and pre-central sulci lies the pre-central gyrus, which serves as the primary motor cortex (known as Broadman’s area 4). Similarly, between the central and post-central sulci is the post-central gyrus, which acts as the primary sensory cortex (Broadman’s areas 3, 1, 2).

The primary motor and sensory areas are mapped on the pre- and post-central gyri as motor and sensory homunculi, wherein face and upper body are represented on the superolateral surface of cerebral hemisphere, while the lower legs are represented on the medial surface. Therefore, a stroke affecting the middle cerebral artery, which is a major supplier of blood to the superolateral cortex, could result in weakness and loss of sensation in the upper limbs and face, while leaving the leg region unaffected.

Moving towards the back, we can see another important sulcus called the parieto-occipital sulcus. This sulcus extends to the inner surface of the brain and separates the cuneus in the occipital lobe from pre-cuneus in the parietal lobe.

In addition, there are other sulci such as the superior and inferior frontal sulci within the frontal lobe, which create three gyri known as the superior, middle, and inferior frontal gyri. The parietal lobe is divided into the superior and inferior parietal lobules by the intraparietal sulcus. Within the temporal lobe on the lateral surface, there are the superior and inferior temporal sulci, which divide the lobe into superior, middle, and inferior temporal gyri.

The pre-frontal cortex, located at the front, is responsible for higher-order motor organization. On the other hand, the posterior the parieto-occipito-temporal region represents the higher-order sensory organizational part of the cerebral cortex.