Brain Regions Involved in Hypnosis: Clinical Implications Sarah Hale, Gary R. Elkins, Ph.D

Sarah Hale, Gary R. Elkins, Ph.D.

Hypnosis is described as a “state of consciousness involving focused attention and reduced peripheral awareness characterized by an enhanced capacity for response to suggestion” (Elkins, Barabasz, Council, & Spiegel, 2015). The clinical uses of hypnosis include medical and psychological applications. However, it is not yet known whether the “state of consciousness” is an alteration of waking consciousness, similar to other states (i.e. meditation, mindfulness, yoga), or unique to hypnosis. This paper reviews the relevant literature on hypnosis to identify the brain regions that research has suggested may be most likely associated with hypnosis. Studies utilizing electroencephalogram (EEG), magnetic resonance imaging (MRI), functional magnetic resonance imaging (fMRI), and positron emission tomography (PET) scanning were reviewed. Because of the results presented in the studies examined in this paper, I hypothesize that hypnosis can affect certain regions of the brain. Furthermore, targeting and altering activity in those brain regions could enable benefits to be achieved more quickly through hypnotherapy and similar mind-body practices.

Hypnosis and hypnotherapy have a history predating modern psychology and psychotherapy. Due to many efforts of researchers and practitioners “during the latter half of the 20th century and leading up to the present time, there has been an increasing amount of empirical testing the effectiveness of hypnotic interventions” (Elkins, 2014). Because of this, hypnosis has been shown to have applications in both the medical and psychotherapy fields. In the medical field, hypnosis has been used to treat various physical conditions, including chronic pain (Artimon, 2015; Mazzola et al., 2017), irritable bowel syndrome (Palsson, 2015), and management of hot flashes (Elkins, Fisher, Johnson, Carpenter, & Keith, 2013; Sliwinski & Elkins, 2017). Hypnosis has also been used to improve palliative care for chronic illness (Brugnoli et al., 2018). In conjunction with psychotherapy, hypnosis has been used to treat psychological disorders, such as Post-Traumatic Stress Disorder (PTSD) (Lynn, Malakataris, Condon, Maxwell, & Cleere, 2012), depression (Alladin & Alibhai, 2007; Kirsch & Low, 2013), and nicotine addictions (Green & Lynn, 2017; Pekala, 2017).

According to Landry & Raz (2017), “the hypnotic response is located at the confluence of three central factors: interindividual variability in hypnotizability, the induction procedure, and the content of hypnotic suggestions” (See Figure 1). This paper discusses the brain regions involved in each of the three central factors during hypnotic response. In most of the reviewed articles addressing hypnotizability and/or induction, induction and hypnotizability were primarily studied together and their contributions to the hypnotic response were found to be correlated (Cardeña, Jönsson, Terhune, & MarcussonClavertz, 2013; Deeley et al., 2012; Hoeft et al., 2012; Jiang, White, Greicius, Waelde, & Spiegel, 2017; Lipari et al., 2012; William J. McGeown, Mazzoni, Venneri, & Kirsch, 2009; Picerni et al., 2019). This observation illustrates that the more hypnotizable someone is, it is probable that they would have a higher response to induction.

Multiple sources found patterns of modulation in three principle neural networks when investigating hypnotizability and induction. These attentional neural networks include the Executive Control Network (ECN), the Salience Network (SN), and the Default Mode Network (DMN). The ECN is a neural network in the brain that is associated with the control of intentionality. This system is also referred to as the Central

Induction

Hypnotic Responses

Suggestion

Hypnotizability

Figure 1.Note. Adapted from “Neurophysiology of Hypnosis”, by Landry, M., & Raz, A., 2017, In G. R. Elkins (Ed.), Handbook of medical and psychological hypnosis: Foundations, applications, and professional issues, p.20

Executive Network in some sources. The main brain region associated with the ECN is the dorsolateral prefrontal cortex (DLPFC) (Deeley et al., 2012; Hoeft et al., 2012; Jiang et al., 2017; Lipari et al., 2012; William Jonathan McGeown, Mazzoni, Vannucci, & Venneri, 2015; Terhune, Cardeña, & Lindgren, 2011). The SN, composed of the dorsal anterior cingulate cortex (dACC), anterior insula, amygdala, and ventral striatum, is “involved in detecting, integrating, and filtering relevant somatic, autonomic, and emotional information using independent component analysis” (Hoeft et al., 2012). The DMN, the most recently discovered of the three networks, is described as a “network of brain regions more active during low-demand compared to high-demand task conditions and has been linked to processes such as task-independent thinking, episodic memory, semantic processing, and selfawareness” (Deeley et al., 2012). Brain regions associated with the DMN include the “posterior cingulate cortex (PCC) and other midline brain structures including the medial prefrontal cortex (mPFC)” (Jiang et al., 2017). While these networks do work independently, the SN and DMN also are connected to the ECN and have been shown to work with the ECN under some circumstances.

