The shallow grooves on the surface of the brain are called sulci. These grooves help to increase the surface area of the cerebral cortex, allowing for more neurons to be packed into the skull. The raised ridges between the sulci are known as gyri. Together, sulci and gyri form the characteristic folded appearance of the brain.
Other terms mentioned in the question refer to different structures:
- Ventricles are fluid-filled cavities within the brain.
- Fissures are deeper grooves that separate larger regions of the brain, such as the longitudinal fissure that divides the two cerebral hemispheres.
- Folia are the folds found in the cerebellum.
Therefore, the correct answer is c) sulci.