The diencephalon is the part of the brain situated cranial to the midbrain. It contains the third ventricle and is divided into two symmetrical halves. The thalamus forms most of the lateral wall of the third ventricle and floor of the lateral ventricle. It receives sensory information from the body and transmits it to the cerebral cortex. The thalamus has two ends and four surfaces and contains nuclei that process different sensory modalities.