Beware of Brains Behind Sleep Paralysis
Imagine waking up in bed, eyes wide open, fully aware of your surroundings—yet you can’t move a muscle. You try to call out but no sound comes. Your chest feels heavy, your breathing shallow. Out of the corner of your eye, a shadowy figure seems to lurk, watching. Panic floods in—until, suddenly, you jolt awake for real.
This chilling experience is known as sleep paralysis, and for centuries, it was explained through folklore—demons sitting on chests, ghostly intruders, or alien abductions. But neuroscience is now uncovering the neurological mechanisms behind these terrifying moments, revealing a complex interplay between REM sleep, brainstem signalling, and emotional processing centres in the brain.
Brainy Matter
Many people believe the body sleeps, but the brain remains awake. Sleep paralysis typically occurs during transitions between rapid eye movement (REM) sleep and wakefulness. REM is the sleep stage most closely associated with vivid dreaming. During this phase, the brain is highly active, but the body is effectively “switched off.”
“During REM sleep, the pons and medulla inhibit motor neurons in the spinal cord, causing muscle paralysis to prevent dream enactment,” explains Dr. Pawan Ojha, Consultant Neurologist and Director of Neurosciences at Medicover Hospitals, Navi Mumbai. “Sleep paralysis occurs when this inhibition persists briefly after waking, so the person becomes conscious before motor control fully returns.”
In essence, the mind wakes up, but the body is still “locked” in the muscle atonia typical of REM. This mismatch between consciousness and physical immobility is what makes the experience so frightening.
Dr. Pankaj Agarwal, Director of Neurology, Stroke and Neurocritical Care at Gleneagles Hospital, Parel, Mumbai, adds, “During REM sleep, the brain activates vivid dreaming while sending inhibitory signals through the brainstem—particularly the pons and medulla—that suppress motor neuron activity. This prevents the body from acting out dreams. Sleep paralysis happens when consciousness returns before these motor pathways fully reactivate.”
Half-Waking State
One of the most disturbing aspects of sleep paralysis is the hallucinations many people experience. Reports of dark figures, a presence in the room, pressure on the chest, or even voices are common across cultures. These visions feel alarmingly real, and neuroscience explains why. “During sleep paralysis, hyperactivity in the amygdala and temporoparietal junction triggers fear and body-awareness distortions, while REM-related visual areas remain active,” says
Dr. Ojha. “Because the brain’s rational frontal regions are still suppressed, these dream-like hallucinations feel vividly real and emotionally intense.”
The amygdala, the brain’s
fear center, remains on high alert. Simultaneously, the temporoparietal junction, which helps us understand our body’s position in space, can misfire, leading to the eerie sensation of a “presence” nearby.
Dr Agarwal further explains: “These vivid hallucinations arise from overactivation of the amygdala, parietal cortex, and temporoparietal junction—regions that process fear, body awareness, and spatial perception. During disrupted REM sleep, dream imagery and emotional centers remain active while rational frontal regions are still suppressed, making these experiences feel intensely real.”
This neurological cocktail explains why so many cultures independently developed myths of supernatural visitations during sleep paralysis episodes.
Underrecognized Phenomenon
Sleep paralysis is more common than many realize. Studies suggest that about 8% of the general population experiences it at least once in their lives, with higher rates among students and individuals with irregular sleep schedules. It can occur as an isolated incident or as part of sleep disorders such as narcolepsy.
Episodes often last only seconds to minutes but leave a lasting impact. People who experience them frequently may develop anticipatory anxiety, fear of bedtime and worsening their sleep quality—a vicious cycle.
The precise reasons why the REM paralysis mechanism sometimes lingers are still being studied. Common contributing factors include sleep deprivation, stress, irregular sleep patterns, and sleeping in the supine position (on the back).
“When sleep is fragmented or disrupted, transitions between sleep stages can become unstable,” notes Dr Ojha. “If the brain wakes up too quickly while the body remains in REM atonia, sleep paralysis can occur.”
Dr Agarwal adds that understanding these mechanisms can help reduce fear. “Recognising that sleep paralysis is a temporary, benign phenomenon caused by a mismatch in brain-body transitions often reassures patients. Good sleep hygiene and stress management can reduce its frequency.”
Understanding Fear
For those who have experienced sleep paralysis, the fear can be overwhelming. But knowing the neurological underpinnings can turn a terrifying experience into one that’s merely strange. Sleep specialists often recommend maintaining regular sleep schedules, avoiding sleep deprivation, and managing stress to reduce episodes.While the shadowy figure in the corner may feel all too real in the moment, neuroscience reveals that it’s a creation of a brain caught between dreaming and waking—a powerful reminder of how intricate, and sometimes glitchy, our sleep systems can be.