Nucleus · one in each half of the brain

Thalamus

The brain's grand central station: nearly every sense stops here on its way up.

Open in 3D

The thalamus is a pair of egg-shaped masses sitting right in the middle of the brain. Almost every message from your senses except smell (sight, hearing, touch and taste) passes through it before reaching the cortex, where you become aware of it. But it is more than a relay. It filters what gets through, helps set how alert you are, and keeps the cortex in constant conversation, which is why it is so tied to sleep and consciousness.

Where it is

Dead center of the brain, one on each side of the thin third ventricle, sitting on top of the brainstem.

What it does

Think of it as a hotel receptionist who takes every incoming call, decides which ones matter, and puts them through to the right room.

Inside the thalamus

• Anterior nucleusA memory relay on the famous Papez loop that also helps you find your way.
• Mediodorsal nucleusThe prefrontal cortex's close partner, linking thinking and planning with feelings.
• Ventral anterior nucleusA motor relay that carries the basal ganglia's "go" decisions back to the cortex.
• Ventral lateral nucleusWhere the cerebellum's timing and the basal ganglia's choices meet on the way to motion.
• Ventral posterior nucleusThe body's touch and pain relay, passing every tap, ache and taste to the cortex.
• Lateral posterior nucleusA neighbor of the pulvinar that links what you see to where things are.
• PulvinarThe thalamus's big back cushion, a spotlight that helps pick what you look at.
• Lateral geniculate nucleusVision's relay station: a six-layered bent knee where signals from your eyes arrive.
• Medial geniculate nucleusThe hearing relay: the sounds you hear pass through this little bent knee.
• Midline & intralaminar nucleiThe thalamus's wake-up crew, helping switch on alertness and attention.

Works with

• Primary somatosensory cortexReceives the touch, pain and temperature signals it relays from the body.
• Primary visual cortexReceives the signals from your eyes after they pass through the thalamus.
• Motor stripGets movement signals from it that come from the basal ganglia and cerebellum.
• Basal gangliaKeep parts of it under a brake and release it when an action is chosen.
• CerebellumSends it timing and coordination signals for smooth movement.
• Relay neuronIts main kind of nerve cell, built to pass messages on to the cortex.

When it goes wrong

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

Surprising facts

• Smell is the only sense that does not stop at the thalamus first. It goes straight to the smell areas of the cortex.
• In many people, the left and right thalamus touch in the middle through a small bridge of tissue, but some people have no bridge at all.
• The cortex also sends many fibers back down to the thalamus, forming constant two-way loops.

Where the name comes from

From Greek "thalamos", meaning "inner chamber" or "bedroom", fitting for a structure tucked in the brain's very center.

Learn it in a lesson

• The thalamusThe brain's relay station. A short guided lesson in 3D.

Sources

1. Neuroanatomy, Thalamus, StatPearls, NCBI Bookshelf
2. 13.2 The Central Nervous System, OpenStax, Anatomy and Physiology 2e
3. Interthalamic adhesion, Radiopaedia

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