What happens in your brain when you go into a coma?

Updated

Coma stems from severe dysfunction in the brainstem's arousal system and the thalamus's relay role, while the claustrum's integration may also be impaired, leaving the cortex without the input needed for wakefulness or awareness.

Brainstem, Thalamus, Claustrum lit up on the Brain Atlas 3D brain: what happens in your brain when you go into a coma
Figure. The brain regions that light up when you go into a coma, in order: Brainstem (arousal failure), then Thalamus (relay shutdown), then Claustrum (consciousness off).

Watch it light up on the 3D brain

Brain regions that light up

OrderRegionWhat it does here
1BrainstemThe brainstem's reticular activating system stops sending wake-up signals.
2ThalamusThe thalamus, which normally routes sensory information to the cortex, goes quiet.
3ClaustrumThe claustrum, thought to bind information into experience, may become inactive.

1. Brainstem: arousal failure

Step 1 of what happens in your brain when you go into a coma: Brainstem lit on the Brain Atlas 3D brain
Figure 1. Brainstem, arousal failure: The brainstem's reticular activating system stops sending wake-up signals.

The brainstem houses the reticular activating system, which maintains cortical arousal. In coma, damage or metabolic failure here silences this system, so the brain cannot transition to a wakeful state.

2. Thalamus: relay shutdown

Step 2 of what happens in your brain when you go into a coma: Brainstem, Thalamus lit on the Brain Atlas 3D brain
Figure 2. Thalamus, relay shutdown: The thalamus, which normally routes sensory information to the cortex, goes quiet.

The thalamus is the gateway for sensory input to the cerebral cortex. Without brainstem activation, its neurons hyperpolarize and stop relaying signals, preventing conscious perception.

3. Claustrum: consciousness off

Step 3 of what happens in your brain when you go into a coma: Brainstem, Thalamus, Claustrum lit on the Brain Atlas 3D brain
Figure 3. Claustrum, consciousness off: The claustrum, thought to bind information into experience, may become inactive.

The claustrum is a thin sheet with connections to many cortical areas. Its activity correlates with conscious awareness, and its dysfunction may break the integration needed for a unified experience.

Good to know

  • Coma is defined as a state of unarousable unresponsiveness lasting more than one hour.
  • The brainstem's reticular formation is essential for wakefulness; small lesions there can cause coma.
  • Metabolic disturbances like hypoglycemia or drug overdose can cause coma by impairing neuronal function diffusely.

Coma vs Vegetative State

In coma, the eyes are closed and there is no sleep-wake cycle. In a vegetative state, the brainstem may recover enough to open eyes and have sleep-wake cycles, but awareness remains absent because cortical function is severely impaired.

Test yourself

  1. Which brain region is the primary source of wakefulness signals that fail in coma?

  2. The thalamus contributes to coma by:

  3. What is a key difference between coma and vegetative state?

0 of 3 answered · 0 correct

Simplified: many regions work together at once, and this shows the main players in the order they act. For learning only, not medical advice.