The lateral geniculate body (lateral geniculate nucleus) is a small oval bump on the underside of the back of each thalamus, where the optic tract ends; there is one on the left and one on the right. It is the thalamus’s relay for sight, passing signals from the eyes on to the primary visual cortex at the back of the brain. [1]
The 3D brain needs JavaScript. The text below still says where the lateral geniculate body is and what it does.
Slice
Opens cut by a front (coronal) slice through the lateral geniculate body. Drag to turn, pinch or scroll to zoom, tap any part to name it; .
Takes part in: vision — see every part of each lit together.
Where it is
A small, oval projection on the underside (ventral side) of the thalamus, where the thalamus meets the visual pathway from the eye; there are two, one on each side. [1]
With the medial geniculate body it forms the metathalamus, at the back of the thalamus. [2]
The brachium of the superior colliculus, a band of fibres from the midbrain, runs partly into it and partly into the optic tract. [3]
What it does
Its main neurons receive the retina’s signals directly through the optic tract and send them on through the optic radiation to the primary visual cortex (V1). [1]
Each one handles only one half of the visual field, but from both eyes: the eye on the same side feeds layers 2, 3 and 5, the eye on the opposite side layers 1, 4 and 6. [1]
Colour processing starts here: the parvocellular (P) cells carry red–green opponent signals, the koniocellular (K) cells mostly blue–yellow, and the magnocellular (M) cells mostly brightness. [1]
Honest limit: it is far more than a relay; the retina supplies only a small share of its input, and as much as 95% comes from the visual cortex, the superior colliculus, the pretectum, the thalamic reticular nucleus and local interneurons. [1]
Connections
In: retinal ganglion cells through the optic tract, and strong feedback from the primary visual cortex. [1]
Out: the optic radiation, which runs in the back (retrolenticular) part of the internal capsule to layer 4 of V1; the koniocellular cells project mainly to layers 2 and 3. [1]
Inside it
Six layers of neurons alternating with optic fibres: magnocellular layers 1–2 and parvocellular layers 3–6, with koniocellular cells between the layers. [1]
Each one averages about 118 mm³ in an adult, the volume of a cube 4.9 mm on a side; a study of 24 hemispheres found 91 to 157 mm³, about 28 mm³ of it magnocellular and 90 mm³ parvocellular layers. [1]
On this model the left lateral geniculate body measures about 11 mm front to back, 7 mm top to bottom and 8 mm side to side (the box it fits in, not its volume); the right one is its mirror image. [4]
Centre of the left lateral geniculate body compared with the centre of the left medial geniculate body: 6 mm further from the midline; 6 mm apart in a straight line. [4]
Centre of the left lateral geniculate body compared with the centre of the left occipital lobe: 60 mm further forward, 4 mm further from the midline; 61 mm apart in a straight line. [4]
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.