Time and time again, we hear the question, what exactly is hypnosis and is there science behind 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 realms in both left and right hemispheres were excited when the subjects were instructed to perceive colors. The researchers agreed that hypnosis is indeed a one-of-a-kind psychological state and definitely doesn’t come from adopting a role.
Another fascinating observation from these studies were the hemispheric changes between non-hypnotized and hypnotized brain. When non-hypnotized subjects were instructed to perceive colors on a greyscale photograph, only right hemisphere was triggered. The left hemisphere, where reason and logic is processed, responded only during hypnosis.
Another research used positron-emission tomography (PET) to look into cerebral blood flow in hypnotized subjects. The hypnotic state was connected with activation of a lot of mostly left-sided cortical areas and some right-sided regions.
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 findings hints that hypnosis impacts cognitive control by regulating activity in particular brain areas, including early visual modules.
In multiple studies, hypnotizable subjects exhibited substantially more brain activity in the emotion and behavior-affecting anterior cingulate gyrus, as compared to participants who are non-hypnotized. The anterior cingulate gyrus reacts errors and assesses emotional results. Prefrontal cortex is linked to higher level cognitive processing and behavior.
Comparison of findings from several studies also puts contradictory results to fore. Many sections of the brain seem to be activated in different studies. This may be connected to various experimental techniques, both when it comes to equipment and hypnotic approach used by experimenters.
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