Other than the cerebrum, the cerebellum, the hypothalamus and the brainstem, what else is the brain made up of?

In the dorsal region of the diencephalon, there is a substantial mass of grey matter called the thalamus (a division of the forebrain). The cerebral cortex is reached by nerve fibres that emerge from the thalamus in all directions, enabling hub-like information exchanges. It performs a variety of tasks, including conveying sensory and motor information to the cerebral cortex and regulating awareness, sleep, and alertness. It is a paramedian symmetrical structure with left and right halves that is anatomically located between the cerebral cortex and the midbrain in the vertebrate brain. The major output of the diencephalon during embryonic development, it was initially identified by the Swiss embryologist and anatomist Wilhelm His Sr. in 1893.