The third factor contributing to the hypnotic response is suggestion, which can produce one of three categories of effects: perceptive, cognitive, or motor (Halligan & Oakley, 2014). Perceptive suggestions are intended to alter visual or sensory experiences. Cognitive suggestions are intended to alter performance of relevant tasks. Motor suggestions are intended to “alter preparation, execution, and monitoring of actions” (Cojan et al., 2009; Landry & Raz, 2017). In this paper, I review relevant literature on these three types of suggestions.

By investigating the brain regions or networks implicated in each of the individual factors contributing to the hypnotic response, one can achieve a more thorough understanding of the neural processes occurring during hypnosis. Considering the various psychological and physical applications of hypnosis that have been identified, a more thorough understanding of the neural underpinnings behind the response could lead to a refinement of the approach to inducing a hypnotic response as well as an expansion of potential ameliorating applications of hypnosis as a clinical tool.

In order to find relevant sources for this review, I used the following search engines: PsychINFO, Pubmed, and Google Scholar. Keywords for searches included “hypnosis”, “brain imaging”, “neuroimaging”, and “brain correlates”. Studies that utilized different brain imaging techniques, such as EEG, MRI, fMRI, and PET were included. Since a variety of imaging techniques allows for many possible types of visualizations of the nervous system, this renders more information. Most studies analyzed healthy subjects and level of hypnotizability was reported to be low hypnotizability, medium hypnotizability, or high hypnotizability. Some studies included subjects from only one hypnotizability level, while others include subjects from all levels. Studies with subjects that had any history of psychological disorders were excluded. Seventeen studies will

Three neural networks, the ECN, SN, and DMN, commonly showed increased activity in research involving the neural correlates associated with hypnotizability and induction. The most common finding among studies discussing induction was a reduction in DMN activity, especially in individuals who are of high hypnotic ability (Deeley et al., 2012; Lipari et al., 2012; William J. McGeown et al., 2009). To explore modulation of the DMN during induction, Deeley et al. (2012) used fMRI to observe medium hypnotizable individuals (MHIs) and highly hypnotizable individuals (HHIs). They found that there was a negative correlation between self-reported hypnotic depth, and therefore absorption, and activity within the DMN. They also found increased activity in other prefrontal regions of the brain involved in attention. Lipari, et al. (2012) found similar results when investigating “pure hypnosis” (a state in hypnosis in which there are no further suggestions after induction) with a “hypnotic virtuoso”. This subject scored the highest possible score (12) on the Stanford Hypnotic Susceptibility Scale (Weitzenhoffer, Hilgard, & Kihlstrom, 1962). Using fMRI and EEG, this study found a significant decrease in activity within the DMN, as well as “peculiar activations of non-DMN areas and hemispheric Kihlstrom, 1962). Using fMRI and EEG, this study found a significant decrease in activity within the DMN, as well as “peculiar activations of non-DMN areas and hemispheric asymmetries of frontal lobe connectivity” (Lipari et al., 2012). Another study by McGeown et al. (2009) utilized fMRI to analyze differences in neural correlates among LHIs and HHIs during visual tasks both in and out of hypnosis with the goal of understanding induction. While McGeown et al. (2009) also found that there was a significant decrease in anterior DMN activity among HHIs, their study suggests that there was no other increase in any other cortical regions, which was not observed in the two previously mentioned studies. The decrease in DMN activity in HHIs suggests that HHIs are experiencing a higher degree of attention to the administered suggestions. HHIs are likely integrating the suggestions, resulting in an increased behavioral response behaviorally to the suggestions. Although various findings showed different brains regions also involved in hypnotizability, it appears that that reduced activity in DMN are common across all studies.

