Final answer:
The diencephalon is positioned between the brain stem and the cerebrum, making the statement true. The diencephalon includes the thalamus and hypothalamus, important for relaying information and coordinating homeostatic functions, respectively.
Step-by-step explanation:
The diencephalon is indeed located between the brain stem and the cerebrum; therefore, the correct answer to the statement is a. True. The diencephalon is an important region of the adult brain that retains its embryological name due to its role as a passage or connection between the cerebrum and the rest of the nervous system. This excludes the system associated with olfaction, as the sense of smell connects directly with the cerebrum. It is composed mainly of the thalamus and hypothalamus, which form the walls of the third ventricle. Other notable structures included in the diencephalon are the epithalamus, containing the pineal gland, and the subthalamus, featuring the subthalamic nucleus, part of the basal nuclei.