The development of brain imaging techniques has increased interest in researching phenomena such as hypnosis and placebo effects, which were previously seen as purely psychological. A literature review of the research published between 1997 and 2012, regarding the use of functional brain imaging (fMRI or PET) to study pain relief neurophysiology, indicates that hypnosis causes activity changes in specific areas of the brain. The focus of the review was on acute produced nociceptive pain.
Decreased pain ratings achieved by hypnosis are associated with activity changes in the pain network of the brain (thalamus, somatosensory cortex, insula, anterior cigulate cortex, and prefrontal cortex), the occipital areas concerned with imagery processing, and the basal ganglia which take part in voluntary movement regulation and the learning of routine behaviors (habits).
Top-down regulation can modulate pain in several ways, such as through the use of placebos or hypnosis. However, the research of these two is often done in parallel and their neurobiological relation or even similarity is yet unclear. So far the only known study conducted on both treatments has shown that highly hypnotizable individuals report feeling less pain during hypnosis than during placebo condition (McGlashan, Evans & Orne, 1969). This result implies that the effects of placebo and hypnosis are at least to some extent separate processes.
Placebo and hypnosis pain treatments differ greatly. In placebo research, a diversity of aids, such as creams and pills, are used, leading to physical sensations which are known to reduce perceived pain (Bellieni et al., 2007). In contrast, in hypnosis treatments, visualization is mainly used which results in activation of visual cortex (Faymonville et al., 2000; Rainville et al., 1999). Both treatments create brain activity in the pain network; however, parts of the brain that pertain to movement regulation (BG) and imagery processing (OC) are activated in hypnosis, but not in placebo treatments.
In the study of hypnotic analgesia, Faymonville et al. (2000) compared the ratings of pain induced on the hand by thermal stimulator, given during pleasant recollection while simply at rest or during pleasant recollection while in hypnosis. It appeared that only hypnosis affected the pain perception. PET-imaging showed that activity changes in ACC, medial prefrontal cortex, visual cortex (located in the occipital lobe) and caudate nucleus (located within the basal ganglia) during hypnosis correlated with decrease in the reported pain. Vandenhuyse et al. (2004) also found that functional connectivity between prefrontal cortex, insula and somatosensory cortex increased during hypnotic pain relief.
The changes in activity in the pain processing regions imply that the pain perception is actually diminished by hypnosis, rather than any response bias. The additional activation of prefrontal cortex means that cognitive evaluation and attention are most likely to play an important part in hypnosis induced analgesia. The correlation of prefrontal activity changes with expectations for and the magnitude of pain relief might mean that efficacy is based on changing the expectations of the participants.
Based on research results, it can be concluded that the analgesic effect which treatment with hypnosis may have on acute produced pain is probably more than just placebo effect in terms of brain functionality. This supports the previous result which indicated that placebo and hypnosis create different processes of top-down regulation in the brain (McGlashan et al., 1969).
The significance of pain is assimilated early in life. Gradually we learn the limits of our body, internalize the ways to avoid pain and the commonly accepted ways to react to it; we realize the role of pain in punishing and bringing pleasure. The pain produced in the laboratory settings is different from the pain in everyday life which usually comes unexpectedly. Still, by means of scientific study, pain alleviation can be better modeled, understood and applied. The goal of pain neurophysiology research is to utilize the obtained knowledge in the treatment of pain, to be able to use more efficiently our own abilities and resources to diminish the suffering.
Any individual with a medical or psychological problem should first consult a qualified health care provider for a diagnosis. Such a practitioner is in the best position to decide with the patient whether hypnosis is indicated and, if it is, how it might be incorporated into the individual’s treatment.
Institute of Neurosciences, Mental Health, and Addiction (INMHA) – The Brain from Top to Bottom: