What happens in your brain when you have sleep paralysis?

Updated

During sleep paralysis, the brainstem maintains REM atonia, causing paralysis, while the amygdala overreacts to perceived threats and the prefrontal cortex may be underactive, impairing rational thought. Visual hallucinations may arise from spontaneous occipital activity.

Brainstem, Prefrontal Cortex, Amygdala, Occipital Cortex lit up on the Brain Atlas 3D brain: what happens in your brain when you have sleep paralysis
Figure. The brain regions that light up when you have sleep paralysis, in order: Brainstem (paralysis persists), then Prefrontal Cortex (reality check fails), then Amygdala (fear surges), then Occipital Cortex (visions appear).

Watch it light up on the 3D brain

Brain regions that light up

OrderRegionWhat it does here
1BrainstemThe brainstem continues sending atonia signals to the spinal cord, paralyzing voluntary muscles.
2Prefrontal CortexThe prefrontal cortex may be underactive, impairing executive function and self-awareness.
3AmygdalaThe amygdala becomes highly active, generating intense fear and a sense of threat.
4Occipital CortexThe occipital cortex may produce vivid, dream-like visual hallucinations.

1. Brainstem: paralysis persists

Step 1 of what happens in your brain when you have sleep paralysis: Brainstem lit on the Brain Atlas 3D brain
Figure 1. Brainstem, paralysis persists: The brainstem continues sending atonia signals to the spinal cord, paralyzing voluntary muscles.

Normally, REM sleep suppresses motor neurons to prevent acting out dreams. During sleep paralysis, this atonia persists even as the cortex wakes, leaving the person unable to move or speak.

2. Prefrontal Cortex: reality check fails

Step 2 of what happens in your brain when you have sleep paralysis: Brainstem, Prefrontal Cortex lit on the Brain Atlas 3D brain
Figure 2. Prefrontal Cortex, reality check fails: The prefrontal cortex may be underactive, impairing executive function and self-awareness.

Reduced activity in the prefrontal cortex may mean the person cannot rationally evaluate the experience, so hallucinations and paralysis feel terrifyingly real. This region would normally help override fear.

3. Amygdala: fear surges

Step 3 of what happens in your brain when you have sleep paralysis: Brainstem, Prefrontal Cortex, Amygdala lit on the Brain Atlas 3D brain
Figure 3. Amygdala, fear surges: The amygdala becomes highly active, generating intense fear and a sense of threat.

The amygdala is the brain's alarm system, and during sleep paralysis it is thought to be overactive, creating the feeling of a menacing presence or impending doom.

4. Occipital Cortex: visions appear

Step 4 of what happens in your brain when you have sleep paralysis: Brainstem, Prefrontal Cortex, Amygdala, Occipital Cortex lit on the Brain Atlas 3D brain
Figure 4. Occipital Cortex, visions appear: The occipital cortex may produce vivid, dream-like visual hallucinations.

Without normal sensory input, the occipital cortex may fire spontaneously, generating images such as shadowy figures or intruders. These hallucinations are often consistent with the fear response.

Good to know

  • Sleep paralysis occurs during transitions between REM sleep and wakefulness, and studies suggest up to 8% of the general population experiences it.
  • The experience is often accompanied by hypnagogic or hypnopompic hallucinations, which are vivid dream-like perceptions.
  • Sleep paralysis is more common in people with narcolepsy, but can occur in healthy individuals, especially when sleep-deprived.

Sleep Paralysis vs REM Sleep Behavior Disorder

In sleep paralysis, REM atonia persists into wakefulness, causing paralysis with conscious awareness. In REM sleep behavior disorder, the atonia fails during REM sleep, so people act out their dreams physically. Both involve brainstem dysfunction, but with opposite effects on muscle tone.

Test yourself

  1. Which brain region is primarily responsible for the muscle paralysis in sleep paralysis?

  2. The underactivity of which region contributes to the feeling that hallucinations are real?

  3. What role does the amygdala play in sleep paralysis?

0 of 3 answered · 0 correct

Simplified: many regions work together at once, and this shows the main players in the order they act.