Paleoencephalon is a term used in neuroscience to describe a part of the brain that evolved millions of years ago. However, there are many synonyms for this complex term that can help simplify its meaning. One such synonym is the "paleocortex," which refers to the oldest part of the cortex that evolved early in vertebrate evolution. Another synonym is the "archipallium," which is also a term used to describe the oldest part of the cerebral cortex. These synonyms help researchers and students better understand the ancient parts of the brain and how they relate to modern neurological function.