Recent neuroscientific research has significantly advanced our understanding of how hypnosis alters brain activity compared to normal waking consciousness. Through sophisticated neuroimaging techniques including functional magnetic resonance imaging (fMRI), electroencephalography (EEG), and transcranial magnetic stimulation (TMS), researchers have identified distinct patterns of neural activity that differentiate the hypnotic state from normal wakefulness. These differences extend beyond simple changes in relaxation levels, revealing fundamental shifts in how the brain processes information, integrates neural networks, and maintains awareness during hypnosis.
Altered Network Connectivity and Integration
One of the most consistent findings across multiple studies is that hypnosis fundamentally alters the connectivity patterns between different brain regions. During normal wakefulness, brain regions maintain a metastable state characterized by synchronized neural activity that can flexibly reconfigure based on internal and external demands. However, this pattern changes dramatically during hypnosis.
Research from the University of Turku demonstrated that during hypnosis, the brain shifts to a state where individual brain regions act more independently of each other compared to normal wakefulness. As described by researcher Henry Railo, “In a normal waking state, different brain regions share information with each other, but during hypnosis this process is kind of fractured and the various brain regions are no longer similarly synchronized”5. This finding suggests that information processing during hypnosis occurs in a more segregated manner, with reduced integration across the whole brain8.
A study using transcranial magnetic stimulation (TMS) and EEG found that hypnosis is associated with a shift from the metastable state of normal wakeful consciousness toward more segregated connectivity. During normal consciousness, neural activity in cortical regions transiently locks into synchronized configurations that then flexibly reconfigure based on various factors. This pattern of transient locking was observed as strong, widespread activation in frontoparietal areas 150–200 milliseconds after TMS pulse. In contrast, during hypnosis, this synchronized activity failed to initiate; processing in different cortical areas remained segregated1.
Recent studies using graph theory analyses have further refined our understanding of these connectivity changes. During hypnosis, researchers observed increased network segregation (short-range connections) in delta and alpha frequency bands, alongside increased integration (long-range connections) in the beta-2 band. This higher network integration and segregation was measured particularly in bilateral frontal and right parietal electrodes, which were identified as central hub regions during hypnosis9.
Changes in Default Mode and Extrinsic Networks
Hypnosis appears to specifically modulate two important neural networks—the default mode network (DMN), associated with self-referential processing, and the “extrinsic” network, involved in processing external sensory information. Resting-state fMRI studies have revealed consistent changes in these networks during hypnosis.
Compared to control conditions like autobiographical mental imagery, hypnosis results in reduced “extrinsic” lateral frontoparietal cortical connectivity, possibly reflecting decreased sensory awareness of the external environment. Simultaneously, the default mode network shows a more complex pattern of connectivity changes: increased connectivity in bilateral angular and middle frontal gyri, with decreased connectivity in posterior midline and parahippocampal structures. These alterations are thought to relate to altered “self” awareness and posthypnotic amnesia27.
The reduced connectivity in the external awareness network appears particularly pronounced in the right supramarginal and left superior temporal areas. This decreased connection between networks involved in external awareness and those involved in self-awareness may contribute to the altered state of consciousness experienced during hypnosis, including increased absorption and reduced critical analysis of external stimuli2.
Modified Brainwave Patterns and Spectral Changes
EEG studies reveal distinct spectral power differences between hypnosis and normal wakefulness. These differences are present most notably at frequencies above 24 Hz, with higher frequencies being more pronounced during hypnosis, especially in the occipital region. Conversely, in the frontal area, hypnosis is characterized by a decrease in lower frequency ranges1.
Multiple studies have reported increased theta power (4-8 Hz) during hypnosis compared to normal wakefulness. Both subjects with high and low hypnotizability showed increased mean theta power during hypnosis, suggesting an intensification of attentional processes and imagery enhancement13. This finding has been consistent across multiple studies, though the magnitude of change varies.
More recent research using high-density EEG found specific connectivity changes across frequency bands during hypnosis: increased delta connectivity between left and right frontal regions, as well as between right frontal and parietal regions; decreased connectivity for alpha between right frontal and parietal and between upper and lower midline regions; and decreased beta-2 band connectivity between several regions including upper midline and right frontal, frontal and parietal, and between upper and lower midline regions49.
