What brain wave states are most correlated with deep hypnosis?
Hypnotic states are associated with increased theta wave activity. Hypnotically susceptible participants also exhibit hemispheric beta wave asymmetry, but non-susceptible participants do not (Sabourin, Cutcomb, Crawford and Pribram, 1990).
- Sabourin, M. E., Cutcomb, S. D., Crawford, H. J., & Pribram, K. (1990). EEG correlates of hypnotic susceptibility and hypnotic trance: Spectral analysis and coherence. International Journal of Psychophysiology, 10(2), 125-142.
There is a really nice and recent review about the current state of research regarding hypnosis, which also cites the resource of another answer here). I will quote here the part about EEG studies but would recommend to read the whole article (if you can't access the article, sci-hub can probably help you).
3.1. The EEG spectrum
Historically, the most popular approach to understanding the neural substrates of hypnosis has been to examine EEG correlates of hypnotizability and changes in the EEG spectrum which occur when hypnosis is induced (e.g., Lee et al., 2007; for a comprehensive listing of studies, see Hinterberger et al., 2011; Vaitl et al., 2005). Many of these studies were “fishing expeditions”, conducted in the hopes that they would yield interesting results, rather than tests of specific hypothesis about the nature or locus of electrocortical changes associated with hypnosis. Still, they were not always without some theoretical rationale, however weak. For example, in the late 1960s it was suggested that hypnotizability and hypnosis were associated with increased density of alpha activity in the EEG – a hypothesis which drew strength from early reports of increased alpha density in Zen and yoga meditation, as well as the meditation-like experiences once thought to be produced by EEG alpha biofeedback. Similar considerations, as well as speculations concerning the relevance of 40-Hz activity to focused arousal, perceptual binding, and consciousness itself, prompted investigation of the gamma band of the EEG (DePascalis, 1999, 2007). Finally, in a manner reminiscent of the 19th-century analogy between hypnosis and sleep, the association between theta activity and hypnagogic imagery led some investigators to focus on this portion of the EEG spectrum (Sabourin et al., 1990; Williams and Gruzelier, 2001).
The most thorough of these studies was reported by Ray et al., who took advantage of advanced EEG technology to examine alpha, beta, and theta activity recorded separately from frontal, temporal, parietal, and occipital sites of both left and right hemispheres in hypnotizable and insusceptible male and female college students before and after a hypnotic induction (Graffin et al., 1995; Ray, 1997). As might be imagined, given the 3 × 4 × 2 × 2 × 2 × 2 design, the results of this experiment were quite complex. Analysis of baseline differences, before hypnotic induction, revealed higher theta power in hypnotizable compared to insusceptible subjects, especially in frontal and temporal areas. Hypnotizable subjects showed greater resting alpha activity only in the temporal area. The induction of hypnosis decreased theta activity in hypnotizable subjects, while increasing it among insusceptibles, particularly in parietal and occipital areas. Alpha activity generally increased across all sites in all subjects, consistent with enhanced relaxation and reduction of visual activity. Graffin et al. interpreted the changes in theta as indicative of heightened concentration among hypnotizable subjects, but the fact that theta activity decreased in hypnotizable subjects and increased in insusceptible subjects suggests that, following the induction of hypnosis, both groups of subjects were actually in very similar cortical states.
I would say the summary is: It's complicated.
I am studying hypnotherapy at University and this is what I have learnt.
During the induction stages of hypnosis, the body becomes more and more relaxed and the brain enters changing levels of brain wave pattern. There are five brainwave frequencies, however there are four main different brainwave patterns when looking at hypnosis. These are Beta wave pattern, Alpha wave pattern, Theta wave pattern and Delta wave pattern as measured by an EEG (Electroencephalograph).
In the fully engaged and focused state, the brain will show a Beta wave pattern which is from 15 to 40 cycles per second
In a restful state, the brain will show an Alpha wave pattern which is from 9 to 14 cycles per second
In a deeper state of hypnosis, similar to dreaming and some meditative states, the brain shows a Theta wave pattern which is from 4 to 8 cycles per second
And in the deepest state of hypnosis, the brain shows a Delta wave pattern which is from 1 to 4 cycles per second and it is associated with deep dreamless sleep. The deeper the sleep, the higher the amount of delta waves.
