How ion channels keep us still during vivid dreams

Today is World Sleep Day, and we thought it’s the perfect occasion to explore some intriguing facts related to sleep and ion channels, especially through the lens of Christopher Nolan’s masterpiece movie “Inception.”

In “Inception,” Dom Cobb (Leonardo DiCaprio’s character) and his team navigate through layers of dreams, engaging in spectacular heists and battles, all while their real physical bodies remain motionless, sedated by the fictional drug Somnacin. Although it’s important to remember that the portrayal of sleep and dreams in “Inception” is largely speculative and artistic, this aspect mirrors a real-life phenomenon: our body’s paralysis during REM (Rapid Eye Movement) sleep.

REM sleep is one of the stages of our sleep cycle where vivid dreams unfold, memories consolidate, and emotional experiences are processed. Remarkably, despite the often intense activity in our dreams, our bodies lie almost entirely still. This phenomenon, known as REM atonia, is nature’s way of preventing us from acting out our dreams, ensuring our safety as we sleep.

But how do our bodies manage to keep us still during such vivid dreams? The answer lies in the brainstem, which sends inhibitory signals to motoneurons in the spinal cord, preventing them from activating muscles. More specifically, during REM sleep, the glutamatergic neurons of the sublaterodorsal nucleus activate inhibitory glycinergic interneurons in the ventral medulla and spinal cord. This leads to the activation of glycine receptors (GlyR) on motoneurons, resulting in their hyperpolarization and silencing. Therefore, during REM sleep, most of the body’s voluntary muscles do not receive activatory signals from motoneurons and stay inactive, even as we scale mountains or flee from danger in our dreams.

When we wake up from REM sleep, the brain rapidly reactivates the neural pathways responsible for muscle tone, allowing for normal movement almost instantly. Nonetheless, occasionally, the transition between sleep and wakefulness doesn’t proceed smoothly, leading to sleep paralysis. This phenomenon occurs when REM atonia persists into wakefulness, leaving one temporarily unable to move or speak. It’s a startling experience, often accompanied by vivid hallucinations, reminiscent of scenarios depicted in “Inception” where characters find themselves trapped between layers of dream and reality.

If you haven’t seen “Inception,” World Sleep Day might be the perfect occasion for you to explore a movie that is considered one of the best of all time by multiple rankings. So, grab some popcorn, settle in, and prepare to enjoy a thrilling narrative that incorporates and creatively expands upon several concepts related to sleep, dreams, and the subconscious mind.