Over and over, we hear the question, what is hypnosis and what is the science in it? A brain signature of being hypnotized was first recognized in 2012 with functional MRI (fMRI), a type of MRI that showed brain . Regions of the brain connected with executive control and attention were demonstrated to be involved.
In particular, hypnotized subjects exhibited stronger co-activation between components of the executive-control network (manages basic cognitive functions) and the salience network (decides which stimuli should receive attention). Both networks in the brain are activated in unison. In those who were not under hypnosis, this connectivity was not observed.
What elevated these experiments to a higher league is the fact that researchers used fMRI to detect the parts of brain that responded when subjects analyzed colors. The color areas in both left and right hemispheres reacted when the subjects were told to look at colors. The researchers confirmed that hypnosis is indeed a distinct psychological state and undoubtedly not a result of playing a role.
Another exciting observation from these trials were the hemispheric variances between the hypnotized and non-hypnotized brain. When non-hypnotized subjects were requested to point out colors from a black-and-white picture, only the right hemisphere was activated. The left hemisphere, where reason and logic is processed, responded only during hypnosis.
Another experiment used positron-emission tomography (PET) to examine cerebral blood flow in hypnosis. The hypnotic state was related to activation of a number of mainly left-sided cortical sections and some right-sided areas.
The trend of activation shared a lot of similarities with mental imagery, from which it showed differences by the relative deactivation of the precuneus (handles visuo-spatial imagery, episodic memory retrieval and self-processing operations of the brain). This activation trend proved to be similar with mental imagery, from which it differed with the relative deactivation of the precuneus, the area of the brain in charge of episodic memory retrieval, visuo-spatial imagery and self-processing operations. Some scientists believe that under hypnosis, the subjects simply activate, to a significant extent, the brain sections used in imagination, but without actual perceptual changes.
Another functional MRI experiment shows that during hypnosis, there is controlled activity in the anterior cingulate cortex (affects learning, memory and emotions) and the visual areas of the brain. The outcome suggests that hypnosis has an influence on cognitive control by controlling activity in certain brain areas.
In many studies, hypnotizable subjects displayed considerably more brain activity in the anterior cingulate gyrus, which impacts behavior and emotions, in comparison to participants who were not hypnotized. The anterior cingulate gyrus reacts errors and assesses emotional results. Prefrontal cortex is related to with higher level cognitive processing and behavior.
Comparison of findings from several studies also puts contradictory results to fore. Several areas of the brain appear to be responsive in various experiments. This could be related to multiple experimental techniques, both in terms of equipment and hypnotic approach used in the experiments.
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