How can man enjoy the emptiness of silence

Silence: Why the brain needs rest

As neurologists found, in such a situation the auditory cortex remains active, as if the song had never stopped. The memory creates imaginary sounds which, as catchy tunes, are sometimes as annoying as a single CD in an endless loop.

Without external input, the brain produces its own film. At the end of the 1990s, the neurologist Marcus Raichle from Washington University in St. Louis and his team discovered the origin of our mental cinema: the so-called Default Mode Network or the idle state network. This group of brain regions becomes active whenever we do nothing and let our thoughts wander. As soon as we turn back to a task, the nerve cells involved fall silent. They are located in areas of the prefrontal cortex, in the posterior cingulate cortex, in the middle temporal lobe and in the upper part of the parietal lobe (see graphic "What the brain does when we do nothing").

What many consider to be a waste of time or a lack of concentration (which dreamy child doesn't have to listen to regularly that they should finally concentrate?) Is actually an important gift of the brain. Letting your thoughts run free every now and then, for example, encourages ingenuity. Those who daydream regularly should also be cognitively more flexible and be able to solve problems more easily.

New ideas through mental idleness

Psychologists differentiate between two types of daydreaming: In addition to the involuntary, spontaneous wandering of thoughts, there is another form in which we consciously choose to go mentally idle. Scientists from the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig discovered in 2016 that this type of mental drifting goes hand in hand with certain changes in the brain. "In people who often deliberately indulge their thoughts, the cortex is thicker in areas of the frontal lobe," explains Johannes Golchert, doctoral student at the Leipzig Institute and first author of the study. This region is particularly important for the control of one's own actions.

According to the Attention Restoration Theory of environmental psychologists Rachel and Stephen Kaplan, the brain can regenerate its cognitive resources better if it receives as little sensory input as possible. If we are permanently exposed to many different stimuli, our ability to concentrate will be exhausted at some point. We are no longer able to focus our thoughts for long periods of time; the batteries are empty and can only be recharged in a low-stimulus environment. According to the psychologists, this works best in nature: watching a sunset, counting stars in the sky or breathing fresh forest air - all of this should make the brain efficient again.

It is still unclear how scientifically sound this theory is. According to more recent meta-analyzes, time out in the country improves certain memory functions, at least in the short term, and strengthens visual awareness.

In nature, however, it is seldom completely quiet. Researchers are using so-called floating tanks to study how the body reacts when there is a brief lack of sensory stimuli. These are tubs with concentrated salt water that either have a soundproof and lightproof hood or are located in a comparable isolated room. Isolated from the outside world, the test subjects float weightlessly on the water. Due to the high salt content, they cannot perish (see »Time out for the senses«).

In 2005, Dutch psychologists came to the conclusion that the floating technique (also called REST, for restricted environmental stimulation technique) alleviates typical stress symptoms: It lowers cortisol and adrenaline levels as well as blood pressure and increases general well-being. The method is said to be even more effective than classic relaxation techniques such as progressive muscle relaxation and autogenic training.

In addition, the stimulus withdrawal in the tub apparently helps people with various anxiety disorders, as Justin Feinstein from the Laureate Institute for Brain Research in Tulsa and his colleagues found out in 2018. The neuropsychologists placed 50 patients with generalized anxiety disorder, panic disorder, agoraphobia, social anxiety, or post-traumatic stress disorder in a floating tank for one hour. Immediately before and after the bath, the participants provided information about their current state of health by means of a questionnaire.

Feelings of happiness in the bathtub

Regardless of the form of the anxiety disorder, sensory deprivation produced a sense of relaxation. The test subjects then felt less stress, were less anxious and perceived pain less. At the same time, their mood rose: they became more relaxed and generally happier. The more they had previously suffered from their fear, the greater the effect. It was significantly weaker in healthy control subjects.

Alone in a water-filled chamber, just hearing your own breath and the beating of your heart - the very thought of it can be frightening. With floating therapy, however, the patients can speak to the study directors via a loudspeaker system and switch on the light independently. That calms you down tremendously; also the feeling of being able to break off the session at any time.

Without this security, however, the withdrawal of stimuli can become torture. It is even a dreaded torture method that was already used in the Middle Ages in the form of solitary confinement or in a so-called camera silens, a "silent room". After a short time, the prisoners begin to hallucinate, and various body functions such as sleep-wake rhythm and digestion get mixed up.

Every now and then we all experience significantly less drastic situations in which there is only a few minutes of silence. And they too can be uncomfortable. For example, when we meet up with an old school friend in a café after years and the conversation just doesn't want to get going. How oppressive just a few seconds of silence can be here! We quickly take refuge in alternative actions: we rummage in our pockets, twirl our hair or say something irrelevant.

But why can we endure silence so badly, whether together or alone? According to Michel Le Van Quyen from the Institut national de la santé et de la recherche médicale (Inserm) in Paris, humans have a natural desire for those stimuli that are necessary for the development of the brain. This also includes the voice of other people. "The silence represents a void that makes some people worry about loneliness," says the neuroscientist. Maybe it's also a matter of habit. Those who have never learned to endure silence will be even more burdened later.

So we would do well to give ourselves and our children regular short acoustic breaks. How about right now, for example? You have come to the end of the article: Switch off the hood and radio and ... enjoy!