The other brainwave frequency is Gamma (40Hz - 70Hz) associated with Processing of various attended stimuli (visual, auditory, touch) and the grouping of the various features of a given stimulus, particularly visual, into a coherent whole.
An important point is that there is no such thing as a “gamma state” of mind. Gamma waves largely play a supporting – though integral- role in the brain. From an EEG point of view, they will be present mostly while a subject is awake, but they will always be supported by other waves in the beta, alpha, theta, or delta ranges.
Brainwave patterns change in a gradual way. That is to say that it will not switch immediately from say 27Hz (27 cycles per second - Beta Waves) to 2Hz (2 cycles per second - Delta Waves). The frequency of brainwaves gradually decreases and increases as required. The speed of gradual change in brainwave frequency however can be fast or slow depending on the individual and the ability of the hypnotherapist. During reorientation, the brainwave patterns will gradually increase towards the Beta waves bringing the client back to full state of awareness.
All the above mentioned brainwave frequencies are normally present together in the brain. However, the dominant frequency in the EEG pattern determines what shall be called the current state of the brain. If the amplitude of the alpha range frequencies is highest, then the brain is said to be in the alpha stage. Note, that other frequencies still exist and it is impossible to give any "exact frequency your brain is operating on." However, for simplification purpose, it is often assumed that such a single frequency exists.
In general, we are accustomed to using the beta brain rhythm. When we diminish the brain rhythm to alpha, we put ourselves in the ideal condition to learn new information, keep facts, perform elaborate tasks, learn languages and analyse complex situations etc. Meditation, relaxation exercises, and activities that enable the sense of calm, also enable this alpha state. Considered as an integral part of the relaxation process before sleep. The alpha frequency band has been studied extensively in meditations of various kinds (like Zen, TM etc) and in almost all cases an increase in the alpha waves has been noted during meditation.
In the Theta state associated with dreams, deep meditation, sleep, and hypnosis, this is seemed to be involved with short-term memory. It is a state of somnolence with reduced consciousness. The theta-state is described by sleep researchers as stage 1 sleep or the twilight state. In this state, subjects pass out of the alert alpha-state into a theta-state in which they lose their sense of lying in bed, though still being awake.
Subjects can be easily awoken from this stage of sleep, and it has many interesting properties. For a brief time as we lie in bed at night, neither fully awake nor yet asleep, we pass through a twilight mental zone like a state of reverie. Many people associate this drowsy stage with hallucinatory images, more fleeting and disjointed than dreams, and compare it to the viewing of a speeded-up, jerky series of photographic slides. A host of artists and scientists have credited the imagery of this twilight state with creative solutions and inspiration for their work.
Meditative states associated with the increased presence of delta waves seem to occur mostly in very experienced practitioners, possibly because entering a delta state and maintaining consciousness at the same time is tremendously difficult.
