Sensory Deprivation Alters Our Experience, Both of Body and Time

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You have probably heard of sensory deprivation tanks. A number of celebrities swear by them for relaxation, and they have steadily grown in popularity over the past few decades. They work by minimizing sensory inputs from the external world: The tank is filled with high salinity water that allows the user to float freely on the surface; the water is body temperature; earplugs are worn to reduce sound; and the tank is usually situated in a dark room or enclosed space.

The potential therapeutic benefits of these tanks have been studied by psychologists and neuroscientists for the past few years, and new research has highlighted how they alter our experience and reduce our stress.

“Subjects felt significantly more relaxed, less anxious, and less tired,” states a Scientific Reports study about the therapeutic use of these tanks, after a single session of use. “The subjective experience of arousal, anxiety, tension, and stress significantly decreased.”

Float Tank Therapy

Referring to these tanks as ‘float tanks’ rather than ‘sensory deprivation tanks,’ and referencing their therapeutic use as ‘flotation-REST’ (Reduced Environmental Stimulation Therapy), researchers have their own terminology for floating experiences.

There are a couple reasons for this. First, while these experiences reduce sensory inputs from outside the body, they increase users’ sensitivity to sensory inputs from inside the body, interpreted through the process of interoception, including heart beat and breathing rate. Thus, to label these experiences as ‘sensory deprivation’ isn’t quite right. Second, ‘sensory deprivation’ carries negative connotations, where the user is deprived of something without acquiring something new in return.

In the Scientific Reports study, published in April 2024, researchers wanted to test how a session of floatation-REST would affect participants’ subjective experience of the body boundary (the perceived border of their physical being), as well as the passage of time, when compared to bed-REST (a control condition that entailed lying down on a warm waterbed in a dark and quiet room). Researchers were also interested in the relationship between these subjective experiences and stress.

Specifically, researchers suspected that flotation-REST would induce an altered state of consciousness (ASC) in the individuals who experienced it.

“Across different induction techniques, either psychological, such as in meditation, or pharmacological, such as when using drugs, … altered state[s] of consciousness … are often reported afterwards to consist of a distortion of the senses of time and bodily self, in peak states culminating as ‘timelessness’ and ‘selflessness,’” says neuroscientist Marc Wittmann, one of the study authors and a fellow at the Institute for Frontier Areas of Psychology and Mental Health in Freiburg, Germany.

Read More: Psychedelics Could Be the Future of Psychotherapy

How Flotation Rest Therapy Works

According to Wittmann, free floating is a type of instant meditation, since individuals without prior experience in meditation can usually access altered states where they feel a shift in the boundaries of their bodies and a distortion in their sense of time. In the study, a 60-minute session in a flotation device induced these ASCs in participants, as measured through a questionnaire assessing their experiences after their time in the tank.

In contrast to the flotation-REST condition, participants who were assigned to the bed-REST condition didn’t feel the same alterations in their subjective experience of body boundary and time. The immersion in water heated to skin temperature and saturated with salt in flotation-REST constituted the biggest difference between the two conditions. The other difference was air temperature. This was also matched to skin temperature in the flotation-REST condition, while it remained at room temperature in the bed-REST condition.

“Thus, during floatation-REST, the close matching of the ambient temperatures to that of the skin appears to blur the boundaries between air, body, and water. This blurring of boundaries leads to an ASC where one can no longer discern where their body begins and ends, the essence of body dissolution,” the researchers wrote in their study.

Wittmann suspects that the altered awareness of bodily signals during flotation-REST affected the participants’ experience of time.

Prior fMRI research has shown that the insular cortex, the brain structure for processing bodily signals … is the most important structure for sensing time,” Wittmann says, activating whenever we assess the duration of a specific stimulus.

Read More: Do Psychedelic Drug Therapies Actually Require Getting High?

Floating From Stress

According to the Scientific Reports study, participants in the flotation-REST condition also experienced a stronger reduction in stress compared to the bed-REST condition. Researchers believe that the ASCs associated with the flotation-REST helped to mediate those feelings. A stronger bodily sensation is associated with stronger anxiety, Wittmann says, thanks to the stress reaction of the body, meaning that flotation-REST leaves us with less bodily sensation and less anxiety.

Other studies have also pointed to the potential therapeutic benefits of flotation-REST, including reduced stress, muscle tension, pain, and depression. What’s more, these studies have also found that floatation-REST has the highest positive effect for individuals who suffered from the highest levels of anxiety.

Thus, as more and more research reveals the benefits of sensory deprivation, this new study reveals the potential mechanisms behind those benefits, namely the alteration of our sense of self and time. Taken together, this work supports a safe, non-pharmacological approach for relieving stress-related symptoms — sending them away, simply by floating.

Read More: Grappling With the Science of Touch-Based Healing Practices

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Conor Feehly is New Zealand-based science writer who covers a wide range of topics, including astronomy and neuroscience, with an eye for research at the intersection of science and philosophy. He received a masters in science communication degree from the University of Otago. Conor is a regular contributor to Discover Magazine, with his work also appearing in New Scientist, Nautilus Magazine, Live Science, and New Humanist among others.

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