The subthalamic nucleus (STN) is a small lens-shaped nucleus just below the thalamus, above the substantia nigra of the midbrain and on the inner side of the internal capsule; one on each side. Anatomically it is the main part of the subthalamus; functionally it belongs to the basal ganglia. [1]
The 3D brain needs JavaScript. The text below still says where the subthalamic nucleus is and what it does.
The thalamus and midbrain are lit together; the subthalamic nucleus is not drawn on its own. The front (coronal) slice button cuts through them. Drag to turn, pinch or scroll to zoom, tap any part to name it; .
Not a separate shape in this atlas; lit: the part that holds it. Lit: the whole thalamus and midbrain, on both sides. The subthalamic nucleus lies between these two lit parts: under the thalamus and above the substantia nigra at the top of the midbrain. It is small and lens-shaped and it has no shape of its own in the BodyParts3D model, so nothing is drawn at a guessed point. [1]
Lit here: the thalamus and the midbrain, the parts the subthalamic nucleus lies between — see each on its own page.
As its name says, it lies below (ventral to) the thalamus; it is above (dorsal to) the substantia nigra and on the inner side (medial) of the internal capsule. [1]
It is the main part of the subthalamus, the part of the diencephalon under the thalamus. [1][2]
Small: about 158 mm³ in humans, against about 808 mm³ for the external globus pallidus, its partner. [1]
It is one of the main parts of the basal ganglia, with the striatum (caudate nucleus and putamen), the globus pallidus and the substantia nigra, and lies further back than the striatum and pallidum. [3][4]
What it does
It is the excitatory part of the basal ganglia core: its main neurons use glutamate and excite their targets, and for 82.7% of traced neurons (in macaques) the main target is the internal globus pallidus. [1]
It takes part in the “indirect” and “hyperdirect” pathways of movement control; the direct pathway, from the striatum straight to the internal pallidum, bypasses it. [1]
It is required for intended movement, including walking, balance and coordination, and is involved in stopping or interrupting a movement already under way. [1]
Its neurons fire on their own, with no input: “fast-spiking pacemakers” at 80 to 90 times a second in primates. With the external globus pallidus it is thought to form a central pacemaker of the basal ganglia. [1]
Connections
Main input: inhibitory (GABA) fibres from the external globus pallidus. Excitatory input comes from the whole frontal cortex, mostly its motor, premotor and eye-movement areas, and dopamine input from the substantia nigra. [1][4]
Its outputs, all excitatory, leave from its top and go mainly to both parts of the globus pallidus and to the substantia nigra; about 17% of neurons (in macaques) also reach the striatum. [1]
Other names
Abbreviated STN; also the nucleus of Luys, after Jules Bernard Luys, who first described it in 1865, and the older corpus Luysi or Luys’ body. [1]
Size
The model has no shape for the subthalamic nucleus itself, so it is not measured here. The left thalamus that holds it measures about 37 mm front to back, 24 mm top to bottom and 24 mm side to side on this model (the box it fits in, not its volume). [5]
The model has no shape for the subthalamic nucleus itself, so it is not measured here. The midbrain that holds it measures about 29 mm front to back, 17 mm top to bottom and 29 mm side to side on this model (the box it fits in, not its volume). [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.