Excellent observations. Read my article online The Dream as Posthypnotic Command Here is the Abstract The posthypnotic command is issued in deep hypnosis when a subject’s brainwaves are in theta mode of 4-7 cycles per second. This is the same frequency that the dream state features. It suggests that dreaming and deep hypnosis are equivalent states. The word hypnosis, meaning a condition of sleep, suggests that the ancients understood this equivalence. When a subject in deep hypnosis is commanded to execute a certain task at a given time after ‘waking up’, the subject will do so at exactly the designated time. When asked for a reason for his action, the answer will never be correct, for while under hypnosis he was asked by the hypnotist to forget the command. But the subject will certainly have a perfectly rational explanation no matter how absurd the order may have been. This is precisely the case when we are asked to give an explanation for any action we have executed. If my hypothesis is right, our answer to the same question is equally wrong, yet perfectly rational. Indeed, while we have no idea where our motivation arises and where our ideas come from, we are in the same position of darkness as the hypnotised subject. My research in dreams has convinced me that dreams are the source of our inspiration and motivation. Evidence for this comes from creative people who have received ideas from their dreams or have been presented with solutions by them to their problems. Famous scientific discoveries have been made with the help of dreams by Thomas Edison, Kekulé, Otto Loewi and Elijah Howe, for instance. Among the men of creative writing Robert Louis Stevenson stands out, for he deliberately invoked his dreams to provide him with new plots for stories. But he also suspected that the honing and reworking of his dream plots was also done for him by his “Brownies and Little People” of the night. Like the posthypnotic suggestion, the dream has a timing device determining when a dream or part of it should manifest in waking time. Perhaps the most convincing evidence for this is Michael Barnsley’s twenty-year nightmare that taunted him to put the wires of a matrix in order. Since he had no idea of what the matrix was supposed to do, he was naturally unable to solve the problem posed to him. The nightmare only ceased after he met Benoit Mandelbrot who had by then invented a computer program for fractal math, a program that provided all the necessary information for Barnsley to understand the dream that ended the nightmares by providing him with the solution of the confused wires of the dream matrix. This dream gave him the circuitry that led to the invention of image compression software. The wet dream, which occurs at the end of the night of dreams and is a heightened sexual state, indicated by morning erections, shows that the sexual content of the dream forces the dreamer, who by then is free of the nightly muscle inhibitors, to act it out. This leads us to surmise that the sexual aspect of the dream tends to manifest on the dream day. A thorough investigation of this circumstance proved the inference right. This led me to devise a test of the dream’s power to compel us to execute its content. It entails the interpretation of the sexual meaning of the dream and making a prediction on account of it. The corresponding manifestations verify my theory. I found support in my view that dreams were posthypnotic commands in the experimentations of Professor Libet, who found that our decisions were made unconsciously up to half a second before we became conscious of them. They demonstrate that our decisions are made unconsciously. There is no better explanation of this process than the dream. In short, the subjects tested by Libet would have dreamt the experiments ahead of time, thus providing them with the appropriate dream memory. It was this that determined the unconscious choices of the experimentees, registering half a second before becoming conscious fact. The somnambulist provides another factor that supports the hypothesis that dreams are posthypnotic commands. He, like the wet dreamer, is in a state of reduced muscle inhibition and is consequently free to act out his dreams. I realise that there is considerable controversy with regard to the causes of sleepwalking. But the difference between the wet dreamer and the somnambulist is minimal. Indeed, why would the dream state be constrained by muscle inhibition if it were not for the prevention of acting out what the dreamer experiences? Clearly somnambulism is a most illustrative case of dreams being posthypnotic commands. There can be little doubt that the dream is very much a posthypnotic command, signalling that our life is in the hands of a Master Hypnotist of infinite capacity.
There does seem to be changed activity in the brain, however. The most notable data comes from electroencephalographs (EEGs), measurements of the electrical activity of the brain. Extensive EEG research has demonstrated that brains produce different brain waves, rhythms of electrical voltage, depending on their mental state. Deep sleep has a different rhythm than dreaming, for example, and full alertness has a different rhythm than relaxation.
In some studies, EEGs from subjects under hypnosis showed a boost in the lower frequency waves associated with dreaming and sleep, and a drop in the higher frequency waves associated with full wakefulness. Brain-wave information is not a definitive indicator of how the mind is operating, but this pattern does fit the hypothesis that the conscious mind backs off during hypnosis and the subconscious mind takes a more active role.
Researchers have also studied patterns in the brain's cerebral cortex that occur during hypnosis. In these studies, hypnotic subjects showed reduced activity in the left hemisphere of the cerebral cortex, while activity in the right hemisphere often increased. Neurologists believe that the left hemisphere of the cortex is the logical control center of the brain; it operates on deduction, reasoning and convention. The right hemisphere, in contrast, controls imagination and creativity. A decrease in left-hemisphere activity fits with the hypothesis that hypnosis subdues the conscious mind's inhibitory influence. Conversely, an increase in right-brain activity supports the idea that the creative, impulsive subconscious mind takes the reigns. This is by no means conclusive evidence, but it does lend credence to the idea that hypnotism opens up the subconscious mind.
Whether or not hypnosis is actually a physiological phenomenon, millions of people do practice hypnotism regularly, and millions of subjects report that it has worked on them. In the next section, we'll look at the most common methods of inducing a hypnotic trance.