Super detailed video
Hippocampus is a complex brain structure embedded deep into temporal lobe (so of course one part in cerebral cortex). It has a major role in learning and memory.
Thalamus is a paired gray matter structure of the diencephalon (which consists of thalamus and hypothalamus, and of course belongs to forebrain but differ to telencephalon contributing to cerebral cortex) located near the center of the brain. It is above the midbrain or mesencephalon, allowing for nerve fiber connections to the cerebral cortex in all directions — each thalamus connects to the other via the interthalamic adhesion.
The midbrain is the topmost part of the brainstem, the connection central between the brain and the spinal cord. There are three main parts of the midbrain - the colliculi, the tegmentum, and the cerebral peduncles.
Those relations can be clearly observed as earily as GW5 in human brain (spatial relationship)
