The medial geniculate body (medial geniculate nucleus) is a small oval bump on the underside of the back of each thalamus, just inside the lateral geniculate body and to the side of the superior colliculus. It is the thalamus’s relay for hearing, passing sound signals from the inferior colliculus on to the auditory cortex. [1][2]
The 3D brain needs JavaScript. The text below still says where the medial geniculate body is and what it does.
Slice
Opens cut by a front (coronal) slice through the medial geniculate body. Drag to turn, pinch or scroll to zoom, tap any part to name it; .
Takes part in: hearing — see every part of each lit together.
Where it is
Part of the auditory thalamus, one on each side, lying to the side (lateral) of the superior colliculus. [1][2]
With the lateral geniculate body it forms the metathalamus, at the back of the thalamus. [3]
The brachium of the superior colliculus passes to the thalamus between it and the pulvinar. [2]
What it does
The last relay below the cortex on the hearing path: it receives the inferior colliculus’s output and passes it to the auditory cortex. [1][4]
Its ventral division relays the pitch, loudness and two-ear information of sounds and is laid out by pitch, with low frequencies at the side and high frequencies toward the middle. [1]
Its dorsal and medial divisions also take non-hearing input; some cells answer to touch as well as sound, and the medial division tracks the relative loudness and duration of a sound. [1]
It is thought to influence where attention is directed and how long it is held. [1]
Connections
In: the inferior colliculus of the same side; its central nucleus feeds the ventral division. [4]
Out: the auditory cortex, and feedback down to the inferior colliculus. [1][4]
Inside it
Three main divisions, ventral, dorsal and medial, told apart by their cells, their connections and how their neurons respond; only the ventral division handles hearing alone. [1]
On this model the left medial geniculate body measures about 7 mm front to back, 8 mm top to bottom and 7 mm side to side (the box it fits in, not its volume); the right one is its mirror image. [5]
Centre of the left medial geniculate body compared with the centre of the left lateral geniculate body: 6 mm closer to the midline; 6 mm apart in a straight line. [5]
Centre of the left medial geniculate body compared with the centre of the left inferior colliculus: 4 mm further forward, 7 mm higher, 12 mm further from the midline; 14 mm apart in a straight line. [5]
Facts describe anatomy and normal function only. The 3D model is the adult male BodyParts3D brain (credits and licence); real brains vary in size and shape, so its measurements describe one model, not anyone’s brain.