Nucleus · one in each half of the brain

Substantia nigra

Also called SN, Black substance

The "black substance": dark dopamine cells whose loss causes Parkinson's disease.

The substantia nigra lit up in a 3D model of the human brain

The substantia nigra is a pair of curved, dark bands deep in the midbrain. It is dark because many of its cells are full of neuromelanin, a black pigment that builds up as a by-product of making dopamine. Its dopamine helps the basal ganglia start movements smoothly and easily. When these cells die, Parkinson's disease appears.

Where it is

Deep in the midbrain, one on each side, just behind the thick bundles of fibers that carry commands down from the cortex.

What it does

Fuel for movement

Dopamine from here lets the basal ganglia pick out and launch the movements you want.

A movement gate

Its other half acts as a gate that holds unwanted movements back until the right moment.

Eye movements

It helps decide when your eyes may jump to look at something new.

Learning habits

Its dopamine signals help turn repeated actions into smooth, automatic habits.

Think of it as the fuel pump for your movement system: when it stops supplying dopamine, the engine sputters and stalls.

Inside the substantia nigra

Pars compactaTightly packed dopamine cells that power smooth movement, lost in Parkinson's.
Pars reticulataA gatekeeper that keeps movements and glances on hold until the right moment.

Works with

PutamenDopamine flows from here to the putamen, where body movements are selected.
Caudate nucleusIt also supplies dopamine to the caudate nucleus, the putamen's partner in the striatum.
Internal globus pallidus (GPi)Its paler half is a twin of this basal ganglia exit, sharing the job of braking movement.
Subthalamic nucleusThis small nucleus drives its braking half, and it is a common target for Parkinson's treatment.
Superior colliculusIt controls when this eye center in the midbrain is allowed to launch a quick glance.
DopamineIt is one of the brain's main dopamine factories.

When it goes wrong

Parkinson's disease

When its dopamine cells die, people develop a shaking hand at rest, stiff muscles, slow movements and a shuffling walk. Many of these cells are already gone before symptoms start.

Faded color

In people who had Parkinson's, the substantia nigra looks pale instead of black, because the pigmented cells have been lost.

For learning only, not medical advice. If you have a health concern, talk to a doctor.

Surprising facts

Its dark pigment also traps iron, and the rusting of that iron may help explain why these dopamine cells are so easily damaged.

Where the name comes from

Latin for "black substance". It is one of the few parts of the brain you can spot by its color alone in a sliced brain.

Learn it in a lesson

The basal gangliaChoosing which movement goes. A short guided lesson in 3D.

Quick quiz

3 questions. Your answers are saved and come back in your daily review.

Which of these is a job of the substantia nigra?
Show the answer
Fuel for movement. Dopamine from here lets the basal ganglia pick out and launch the movements you want.
The substantia nigra is part of which larger structure?
Show the answer
Midbrain. It belongs to the midbrain.
Which part fits this description? "Like the fuel pump for your movement system: when it stops supplying dopamine, the engine sputters and stalls."
Show the answer
Substantia nigra. It is the substantia nigra. The "black substance": dark dopamine cells whose loss causes Parkinson's disease.

Sources

Neuroanatomy, Substantia Nigra, StatPearls, NCBI Bookshelf
Parkinson Disease, StatPearls, NCBI Bookshelf
3.2 Neurotransmitters Made from Amino Acids, OpenStax, Introduction to Behavioral Neuroscience

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