Another interesting finding involving the attentional neural networks is a modulation of connectivity between the ECN, SN and DMN (Jiang et al., 2017). In this study, the left and right dorsolateral prefrontal cortex (ECN), dorsal anterior cingulate cortex (dACC; SN), and posterior cingulate cortex (PCC; DMN), were observed using fMRI in order to study connectivity between the three networks during hypnosis. Among HHIs, there was a “decoupling” or decreased level of connectivity between the DLPFC and posterior cingulate cortex (PCC), a region of the DMN, explaining a deeper level of absorption and possibility of “hypnotic loss of self-consciousness and amnesia”. During induction, there was not only decreased activity in the dorso-anterior cingulate cortex (dACC), a region of the SN, but

also a higher level of connectivity between (the insula—another region of the SN) and the DLPFC (ECN). The authors suggest these actions correlate with “reduced context comparison” and “decreased attention to external environment”. Considering that the dACC has been implicated in playing a role in finding solutions to detected conflicts, it is particularly interesting that the DLPFC, the central executive area responsible for allocating attentional resources, exhibits higher levels of connectivity with this region in HHIs. This suggests that HHIs more readily detect suggestions as a conflict of interest, leading to increased allocation of attentional resources to the verbal suggestion. This, thereby, could result in an increased susceptibility to the suggestion (Jiang et al., 2017).

When comparing HHIs and LHIs, Jiang et al. (2017) found that HHIs had increased connectivity between the DLPFC and insula. The insula plays a role in self-awareness (being aware of oneself) and perception of the self (how one sees oneself). Considering that the insula is additionally implicated in the salient network which has connections to the default mode network, the insula may be involved in the allocation of attentional resources that are relevant to self-perception. It is noted that HHIs showed increased connectivity between the DLPFC and the insula. This is consistent with the function of the insula and the potential role of functional connections between the SN and the DMN. In regard to induction, the insula appears to be involved in the isolation of the self from the external environment, resulting in possibly increased attention allocated to the verbal suggestions being administered. Another study (Hoeft et al., 2012) comparing neural correlates of hypnotizability found similar results, showing HHIs having greater connectivity between the left DLPFC and SN. Subjects including twelve LHIs and HHIs were observed under fMRI and T1 MRI scans in order to compare the neural phenomena under hypnosis between the two groups. The study also found that HHIs have a greater connectivity between the dACC and DLPFC. Considering that the dACC is involved in conflict detection, it is interesting that HHIs exhibit increased levels of connectivity to the DLPFC, the executive attentional center of the prefrontal cortex responsible for the allocation of attentional resources. With higher connections between these two regions, HHIs more readily identify suggestions as relevant and important stimuli to attend to, leading to an increased focus and attention to the suggestion. This ultimately leads to an increase in individuals’ susceptibility to hypnotic suggestions.

Terhune, Cardeña, & Lindgren (2011) did not look for any of the aforementioned networks; instead they used EEG and self-reports to compare frontal-parietal phase synchrony in LHIs and HHIs. They found that HHIs showed “lower frontalparietal alpha 2 synchronization during hypnosis” than LHIs (Terhune et al., 2011). Therefore, they concluded that HHIs have a frontal-parietal network that is more easily modulated, hence allowing them to be more hypnotizable. The researchers also acknowledge, however, that an “alternative interpretation” of the results is a reflection of “group differences in the DMN”, including the medial prefrontal and lateral parietal cortices (Terhune et al., 2011).

In addition to the attentional neural networks, other studies have found additional brain regions to be involved in the hypnotic response. Cardeña, Jönsson, Terhune, & MarcussonClavertz (2013) utilized EEG in order to observe neutral hypnosis among 37 individuals with varied hypnotizability. They found that global functional connectivity was decreased following hypnotic induction. Subjective reported hypnotic depth was related to global connectivity, suggesting that reduced functional connectivity could be associated with higher degrees of hypnotizability. (Cardeña et al., 2013) Another study by Picerni et al. (2019) investigated “the association between cerebellar macro- or micro-structural variations…and hypnotic susceptibility”. They found that HHIs exhibited lower levels of gray matter volumes in various brain regions such as the right inferior temporal gyrus, insula, superior orbitofrontal cortex, etc. This suggests that increased hypnotizability is associated with lower levels of cell body presence (Picerni et al., 2019). Contrary to the association between higher levels of

hypnotizability and lower levels of gray matter volume, white matter volume appears to be increased in HHIs. This is consistent with previous research that suggests that there are increased functional connections between neural networks during the hypnotic response.

