01-14-2008, 02:02 PM
Telegraph.co.uk
"You will not remember this" seems to work, says Roger Highfield
When hypnosis is used to make people forget, it produces measurable changes in the brain that suggest the effects are real and not simply people "letting themselves go."
About two thirds of the population can be hypnotised and common uses include the treatment of pain, anxiety and phobias.
The study found that parts of the brain were affected by hypnosis However, sceptics have argued that hypnosis does not result in an altered state of consciousness - a "trance" - but is an exaggerated form of social compliance, where subjects suspend their critical faculties to do whatever a hypnotist asks of them.
Now brain scans of people that are taken following a hypnotic suggestion to forget have revealed parts of the brain really are affected.
The Israeli team that did the study say their insights into memory suppression and recall may help understand the mechanisms underlying some forms of amnesia, along with how we suppress distressing memories or things we would rather not dwell upon.
Prof Yadin Dudai and colleagues at The Weizmann Institute of Science, Rehovot, describe in the journal Neuron a study on two groups of volunteers - those who were susceptible to hypnotic suggestions and those who were not - after they had shown a documentary depicting a day in the life of a young woman.
A week later, they placed them in a brain scanner and induced them into a hypnotic state. In this state, the scientists gave the subjects a posthypnotic suggestion to forget the movie, also giving them a reversibility cue that would restore the memory.
Once the subjects had been brought out of the hypnotic state, the researchers tested their recall, then gave them the reversibility cue and tested their recall again. As expected, the hypnosis-susceptible group showed reduced recall of the movie, compared with the hypnosis-non-susceptible group.
Analysis of the brain scans revealed distinctive differences between the hypnosis-susceptible group and -non-susceptible group in specific brain areas - occipital, temporal, and prefrontal areas.
"The surprise for us was that activity was raised during memory suppression in one specific region in the frontal cortex." In effect, it probably tells the other brain regions "don't even think about retrieving that memory" he says.
"The one thing we can say for sure is that hypnotism worked under the conditions we used," says Prof Dudai, adding that the findings are different from those seen in people who attempt to deceive. "We are therefore highly confident that this is not an artifact."
Coauthor Avi Mendelsohn adds that further studies will be needed to determine whether their findings give insights into how the brain stores memory and apply to cases of amnesia seen by doctors.
The team is cautious about extrapolating from their finds to other use of hypnotism.
http://www.telegraph.co.uk/earth/main.jhtml;jsessionid=HCFS1NLJ5T3T1QFIQMFSFF4AVCBQ0IV0?view=DETAILS&grid=A1YourView&xml=/earth/2008/01/11/scihypno111.xml
"You will not remember this" seems to work, says Roger Highfield
When hypnosis is used to make people forget, it produces measurable changes in the brain that suggest the effects are real and not simply people "letting themselves go."
About two thirds of the population can be hypnotised and common uses include the treatment of pain, anxiety and phobias.
The study found that parts of the brain were affected by hypnosis However, sceptics have argued that hypnosis does not result in an altered state of consciousness - a "trance" - but is an exaggerated form of social compliance, where subjects suspend their critical faculties to do whatever a hypnotist asks of them.
Now brain scans of people that are taken following a hypnotic suggestion to forget have revealed parts of the brain really are affected.
The Israeli team that did the study say their insights into memory suppression and recall may help understand the mechanisms underlying some forms of amnesia, along with how we suppress distressing memories or things we would rather not dwell upon.
Prof Yadin Dudai and colleagues at The Weizmann Institute of Science, Rehovot, describe in the journal Neuron a study on two groups of volunteers - those who were susceptible to hypnotic suggestions and those who were not - after they had shown a documentary depicting a day in the life of a young woman.
A week later, they placed them in a brain scanner and induced them into a hypnotic state. In this state, the scientists gave the subjects a posthypnotic suggestion to forget the movie, also giving them a reversibility cue that would restore the memory.
Once the subjects had been brought out of the hypnotic state, the researchers tested their recall, then gave them the reversibility cue and tested their recall again. As expected, the hypnosis-susceptible group showed reduced recall of the movie, compared with the hypnosis-non-susceptible group.
Analysis of the brain scans revealed distinctive differences between the hypnosis-susceptible group and -non-susceptible group in specific brain areas - occipital, temporal, and prefrontal areas.
"The surprise for us was that activity was raised during memory suppression in one specific region in the frontal cortex." In effect, it probably tells the other brain regions "don't even think about retrieving that memory" he says.
"The one thing we can say for sure is that hypnotism worked under the conditions we used," says Prof Dudai, adding that the findings are different from those seen in people who attempt to deceive. "We are therefore highly confident that this is not an artifact."
Coauthor Avi Mendelsohn adds that further studies will be needed to determine whether their findings give insights into how the brain stores memory and apply to cases of amnesia seen by doctors.
The team is cautious about extrapolating from their finds to other use of hypnotism.
http://www.telegraph.co.uk/earth/main.jhtml;jsessionid=HCFS1NLJ5T3T1QFIQMFSFF4AVCBQ0IV0?view=DETAILS&grid=A1YourView&xml=/earth/2008/01/11/scihypno111.xml
