The neuroscience of hypnosis: What we know and what we don't

The topic of hypnosis has long been shrouded in mystery and intrigue. From stage performers to therapeutic applications, it seems everyone has an opinion on what hypnosis is and how it works. However, the neuroscience of hypnosis is still a relatively new area of research that has begun to shed light on the mechanisms behind this fascinating phenomenon.

While much is still unknown, recent studies have revealed intriguing insights into how the brain responds to hypnosis, including changes in neural activity and connectivity. By exploring what we know about the neuroscience of hypnosis, we can increase our understanding of this enigmatic process and its potential application as a therapeutic tool in hypnotherapy.

Here are some definitions of what hypnosis is from some of the most well-known hypnotists:

"A state of consciousness involving focused attention and reduced peripheral awareness characterized by an enhanced capacity for response to suggestion." (Elkins et al., 2015).

"It is characterised by four main components: absorption (in an imaginative experience), dissociation (from the environment), suggestibility (to the suggestions made by the therapist; Spiegel, 1991), and automaticity (non-voluntary response relevant to the content of a communication intended to be a suggestion; Weitzenhoffer, 2002)."

"Hypnosis modulates self-awareness and decreases environmental awareness." (Demertzi et al., 2011, 2015).

The three definitions, despite very different wording, all define a similar experience, one in which the user is in a heightened state of internal focus with less attention on the external. Very different to sleep or relinquished control, often the characteristics synonymous with hypnosis. 

Brain activity and functional connectivity associated with hypnosis

As technology improves, researchers have more ability to investigate mind states like hypnosis. In 2017, Cerebral Cortex Journal published a study with the title Brain Activity and Functional Connectivity Associated with Hypnosis. The researchers used fMRI (functional magnetic resonance imaging) to understand the brain in hypnosis. 

The investigations focused on three parts of the brain - the default mode network, the executive control network, and the salience network. 

The Default Mode Network 

The Default Mode Network (DMN) is a network of brain regions active when an individual is not actively engaged in a task or focused on the outside world. Often referred to as the "resting state" network, it is most active when the mind is at rest, and not actively processing sensory information from the external environment.

The DMN has a range of cognitive processes, such as self-reflection, social cognition, and mentalising (the ability to understand the mental states of others). It also plays a part in the formation and retrieval of autobiographical memories, and the integration of past experiences with current sensory information.

The DMN has also been associated with maladaptive patterns of thought, such as rumination, self-referential thinking, and mind-wandering. 

The Executive Control Network

The Executive Control Network (ECN) is a network of brain regions involved in higher-order cognitive functions, such as working memory, attentional control, cognitive flexibility, and decision-making. Often referred to as a "task-positive" network, as it is most active when an individual is engaged in a goal-directed task or actively processing information from the external environment.

The ECN is thought to help regulate cognitive processes, allowing individuals to adapt their behaviour in response to a change in environmental demands. It is also involved in the suppression of unwanted or irrelevant information, allowing individuals to focus their attention on the most relevant aspects of a task. The ECN and DMN appear to have opposing patterns of activity. While the DMN is most active during periods of rest and self-reflection, the ECN is most active during periods of cognitive engagement and goal-directed behaviour. 

Salience Network

The Salience Network (SN) is a network of brain regions involved in the detection and integration of salient (noticeable and important) stimuli, such as emotional or sensory information, that is particularly relevant to an individual's current goals or interests.

The SN is thought to play a critical role in detecting and responding to stimuli that are most relevant to an individual's needs, goals, or motivations, and redirecting attention and resources accordingly. It is also involved in the regulation of emotional and physiological responses to these stimuli, helping individuals adapt to changing environmental demands.

The SN has been implicated in some neuropsychiatric disorders, including depression, anxiety, and post-traumatic stress disorder (PTSD). Dysregulation of the SN has been associated with difficulty processing and regulating emotional responses, and may contribute to the development of these disorders.

The research results

The researchers split the group into non-hypnotisable, highly hypnotisable, and low-hypnotisable. In the highly hypnotisable research participants, they found: 

Reduced activity in the dorsal anterior cingulate cortex, part of the salience network dealing with cognition and motion control. This part of the brain is a critical region of the brain for the regulation of cognitive, emotional, and behavioural processes.