Suggestions may be considered powerful tools for modulating perceptual experiences. Among the various perceptual experiences that can be induced or modulated through suggestion, the most common throughout the literature include visual and nociceptive experiences (Aleksandrowicz, Binder, & Urbanik, 2007; Koivisto, Kirjanen, Revonsuo, & Kallio, 2013; William J. McGeown et al., 2012; Valentini, Betti, Hu, & Aglioti, 2013). In regard to potential modulations of the experience of pain through suggestion, there are various applications that have been explored in previous studies. In a study by Aleksandrowicz, Binder, & Urbanik (2007), the researchers utilized fMRI to observe neural activity relative to a control as well as a hypnotic condition receiving a pain stimulus. Each subject underwent every condition: pain stimulus, pain stimulus following an analgesic suggestion, pain stimulus under neutral hypnosis (a state in which hypnosis is induced, but no suggestion is given), pain stimulus under hypnosis following analgesic suggestion, then finally “focusing and de-focusing of attention, in an alternate fashion”. Overall, the study found decreased thalamic activity, suggesting that sensory pathways, prior to reaching areas of higher-order processing, may become modulated as a result of hypnotic suggestions. Furthermore, nociceptive processing centers exhibit attenuated levels of activity, suggesting that suggestion can modify the experience of pain at the neurophysiological level. Although reduced levels of activity are observed in some nociceptive neural processing areas as a result of suggestion, some areas have been found to exhibit increased activity. The right anterior cingulate cortex (R-ACG), for instance, exhibits increased activity as a result of analgesic suggestions, suggesting that the reception of verbal suggestions, including those relating to nociceptive experiences, are actively and not passively integrated by the subject. Further research is necessary to expand these findings in analgesic suggestions to other categories of hypnotic suggestion (Aleksandrowicz et al., 2007).

Furthemore, hypnotic suggestions related to experiences of analgesia affect specific aspects of the nociceptive experience. In a study by Valentini et al. (2013), through the use of a noxious laser pain stimulus, HHIs and LHIs were tested to observe “whether hypnotic suggestions of sensory and affective hypoalgesia or hyperalgesia differentially affected subjective ratings of laser-induced pain and nociceptive-related brain activity”. Subjects experienced an alteration of the affective domain of pain. Therefore, the pain experience was enhanced through the activation of neuroaffective processing centers. In particular, this study found modulated activity in the cingulate cortex as well as the somatosensory cortex. This phenomena indicates that conflict identification along with allocation of attentional resources results in modulation of somatosensory cortices, including those related to that of the experience of nociceptive stimuli (Valentini et al., 2013).

In addition to modulating the subjective experience of pain or nociceptive stimuli, hypnotic suggestions are capable of modulating visual perception. In a study conducted by McGeown et al. (2012), the effects of hypnosis on color perception were explored in individuals of varying degrees of hypnotizability. In order to do this, researchers utilized fMRI in order to observe responses to two visual hallucinations (i.e., seeing color when looking at a grey-scale image and seeing greyscale when looking at a color image). These hallucinations were induced via suggestions with and without a hypnotic induction. The results of this study were consistent with other studies regarding nociceptive perception. HHIs experienced altered color perception under the experience of hypnotic suggestion. Strikingly, however, this study also found that HHIs are able to experience an altered color perception regardless of whether they are being administered a hypnotic suggestion or not. Furthermore, this study found evidence of default mode network alterations in activity during hypnotic responses, indicating that attentional networks are involved in attending to suggestions whether the subject is being exposed to a hypnotic stimulus or not (William J. McGeown et al., 2012).

Visual perception can be modulated in considerably specific ways. In a study conducted by Koivisto et al. (2013), HHIs were tested in how much suggestions could alter the perceived color that they observed in briefly presented shapes. In order to investigate this, the researchers utilized EEG, then observed their two subjects’ responses as they were “briefly presented visual shapes under posthypnotic color alternation suggestions such as ‘all the squares are blue’”. Overall, there was a significant difference found in beta activity over the posterior cortex when presenting hypnotic suggestions and when not presenting suggestions. Beta-band oscillation was not observed during hypnotic suggestion, suggesting that activity levels in certain brain regions are modulated in the same way that color perception appears to be modulated in response to hypnotic suggestions (Koivisto et al., 2013).

In addition to having the capacity to modulate perceptual experiences, hypnotic suggestion has been found to be able to induce altered motor activity states, particularly in HHIs. In a study conducted by Cojan et al. (2009), the effects of hypnotic suggestion on inducing motor paralysis were explored. Subjects underwent fMRI in three conditions: “normal state, hypnotic left-hand paralysis, and feigned paralysis”. Although increased activity in areas relevant to the intention of movement were observed, such as in the right motor cortex, precuneus activity additionally increased. This increase indicates that mental imagery, a largely implicated component of the hypnotic response, began to increase self-monitoring in movement. Overall, this study found that hypnotic suggestions act through internal representations and not directly through motor inhibition. This is consistent with the previous study that found that hypnotic suggestions act through top-down influences and not necessarily through bottom-up influences (Cojan et al., 2009).

