Where it is
- They sit at the base of the forebrain, deep to the cortex and next to the thalamus; the caudate nucleus lies nearest the midline, along the wall of the lateral ventricle, and the putamen and globus pallidus lie further out. [1][2]
- The internal capsule, a thick band of white matter, separates the caudate nucleus and the thalamus on its inner side from the putamen and globus pallidus on its outer side. [6]
- Outside the putamen lie, in order, the external capsule, the claustrum, the extreme capsule and then the insula, the cortex folded deep in the side of the brain. [7][8]
What it does
- They are linked to the control of voluntary movement, procedural learning, habit formation, conditional learning, eye movements, cognition and emotion. [1]
- OpenStax describes their most important function as planning movements: they help decide which movement goes ahead, with the cortex and cerebellum carrying it out. [2]
- The striatum (caudate nucleus and putamen) is the largest part and the main input: it receives signals from the cerebral cortex, the thalamus and dopamine fibres from the substantia nigra. [1][9]
Connections
- They work in a loop: cortex → striatum (caudate and putamen) → globus pallidus → thalamus → back to the cortex. In the usual model the direct pathway lets a chosen movement go ahead and the indirect pathway, through the subthalamic nucleus, holds back competing ones. [1][2]
- The internal segment of the globus pallidus and the reticular part of the substantia nigra are the main outputs; both are inhibitory and act on the thalamus. [1][10]
Other names
- Also called the basal nuclei: anatomists prefer “nuclei”, because a ganglion usually means a cluster of nerve cells outside the brain and spinal cord. [1][2]
- Striatum (dorsal striatum): the caudate nucleus and the putamen together, named for the striped look of the grey and white matter bridging them; the ventral striatum adds the nucleus accumbens and olfactory tubercle. [9][1]
- Lentiform (lenticular) nucleus: the putamen and the globus pallidus together, a lens-shaped mass with the putamen on the outside and the globus pallidus inside it. [11][7]
Size
- On this model the basal ganglia together fit in a box about 64 mm front to back, 37 mm top to bottom and 70 mm side to side (the box they fit in, not their volume). [5]
- Centre of the left putamen compared with the centre of the left globus pallidus: 4 mm further from the midline; 5 mm apart in a straight line. [5]
- Centre of the left caudate nucleus compared with the centre of the left putamen: 4 mm further back, 9 mm closer to the midline; 10 mm apart in a straight line. [5]