How does neuroscience explain hypnosis

How does hypnosis work neurobiologically?

Questioner: Linus M via the Internet

Published: 08/30/2012

With their help, a completely unique, changed state of consciousness can be evoked: hypnosis. But what actually happens in the brain when you are in a trance?

The answer from the editors is:

Professor Wolfgang H. R. Miltner, holder of the chair for Biological and Clinical Psychology at the Friedrich Schiller University Jena: If we could fully answer this question, brain research would be a long way ahead. The basic problem is: In order to examine hypnosis neuroscientifically, the state of hypnosis must first be clearly defined - and it is not. Some people already speak of a hypnotic state when one can still feel a cut in the skin, but perceives it as less painful; the others only speak of it when you can no longer even feel the cut.

Around a dozen hypotheses are currently being discussed as to how the brain produces hypnosis. Most scientists believe that a process called dissociation is critical. Under hypnosis, the brain no longer seems to bring together various pieces of information from a stimulus into a whole, for example the perception of the intensity and duration or the emotional aspect.

Together with my co-workers, I examined this for switching off pain with hypnosis. The test participants in the control group simply sat quietly and received around 300 painful heat stimuli on one finger one after the other. They were then asked to say how painful the stimulus was and how much reluctance it aroused. The people in the second experimental group were hypnotized; it was suggested to them that their hand was completely numb. In this state they were stimulated with the same stimuli. The test persons in the third group received the same stimuli, but they were not hypnotized, but were distracted: They were supposed to listen to a story to tell it later. The brain waves of all three groups were recorded during the experiment.

That's when we discovered that the nerve cells in the brain had different levels of activity: in the control subjects, the electroencephalogram (EEG) showed a severe rash during irritation. For those who had been distracted by the story, the stimuli were less intense and were also described as less painful. Obviously, the information about the strength of the stimulus did not reach the brain completely. In the case of the hypnotized persons, however, it was found that they had similar EEG curves as the control persons, but experienced the stimuli less painfully, similar to the distracted persons.

In terms of neurobiology, this means that under hypnosis, various associations of nerve cells can no longer communicate with one another. For example, associations of neurons are affected, which distinguish whether the stimulus is perceived as short and pulsating or whether it has been experienced before. The frontal lobe is responsible for this dissociation: Under hypnosis, it seems to switch off communication between different networks that deal with individual stimulus aspects. When the hypnotist finally brings his patient back, the frontal lobe switches on the exchange of information between the individual networks and everything is experienced normally again.

Recorded by Franziska Badenschier