Interestingly, the relationship between hypnotic depth and brainwave activity appears consistent across studies, with theta activity showing a positive association with responsiveness to hypnosis. Some research has found greater theta amplitudes particularly in highly hypnotizable subjects, especially over the left hemisphere of the brain, suggesting that individual differences in hypnotic susceptibility may have neurophysiological markers13.
Information Processing and Neural Dynamics
During normal wakefulness, the brain processes and shares information across various regions to enable flexible responses to external stimuli. During hypnosis, however, this information sharing becomes altered in a fundamental way. Researchers have described this change as a “fractured” neural processing state where the synchronization typically seen between brain regions becomes disrupted5.
This alteration in information processing is reflected in studies measuring the Perturbational Complexity Index (PCI), which quantifies the complexity of neural responses to transcranial magnetic stimulation. Research has found that hypnosis is associated with more complex (more highly differentiated) activation patterns compared to baseline wakefulness, with significantly increased PCI throughout the TMS-evoked activation period1. This represents the first demonstration of increased PCI under a non-pathological conscious condition.
The altered complexity in brain responses during hypnosis is also evident in phase-locking measurements. During normal wakefulness, baseline phase-locking is most prominent in the 100–200 millisecond timeframe following stimulation. During hypnosis, however, decreased phase-locking is observed in this same timeframe, consistent with decreased inter-area communication in the functional network1. This reduced phase-locking suggests altered metastable dynamics during hypnosis.
Top-Down Cognitive Regulation
Hypnosis appears to achieve its effects through modulation of top-down regulatory processes in the brain. Research indicates that hypnotic responses recruit frontal networks involved in attentional regulation, control, and monitoring processes. These top-down modifications allow hypnotic suggestions to dramatically change how cognitive strategies are implemented6.
Stanford University researchers conducted groundbreaking work examining the brain activity of subjects during hypnosis sessions, identifying “three hallmarks” of brain activity during hypnotic states. One notable finding was decreased activity in the dorsal anterior cingulate, a region involved in impulse control and decision-making. This suggests that during hypnosis, the brain achieves a highly focused state with reduced distraction from competing stimuli12.
A particularly interesting finding involves a functional disconnection between the lateral prefrontal cortex (associated with cognitive control processes) and the anterior cingulate cortex (linked to cognitive monitoring) during hypnosis. This neurological decoupling may explain the dissociative experience often reported during hypnosis, where hypnotized individuals describe their responses as feeling involuntary and effortless6.
Brain Regions Specifically Altered During Hypnosis
Neuroimaging studies have identified specific brain regions that show altered activity during hypnosis. The anterior cingulate cortex (ACC) plays a particularly crucial role, with studies documenting significant activity changes during hypnotic states. This region is especially responsive to suggestions related to pain perception and emotional regulation112.
Research using positron emission tomography (PET) has examined the role of cortical regions involved in hypnosis and their response to suggestions. While hypnotic induction itself may have minimal effect on pain-related activation in areas such as the primary somatosensory cortex, secondary somatosensory cortex, insular cortex, and anterior cingulate cortex, hypnotic suggestions for increased or decreased unpleasantness significantly affect pain perception and modulate activity in these specific pain-related cortical areas1.
Studies focusing on emotional regulation have demonstrated that hypnotic suggestions can suppress unwanted thoughts and numb the conscious perception of unpleasant emotions. Experimental results show that hypnotically induced emotional numbing significantly reduces emotional and somatic responses to aversive stimuli, with corresponding changes in brain regions involved in emotion processing6.
Conclusion
The neuroscientific evidence clearly demonstrates that hypnosis represents a distinct brain state that differs markedly from normal wakefulness across multiple dimensions of neural function. The hypnotic state is characterized by altered connectivity between brain networks, changes in spectral power across frequency bands, modified information processing, and specific alterations in key brain regions involved in attention, control, and self-awareness.
These findings challenge earlier skepticism about whether hypnosis genuinely modifies neural processing and provide concrete evidence that the hypnotic state represents a fundamentally different mode of brain function rather than merely a placebo effect or role-playing behavior. As neuroimaging and electrophysiological techniques continue to advance, our understanding of the neural correlates of hypnosis will likely become increasingly refined, potentially leading to enhanced clinical applications of hypnotic techniques for conditions ranging from pain management to emotional regulation and behavioral modification.