Lateral sulcus

One of the most prominent sulci of the human brain, the lateral sulcus (= Sylvian fissure = lateral fissure) separates the superior border of the temporal lobe from the inferior border of the frontal and parietal lobes.

The regions of the temporal, parietal, and frontal lobes that immediately surround the lateral sulcus collectively form the operculum (“little lid”) of the insula.  If you place your fingers in the lateral sulcus and gently separate the temporal lobe from the frontal and parietal lobes, you’ll see the insular cortex, a deep region of the cortex that is often referred to as the fifth lobe.  You’ll also have a good view of the course of the middle cerebral a.