Side by side
| Compared | Thalamus | Hypothalamus |
|---|---|---|
| Where it is | The upper (dorsal) part of the diencephalon. Paired: the inner surface of each thalamus forms the upper part of a side wall of the third ventricle. [2][5] | Below the thalamus, the bottom (basal) part of the diencephalon. On the midline: it lines the lower front side walls of the third ventricle, below the groove that separates it from the thalamus. [1][5] |
| What it does | Relays sensory and motor signals to the cerebral cortex; every sense except smell passes through it on the way to the cortex. [2][6] | Links the nervous system to the endocrine system through the pituitary gland: it makes releasing hormones for the anterior pituitary, and oxytocin and vasopressin that are released from the posterior pituitary. [1] |
| Connects with | Fibres fan out to the whole cerebral cortex and every cortical region studied sends fibres back; it also receives the output of the basal nuclei and of the cerebellum. [2][6][7] | The pituitary gland, through the infundibulum; the hippocampus, through the fornix to its mammillary bodies; the amygdala, through the stria terminalis. [5][8][9] |
| Size measured from the model | 37 mm front to back, 24 mm top to bottom, 24 mm side to side [4] | 18 mm front to back, 20 mm top to bottom, 17 mm side to side [4] |
Size is the box each part fits in on this one model (left thalamus; hypothalamus), not its volume. Real brains vary. A part that comes as a left and a right copy is measured on its left copy; the right one mirrors it.
How far apart are they?
Measured from the model [4], from the left thalamus to the hypothalamus:
- Centre to centre: 28 mm in a straight line.
- The centre of the hypothalamus is 22 mm further forward, 12 mm lower and 13 mm closer to the midline than the centre of the left thalamus.
- Nearest points of the two shapes: about 3 mm apart.
A “centre” here is the average position of the points on the part’s 3D surface, so for a curved part such as a C shape it can sit outside the part itself. The nearest-points figure is measured between the corners of the simplified meshes, so a gap of 2 or 3 mm or less is within the model’s coarseness: read it as “touching or nearly so”.