Nucleus · one in each half of the brain
Substantia nigra pars reticulata
Also called SNr
A gatekeeper that keeps movements and glances on hold until the right moment.
The pars reticulata is the paler, loosely packed part of the substantia nigra. Its cells use GABA, a calming "hush" messenger, to keep a brake on the thalamus and on eye-movement centers. When the basal ganglia choose an action, it briefly lifts the brake so that action can go. It is one of the two main exits of the basal ganglia.
Where it is
The paler layer of the substantia nigra in the midbrain, lying next to the dark pars compacta and the big fiber bundles coming down from the cortex.
What it does
Holding the brake
It keeps unwanted actions switched off by holding back the thalamus.
Releasing the brake
When the striatum picks an action, it briefly quiets this area, letting that action start.
Guarding glances
It controls the superior colliculus, deciding when your eyes may jump to a new target.
Passing the verdict
Along with the internal globus pallidus, it delivers the basal ganglia's final "go" or "no go" to the thalamus.
Think of it as a hand holding a door shut: it lets go for a split second only when the right movement is ready to walk through.
Works with
- Superior colliculusIt sends braking signals to this eye-aiming center and lifts them to allow a glance.
- Internal globus pallidus (GPi)This is its twin exit, doing the same braking job mainly for body movements.
- ThalamusIts brake signals reach the thalamus, which relays movement plans to the cortex.
- Caudate nucleusThe caudate sends it signals that can quiet it, releasing the brake.
- Subthalamic nucleusThis small nucleus pushes it to brake harder when you need to stop.
- GABAIts cells use GABA, the brain's main calming messenger.
When it goes wrong
Parkinson's disease
When dopamine runs low, this gate tends to clamp down too hard, which is thought to be one reason movements feel so hard to start.
For learning only, not medical advice. If you have a health concern, talk to a doctor.
Where the name comes from
Latin for "net-like part". Its cells are more loosely scattered than in the compact part, like knots in a net.
Quick quiz
3 questions. Your answers are saved and come back in your daily review.
Which of these is a job of the pars reticulata?
Show the answer
Holding the brake. It keeps unwanted actions switched off by holding back the thalamus.
Holding the brake. It keeps unwanted actions switched off by holding back the thalamus.
The pars reticulata is part of which larger structure?
Show the answer
Substantia nigra. It belongs to the substantia nigra.
Substantia nigra. It belongs to the substantia nigra.
Which part fits this description? "Like a hand holding a door shut: it lets go for a split second only when the right movement is ready to walk through."
Show the answer
Pars reticulata. It is the pars reticulata. A gatekeeper that keeps movements and glances on hold until the right moment.
Pars reticulata. It is the pars reticulata. A gatekeeper that keeps movements and glances on hold until the right moment.
These parts now come back in your daily review, just before you would forget them.
Practice it and its neighbors in 3DSources
- Neuroanatomy, Substantia Nigra, StatPearls, NCBI Bookshelf
- Neuroanatomy, Basal Ganglia, StatPearls, NCBI Bookshelf
- Neuroanatomy, Mesencephalon Midbrain, StatPearls, NCBI Bookshelf
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