All parts of the brain › Substantia nigra

Where is the substantia nigra?

The substantia nigra is a band of grey matter in the midbrain, at the top of the brainstem: the largest nucleus there, lying just behind (dorsal to) the cerebral peduncles, one on each side of the midline. It counts as part of the basal ganglia. [1]

Not a separate shape in this atlas; lit: the part that holds it. Lit: the whole midbrain. Each substantia nigra is a band inside the midbrain, just behind the cerebral peduncle on its own side; the band itself has no shape in the BodyParts3D model, so nothing is drawn at a guessed point. [1][2]

The 3D brain needs JavaScript. The text below still says where the substantia nigra is and what it does.

Slice

Opens cut by a side (sagittal) slice through the midbrain, which holds the substantia nigra. Drag to turn, pinch or scroll to zoom, tap any part to name it; .

Lit here: the midbrain, the part that holds the substantia nigra — see it on its own page.

Next to it, each lit on its own page: red nucleus.

Where it is

It is the largest nucleus in the midbrain, lying dorsal to the cerebral peduncles; humans have two, one on each side of the midline. [1]
In brain sections it looks like one continuous band, but it has two parts with very different connections: the pars compacta, which lies medial to (nearer the midline than) the pars reticulata. [1]
The pars reticulata and the internal part of the globus pallidus are separated only by the white matter of the internal capsule; they are so alike that they are sometimes treated as parts of one structure. [1]
Its neighbour in the midbrain tegmentum is the red nucleus; the two are described together as subcortical centres of the extrapyramidal motor system. [3]

What it does

It plays an important role in reward and movement; the cited article lists eye movement, motor planning, reward-seeking and learning among its roles. [1]
The pars compacta supplies the striatum with dopamine through the nigrostriatal pathway. Much of its effect works through the striatum: stimulating the substantia nigra electrically does not by itself produce movement. [1]
The pars reticulata carries the final processed signals of the basal ganglia on to the thalamus and the superior colliculus. Its GABA neurons fire on their own and keep their targets inhibited; a fall in that inhibition goes with movement. [1]
Pars reticulata neurons projecting to the superior colliculus take part in fast (saccadic) eye movements. [1]
The pars compacta is also involved in learned responses to rewards, in spatial learning and in timing: it is active when a person reproduces a time interval. [1]

Connections

The main input to the pars reticulata comes from the striatum by two routes: the direct pathway straight from striatal medium spiny neurons, and the indirect pathway through the external globus pallidus and the subthalamic nucleus. [1]
Pars reticulata outputs use GABA and go to the ventral lateral and ventral anterior nuclei of the thalamus and to the superior colliculus (the nigrothalamic pathway). [1]
The nucleus accumbens also sends it fibres, from its core. [4]

Other names

Latin for “black substance”: parts of it look darker than the tissue around them because its dopamine neurons hold a lot of neuromelanin. [1]
Abbreviated SN; its parts are the pars compacta (SNpc) and pars reticulata (SNpr), and sometimes a pars lateralis, usually counted with the pars reticulata. [1]

Size

The model has no shape for the substantia nigra 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]

Sources

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.