Extending the findings that hypnotic suggestion has been implicated in the alteration of motor capacities during the hypnotic response, a study by Pyka, et al (2011) aimed to investigate hypnotic paralysis by means of two sessions of fMRI. Subjects performed two sessions of fMRI, one session consisting of hypnotic suggestion of a left-arm paralysis and the other

Table 2. Summary of the Studies Focusing on Suggestion

session consisting of normal-state observations. The researchers found that specific neural networks are involved in the alteration of motor behavior through top-down influences. In particular, attentional neural networks such as the default mode network were found to have direct connections with areas such as the primary motor cortex in the frontal lobe. Furthermore, the precuneus is, again, implicated to have a significant role in mediating the role of self-referential mental imagery in maintaining the hypnotic state of heightened suggestibility. According to this study, not only does this extend to visual perception, but furthermore to the induction of altered motor behavior through hypnotic suggestion (Pyka et al., 2011).

In order to observe whether or not bottom-up influences affect the hypnotic response in relation to elicited movement, Burgmer, et al. (2013) investigated the influence of hypnotically induced paralysis of the left arm on subjects during an imitation or mimicking task. Researchers utilized fMRI in order to assess movement imitation and observation while subjects were under two conditions: hypnotic suggestion of left-hand paralysis and without. The study found heightened activity levels in higherorder areas related to conflict detection (anterior cingulate cortex), and self-representation (insula), among other cortical regions. Consistent with previous studies that found that the effect of hypnotic suggestion seems to be restricted to areas starting from the thalamus and beyond, this paper further implicates that hypnotic suggestions appear to act through topdown influences and not through direct alteration of peripheral motor regions (Burgmer et al., 2013).

In addition to being able to alter perception as well as being able to elicit movement, hypnotic suggestion has been found to be able to alter other cognitive processes. For instance, Ulrich, et al. (2015) investigated the effects of hypnotic suggestion on semantic processing. This study was centered on the effects of suggestion on how individuals extract information from verbal language. In order to observe this, subjects “performed the task once at normal wakefulness and once after the administration of hypnotic suggestions to perceive” an actual word “as a meaningless symbol of a foreign language.” Through the use of primes as forms of suggestions, in order to influence subjects during a discrimination task between pseudowords and target words, the study found that prime words had reduced effects when coupled with a hypnotic suggestion. Overall, this study suggests that semantic priming can be reduced as a result of a reduction of activity in automatic and attentive semantic processing centers, as induced by hypnotic suggestions (Ulrich, Kiefer, Bongartz, Grön, & Hoenig, 2015).

As the previously discussed study suggests, there are various other cognitive abilities, aside from perception, that can be modulated through hypnotic suggestion. Another study conducted by Facco, et al. (2014) observed nonmusician subjects who “underwent MMN recording before and during a hypnotic suggestion for amusia. MMN amplitude was recorded using a 19-channel montage and then processed using the lowresolution electromagnetic tomography (LORETA) to localize its sources”. The researchers found that the recognition of music stimuli can be altered through hypnotic suggestion. More specifically, the study found that decreased amplitudes of activity were detected in the left temporal lobe. Overall, these findings suggest that, in addition to preceptual experiences and the elicitation of movements, cognitive experiences such as language processing and aesthetic experiences such as those of music perception can be altered through hypnotic suggestion (Facco et al., 2014).

In summary, the central finding of this literature review is that there are specific neural networks that are implicated in the hypnotic response. Among these neural networks, the three, principle attentional neural networks—the salience network, the default mode network, and the executive control network— appear to be especially important in mediating the attentional component of hypnotizability, in which subjects pay increased attention to suggestions and, as a result are more susceptible to the given message. Through the interactions between these three neural networks as well as brain regions associated with selfconcept, self-movement, and perception, hypnotic suggestions can elicit altered perceptual, motor, and cognitive experiences.

Considering these extensive capabilities of hypnotic suggestions in eliciting altered perceptual, motor, and cognitive activity, the potential applications of hypnosis to ameliorate different conditions are profound. For instance, psychological conditions associated with impaired thoughts or behaviors can be ameliorated through hypnotic suggestion. Similarly, conditions involving impaired cognitive abilities can be improved through hypnotic suggestion. Overall, the potential applications of hypnotic suggestion to clinical settings are considerable. Further research is critical in continuing to expand our knowledge on the nuanced components of hypnotic responses in order better comprehend and thereby apply the technique to relevant circumstances.

I would like to thank Dr. Gary Elkins, my mentor, and Whitney Williams for guiding and supporting me in my research. Finally, I would like to thank the Baylor McNair Scholars Program for expanding opportunities for me, both in research and in life.

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