By Dental Tribune International

JENA, Germany: Funded by the German Research Foundation, psychologists from the Friedrich Schiller University Jena in Germany, along with colleagues from Trier University in Germany, have released their initial results on a study looking into what happens to the human brain when hypnotised. Used to help people with a range of issues, such as quitting smoking, improving sleep and even undergoing dental treatment, hypnosis was once thought of as a standard practice in medicine.

“Until the 1920s, hypnosis was a standard part of medical training and it is being used again today in anaesthesia,” said Prof. Wolfgang Miltner, who has been working on the phenomenon for decades.

Sixty participants (split between men and women) took part in the study. They were divided into three groups: individuals who were very suggestible, that is susceptible to hypnosis; individuals of average suggestibility; and those with low suggestibility. “While they were under hypnosis, we had them look at a screen on which we showed them various symbols, such as a circle or a triangle,” said Dr Barbara Schmidt, who conducted the experiment. “The test participants were given the task of counting a particular symbol. At the same time, they were told to imagine that there was a wooden board in front of their eyes. As a result of the suggested obstruction, the number of counting errors rose significantly.”

A comment that typified the experience of highly suggestible participants in particular in undergoing hypnosis was, “I concentrated on the wooden board and saw a board that was similar to the one you showed me in the beginning of the experiment. The board was sometimes more transparent like a cloud, so I could see the stimuli behind, sometimes more solid, so the stimuli were hidden behind it.”

For the researchers to observe brain activity, test participants were connected to an electroencephalograph. “When we look at the neural processes that take place in the brain while processing the symbols, we see that around 400 milliseconds after the presentation of the to-be-counted symbol, there is an extreme reduction in brain activity, although it should normally be very high,” said Schmidt. “However, a short time before this—up to 200 milliseconds after presentation of the stimulus—there are no differences to be seen.”

The practice of hypnotherapy has been used in dentistry for decades. At institutes around the world, dental professionals can learn how to apply hypnosis in their practice, using it to lower dental anxiety and phobia, as well as pain and discomfort for patients. This in turn has been influential in people returning for regular check-ups and cleaning.

With further studies planned, the researchers will be investigating alterations in the processing of acoustic stimuli and pain relief during hypnosis. “We no longer have to show that hypnosis is effective, as that has been proven. The task is now above all to find out why and how such curious changes in perception are possible in people who are hypnotised,” said Miltner.

The study, titled “The power of mind: Blocking visual perception by hypnosis”, was published online on 7 July in the Scientific Reports journal.