Side by side
| Compared | Superior colliculus | Inferior colliculus |
|---|---|---|
| Where it is | The upper pair of bumps on the back of the midbrain, below the pineal gland and the thalamus, behind the cerebral aqueduct. [2][1] | The lower pair of bumps on the back of the midbrain, just below the superior colliculi and above the point where the trochlear nerve leaves the brainstem. [3] |
| What it does | Directs head and eye movements toward targets; its upper layers map what is seen, and its deeper layers also bring in hearing and touch to steer gaze, including the fast eye jumps called saccades. [2] | The principal midbrain nucleus of the hearing pathway: nearly every rising auditory pathway meets here, and it takes part in locating sounds and in telling pitches apart. [3] |
| Connects with | Its upper layers receive direct input from the retina and from the visual cortex; its output goes to brainstem and spinal centres that move the eyes and head (the tectospinal tract) and to the thalamus. [2][5] | Receives input from many brainstem hearing nuclei through the lateral lemniscus and sends its output through the brachium of the inferior colliculus to the medial geniculate nucleus of the thalamus, which relays it to the auditory cortex. [3][6] |
| Size measured from the model | 6 mm front to back, 6 mm top to bottom, 8 mm side to side [4] | 8 mm front to back, 8 mm top to bottom, 8 mm side to side [4] |
Size is the box each part fits in on this one model (left superior colliculus; left inferior colliculus), 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 superior colliculus to the left inferior colliculus:
- Centre to centre: 8 mm in a straight line.
- The centre of the left inferior colliculus is level front to back, 8 mm lower and the same distance from the midline than the centre of the left superior colliculus.
- Nearest points of the two shapes: about 2 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”.