A new and innovative neuroimaging study published in NeuroImage has helped foster a deeper understanding of what makes some of us ready-made putty in a hypnotist’s hands, and others, a stubborn thorn in their sides that may require a different approach.

Hypnosis is a poorly understood and often controversial technique that induces a special state of receptive concentration, allowing the filtering of sensations or thoughts, so as to modify the content of conscious awareness in favour of hypnotic suggestion.

The astounding results of hypnotic phenomena undoubtedly have impressive clinical applications. Take the novel hypnotic sedation technique for fully awake brain tumor removal surgery just published in the journal Neurosurgery in the video below (WARNING: graphic footage):

The success of these surgical techniques is based heavily on the assumption that patients in such extreme medical situations naturally enter a trance-like state making them highly receptive to hypnotic induction and suggestion. In extreme settings like this, most of us are assumed to be highly hypnotizable.

Yet outside of the operating theatre in our day-to-day lives, some of us will far more readily fall into trance than others.

This is perhaps why the infamous hypnotist Derren Brown takes the time to carefully select which person in the crowd will be ideal for a challenging trick; he selects a highly hypnotizable and suggestible member of the audience to more readily ensure amazement, wonder and awe. A learned master of profiling people for hypnosis, he needs no neuroimaging device to look inside his audience members’ brains.

Hypnotic susceptibility in the brain

Behavioural studies on hypnotic susceptibility thus far have produced conflicting results. This has lead to two opposing hypothesis regarding how attentional processes account for differences in hypnotizability:

“One view proposes that individuals who are highly susceptible to hypnosis are better able to focus attention, allowing more efficient concentration and filtering. Another view argues that highs may indeed be particularly adept at controlling attention but through the decoupling of executive control from sensorimotor processing, such that selective attention is actually reduced and behavior more easily driven by automatic processes.”

In other words, the first theory posits that those that are more easily hypnotised have more focused attention, allowing for effective concentration on and response to the hypnotic suggestion.

For the second theory on the other hand, individuals that are more easily hypnotized would have less selective attention control and instead have a more automatic response that allows for more flexible attention in responding to the distracting hypnotic suggestion, known as dissociated control of attention.

The neuroimaging study in question attempted to address this conflict by using a uniquely modified Flanker task and compared the scans of individuals less or more readily hypnotised while performing the task outside of hypnotic trance.

The Eriksen Flanker Task involves the participant detecting whether a central stimulus is in a certain mode (e.g. facing left or right in the example below), while attempting to ignore other distracting stimuli surrounding it. The distracters surrounding the key stimulus are either congruent (e.g. facing the same direction) or incongruent (e.g. facing the opposite direction), where incongruent distracters are more distracting, resulting in a longer response time.

They found that both those with high and low hypnotic susceptibility took longer to respond to incongruent distracters, as expected. However, those with high hypnotic susceptibility appeared less efficient as they generally took longer to respond in the presence of both congruent and incongruent distracters, for similar accuracy.

Moving from comparing those with high and low susceptibility to hypnosis in the behavioural dimension to the brain dimension was very revealing:

“…components of the fronto-parietal executive network implicated in monitoring (anterior cingulate cortex; ACC), adjustment (lateral prefrontal cortex; lPFC), and implementation of attentional control (intraparietal sulcus; IPS) were differently activated depending on the hypnotizability of the subjects…”

Specifically, highly suggestible people had less efficient detection of conflict and implementation of attentional control than those less suggestible, in line with their slower response times in the Flanker task. This was represented by having less activity in the ACC (responsible for response conflict detection) and IPS (responsible for implementation of control).

Additionally, when directing attention in the flanker task, highly suggestible people had more recruitment of the right inferior frontal gyrus (rIFG) in the prefrontal cortex. Importantly, the rIFG had greater connectivity with the default mode network (DMN) than those with less hypnotic susceptibility.

The DMN is most activated at rest, during more internal and non-task orientated activities, with network activity negatively correlating with activity in regions involved in willful direction of attention and executive functions. The researchers interpreted this as the rIFG being involved in the detection of salient or task relevant cues while being in tight dialogue with internally and externally driven processes, which may permit higher flexibility in attention and underlie a greater ability to dissociate attention and attend to hypnotic induction ques. Thus, the new and improved Flanker task supports the dissociated control of attention hypothesis of hypnotic susceptibility.

Considering the DMN is differentially activated in response to stressful situations, it is reasonable to assume that the relatively high hypnotic induction rate found with hypnosurgery may also be linked with stress response-related DMN activity, irrespective of one’s general suggestibility outside of such situations. This may also be why instant hypnotic induction is the technique of choice for less suggestible people, where the hypnotists makes use of DMN-heavy automatic responses like handshakes, to direct the individuals attention towards hypnotic induction in a less conscious manner.

These advances in understanding the fundamental principles of hypnotic susceptibility in the brain may eventually lead to tailoring the increasingly popular and diverse clinical applications of hypnosis for greater effectiveness, depending on one’s level of susceptibility and suggestibility of course.

References

Cojan, Y., Piguet, C., & Vuilleumier, P. (2015). What makes your brain suggestible? Hypnotizability is associated with differential brain activity during attention outside hypnosis NeuroImage, 117, 367-374 DOI: 10.1016/j.neuroimage.2015.05.076

Doenitz, C., Brawanski, A., & Hansen, E. (2014). The usefulness of the awake-awake-awake technique Acta Neurochirurgica, 156 (8), 1491-1492 DOI: 10.1007/s00701-014-2112-y

Soares JM, Sampaio A, Ferreira LM, Santos NC, Marques P, Marques F, Palha JA, Cerqueira JJ, & Sousa N (2013). Stress Impact on Resting State Brain Networks. PloS one, 8 (6) PMID: 23840493

Zemmoura I, Fournier E, El-Hage W, Jolly V, Destrieux C, & Velut S (2015). Hypnosis for Awake Surgery of Low-grade Gliomas: Description of the Method and Psychological Assessment. Neurosurgery PMID: 26313220

Image via Monika Wisniewska / Shutterstock.