Answer. The central sulcus.
Brief Discussion
The central sulcus is a key surface anatomy landmark in neuroradiology as it divides the primary somatomotor cortex and primary somatosensory cortex. It also divides the frontal and parietal lobes.
There are 4 general methods that can be used to identify the central sulcus. These include:
1. Recognition of intrinsic features such as the curvature and extent
2. Recognition of an adjacent gyrus with a known relationship to the central sulcus
3. Recognition of an adjacent sulcus with a known relationship to the central sulcus
4. Use of side-to-side symmetry
There are numerous anatomic signs related to each of these three methods on either axial or sagittal images that are very helpful for central sulcus recognition. See the essentials modules for further detail.