Significantly enhanced connectivity between the left dorsolateral prefrontal cortex (LDLPFC), the left insular cortex (LIC) and the right supramarginal gyrus (RSMG). These three distinct regions of the brain are involved in various cognitive and emotional processes. 

The LDLPFC helps regulate cognitive and emotional processes, such as working memory, attentional control, and decision-making. Dysfunction in the LDLPFC has been associated with difficulty in regulating emotional responses and maintaining attention. 

The LIC has a range of cognitive and emotional processes, including interoception, emotion processing, empathy, and social cognition. Dysfunction in the LIC has been associated with difficulty in regulating emotional responses and interoceptive awareness, and may contribute to the development of neuropsychiatric disorders like depression, anxiety, and addiction. 

The RSMG, located in the posterior portion of the parietal cortex, stands out for its role in the perception and processing of touch and proprioception, as well as in the integration of sensory and motor information during action planning and execution. Dysfunction in the RSMG has been associated with difficulty in processing and integrating sensory information, as well as in the coordination of motor responses.

Overall, the LDLPFC, LIC, and RSMG are critical regions of the brain for the regulation of cognitive and emotional processes, and dysfunction in these regions has been implicated in some neuropsychiatric disorders. Having the ability to significantly enhance the connectivity between these areas of the brain could help reduce the risk of some neuropsychiatric disorders.

Decreased low-frequency amplitude in the dorsal anterior cingulate cortex (dACC). This is a region of the brain involved in some cognitive and emotional processes, including attentional control, decision-making, error detection, conflict monitoring, and pain perception.

One of the primary functions of the dACC is to monitor and detect conflicts in cognitive processing, such as when two or more pieces of information or actions conflict. The dACC detects errors and adjusts behaviour to prevent future errors. In addition to its role in cognitive processing, the dACC is also involved in the emotional processing of pain and other aversive stimuli.

Studies have shown that the dACC activates during the experience of physical pain, as well as during the anticipation of pain. Therefore, as hypnosis reduces the activity of this part of the brain, it could help the user manage pain. The dACC has been implicated in some neuropsychiatric disorders, including depression, anxiety, obsessive-compulsive disorder (OCD), and addiction.

Dysfunction in the dACC has been associated with difficulty in regulating emotional responses, attentional control, and decision-making, and may contribute to the development of these disorders.

Increased connectivity between the bilateral dorsal lateral prefrontal cortex (DLPFC) and the ipsilateral insula. The DLPFC and the ipsilateral insula are two distinct brain regions, functionally connected in the brain through the fronto-insular pathway. The insula has functions, including emotional processing, interoception (the perception of internal bodily sensations), and social cognition. The fronto-insular pathway is thought to play a critical role in the regulation of emotional and cognitive processes, including attention, working memory, decision-making, and the experience of pain.

Specifically, studies have shown that the DLPFC is active in the top-down regulation of emotional responses, such as the suppression of negative emotions, and the connections with the insula mediate this regulation.

Additionally, the insula has been shown to play a role in the detection of salient events in the environment, which is thought to be important for attention and decision-making. The DLPFC is also involved in these processes and may modulate insular activity to facilitate these functions.

The researchers suggest this increased connectivity may reflect the increased ability to engage in tasks with reduced anxiety using hypnosis. 

The final finding for the highly hypnotisable group was a decoupling of the default mode network and the executive control network during hypnosis. This was unexpected. The researchers believe this dissociation between the ECN and the DMN in response to hypnotic induction likely reflects engagement in the hypnotic state and detachment from internal mental processes, such as mind wandering and self-reflection. They say it is a positive sign, as it reinforces the idea of hypnosis as a different state of consciousness, rather than a reduced level of arousal - i.e. relaxation. The fMRI also showed this change in the low hypnotisable people. 

In conclusion

From this research, it is clear that hypnosis causes a change in brain state for some people. This change makes hypnosis a useful tool to use in hypnotherapy. However, this change only happens for some people.

For other people, hypnosis, in combination with tools such as breathing techniques or mindfulness exercises, is still beneficial for calming the body, introspection, and taking control of your own thoughts and reactions.