What happens to the brain when deprived of all external sensory input?

When Dr. John C Lilly studied this back in the 1950s, he thought that all activity in the brain would stop, and, along with it, consciousness too. He would become less human and more ape man.

It turns out he was wrong.

Staying upright in a primitive box-like tank full of water with only a face mask to breathe through, might seem crazy if not distressing. But once inside, Dr Lilly found that he had never been this relaxed in his entire life before. What should have been an experiment turned into a revolutionary tool with which to achieve deeper states of awareness.
He made a few adjustments to the tank and named it sensory deprivation floating therapy.

The scientists of the day weren’t so convinced. ‘Sensory deprivation’ came too close to ‘solitary confinement’ for them. It must be a torture device, if not a one-way ticket to an asylum.

  The idea caught on, though and, as more scientists tested it out, they became convinced of its positive effects. They decided to rename it REST or restrictive environmental stimulation, a term that accurately describes the experience most people have in the tank these days.

Today, when you go for a float in any of the major centres of the world, the features have been somewhat improved. The now pod-like dome resembles a soundproof spaceship with a roof that you have complete control over. Inside, you drift naked in a mere 30 centimeters of water in which 500kg of Epsom salt has been dissolved. For 45 minutes to an hour, you can lie back, relax and spend time with yourself while being surrounded by stillness and darkness.

What’s so good about that?


Thanks to the high concentration of salt in the water, there is no need to hold yourself up. Without any gravity to pin you down, all your muscles, ligaments and bones get a chance to relax and let go.

  This relieves the body temporarily of any aches and pains it may be carrying from sitting still or standing for most parts of the day. Floating releases the pressure in the back, hips, shoulders and spine.

  By relaxing the spine, the nervous system gets a break too. Your sympathetic nervous system is located around your spinal cord which connects to all the other organs in your body.

  This slows your heartbeat down, releasing more oxygen into your bloodstream and you start to breathe more deeply, which calms you down more.


Epsom salt dissolves into magnesium, something every cell in the body needs.

  The daily recommended intake is between 300-400 mg depending on size and weight. The fewer nutrients in our diets, the more stress, caffeine and overstimulation will cause a deficit of this essential mineral.

  Not only does it play a vital role in more than 300 biological functions, but it is an important co-factor in many enzymic reactions too.

 It breaks our food down, turning it into the energy we live on every day. It stops the muscles from cramping by moving blood sugar to break down lactate. It also keeps bones healthy.

  It acts as a natural antidepressant. By assisting with the regulation of the nervous system, it combats the damage cortisol does to the body, releasing a good dose of endorphins – the body’s painkillers.

  By absorbing half a ton of this good stuff through the pores of your skin, all your resources get replenished.


Melatonin is our natural anesthesia. Without it, we don’t get the rest we need.

  When it becomes dark, melatonin gets released letting the body know it’s time for bed. It keeps us asleep for the full duration of the night. By morning light, melatonin production becomes less, waking us up.
In the mad rush of our demanding lives, this natural circadian rhytm gets disrupted. Instead of listening to the cues inside, we become ruled by the watch on our arm.

  Our bodies grow tired and the mind has trouble switching off, overwrought. This leads to insomnia and, in some cases, depression. 

  While floating in the tank, time stands still. This helps restore balance to the internal clock. One hour in the pod is as good as getting three hours of proper sleep.


Everything we know about the world, we know through our senses. Our eyes, ears, taste buds and even skin provides us with information 24/7.

  Our bodies react to this information. Whether it is by shivering when the temperature drops, or jumping with fright at a sudden loud noise.

  The amygdala, the part of the brain that keeps us safe, is constantly on the lookout for possible dangers. Inside the pod, you’re safe. Safer even than the house you live in.

  With a good pair of waterproof plugs in your ears, you don’t have to listen to anything besides your heartbeat. At 35.5 degrees, the water is exactly skin temperature and envelops you like a cacoon.

  There are no big screens, gadgets, lights, or phones to distract you. After a while, your mind gets bored and is forced to look for a new source of entertainment.

  By tuning out the world, you tune into yourself and the data that lies within.

 Theta wave state

Unlike a device or a computer screen, the brain doesn’t turn off. It remains active until your very last breath.

  While sleeping, we produce delta waves, a very low frequency of electric activity between neurons. In the morning before opening our eyes, we produce alpha waves.

  In between these two, are theta waves. It’s said that only holy men who have practised meditation regularly for many years have managed to reach and sustain it without drifting off to sleep.

  Creatives and artists have attributed their masterpieces to this lucid dream-like state. The great minds of our time have also used it to solve some of the world’s biggest problems.

  Unrestricted by the ego or conscious mind, the subconscious expresses itself through a free flow of ideas, insights or memories from childhood.

  Instead of seeing your life flash before your eyes, you see it clearly now in slow motion.

 The result of these factors combined is that you come out feeling relaxed, recharged, your senses wide awake and with a whole new perspective. No practitioner or therapist required. It would seem that under such perfect conditions, depriving yourself of all sound, sight and other stimuli can be healthy for you.

  Whatever you’re looking for, you’ll find it here. For most, it’s a greater connection with themselves and life itself. For others, it’s like coming home again.

Floating sessions are avaiable for bookimgs online:
with Float Zero, Neuro Float, Float Studio at Seven Circles, or Radi8 Float

Vilien-Mimi Coertzee

Vilien-Miri Coetzee is a wellness writer specialising in mental health and nervous system regulation. She is passionate about exploring the various modalities we use to heal ourselves naturally. Since her first float in Bali three years ago, floating has helped her build resilience in the face of life’s many challenges. Instagram: @viliencoetzee Blog: Lifeseekers.co.za

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