Hypnotic hallucination alters evoked potentials

Beyond imagination: Hypnotic visual hallucination induces greater lateralised brain activity than visual mental imagery

Hypnotic suggestions can produce a broad range of perceptual experiences, including hallucinations. Visual hypnotic hallucinations differ in many ways from regular mental images. For example, they are usually experienced as automatic, vivid, and real images, typically compromising the sense of reality. While both hypnotic hallucination and mental imagery are believed to mainly rely on the activation of the visual cortex via top-down mechanisms, it is unknown how they differ in the neural processes they engage. Here we used an adaptation paradigm to test and compare top-down processing between hypnotic hallucination, mental imagery, and visual perception in very highly hypnotisable individuals whose ability to hallucinate was assessed. By measuring the N170/VPP event-related complex and using multivariate decoding analysis, we found that hypnotic hallucination of faces involves greater top-down activation of sensory processing through lateralised neural mechanisms in the right hemisphere compared to mental imagery. Our findings suggest that the neural signatures that distinguish hypnotically hallucinated faces from imagined faces lie in the right brain hemisphere.

Prolonged exposure to highly rhythmic music affects brain dynamics and perception

Rhythmic stimulation is a powerful tool to improve temporal prediction and parsing of the auditory signal. However, for long duration of stimulation, the rhythmic and repetitive aspects of music have often been associated to a trance state. In this study we conceived an auditory monitoring task that allows tracking changes of psychophysical auditory thresholds. Participants performed the task while listening to rhythmically regular and an irregular (scrambled but spectrally identical) music that were presented with an intermittent (short) and continuous (long) type of stimulation. Results show that psychophysical auditory thresholds increase following a Continuous versus Intermittent stimulation and this is accompanied by a reduction of the amplitude of two event-related potentials to target stimuli. These effects are larger with regular music, thus do not simply derive from the duration of stimulation. Interestingly, they seem to be related to a frequency selective neural coupling as well as an increase of network connectivity in the alpha band between frontal and central regions. Our study shows that the idea that rhythmic presentation of sensory stimuli facilitates perception might be limited to short streams, while long, highly regular, repetitive and strongly engaging streams may have an opposite perceptual impact.

The Power of mind: Blocking visual perception by hypnosis

The present study investigated the effects of suggestion on the processing of visual stimuli. Participants counted rare visual stimuli presented on a screen, once during a hypnosis condition where they were suggested that their vision of the screen is blocked by a virtual wooden board in front of their eyes and once during a control condition without suggestion. In the hypnosis condition, counting performance was about 20% worse than in the control condition. At the same time, the P3b amplitude of the event-related brain potential was about 37% reduced. Smaller P3b amplitudes were significantly associated with deficient counting performance, and this effect was largest in participants who reported the blockade as real. In contrast, earlier brain responses (N1, P2) that reflect basic processing of the visual stimuli were not affected by the suggested blockade. We conclude that the suggestion of the blockade affects later stages of visual perception, leaving early processes intact. This illustrates the impact of suggestions and the power of mind.

Hypnosis in Cancer Care

Cancer affects a growing proportion of the population as survival improves. The illness and its treatment brings a substantial burden of symptoms, including pain, anxiety, insomnia, and grief. Here, the uses of hypnosis in the treatment of these cancer-related problems will be reviewed. The utility of measuring hypnotizability in the clinical setting will be discussed. The current neurobiology of hypnotizability and hypnosis will be reviewed. Methods and results of using hypnosis for pain control in acute and chronic settings will be presented. Effects of hypnotic analgesia in specific brain regions associated with pain reduction, notably the dorsal anterior cingulate cortex and the somatosensory cortex, underlies its utility as a potent and side-effect free analgesic. Methods for helping those with cancer to better manage their anxiety, insomnia, and grief will be described. These involve facing disease-related stressors while dissociating the experience from somatic arousal. Given the serious complications of medications widely used to treat pain, anxiety, and insomnia, this article provides methods and an evidence base for wider use of techniques involving hypnosis in cancer care. Altering patients' perception of pain, disease-related stress, and anxiety can help change the reality of their life with cancer.

An Electrophysiological and Psychophysical Analysis of Hypnotic Visual Hallucinations

We examined the physiological and behavioral concomitants of high hypnotizable subjects reporting the capacity to hypnotically hallucinate. Subjects were required to perform a lexical decision task under baseline and four hypnotic hallucination conditions: obstructive, transparent, negative, and semantic. Analyses were conducted on various evoked potential components and psychophysical indices (RTs, sensitivity, response bias). Overall, hypnotic hallucinations did not alter VEPs over baseline; however, more liberal analyses indicated that the obstructive hallucination produced suppressions in the VEPs at P1 (left occipital), P2 (midline parietal) and P3 (midline parietal) compared to baseline. P1 latencies were also larger in the obstructive condition. Lexical decisions took longer in the hallucination conditions, and both sensitivity and response bias were reduced in these conditions. The relationship of these indices to attention are discussed.

Induction Technique: Beyond Simple Response to Suggestion

The hypnotic induction is intended to induce hypnosis. This implies that what is sought is intended to go beyond what might be wrought by mere suggestion, expectancy, and social influence. The experimentally controlled research showing that the induction makes a difference and how small changes in wording of suggestions can produce orthogonal responses is briefly reviewed. This article explains the principles of induction and three critical phases of hypnotic induction in detail. An arm levitation scripted protocol demonstrating how to respond to the patient using the three phases to maximize responses to hypnotic suggestions is presented.

Seeing Blue As Red: A Hypnotic Suggestion Can Alter Visual Awareness of Colors

Some highly hypnotizable individuals have reported changes in objects' color with suggestions given in normal waking state. However, it is not clear whether this occurs only in their imagination. The authors show that, although subjects could imagine colors, a posthypnotic suggestion was necessary for seeing altered colors, even for a hypnotic virtuoso. She reported posthypnotic color alterations also selectively in response to specific target shapes in briefly presented object arrays. Surprisingly, another highly hypnotizable person showed a very different pattern of results. The control participants could not simulate virtuosos' results by applying cognitive strategies. The results imply that hypnosis can alter the functioning of automatic visual processes but only in some of the most hypnotizable individuals.

Hypnotic Olfactory Hallucinations

Olfactory hallucinations (smelling odors that are not present) are intrusive and disruptive yet challenging to investigate because they cannot be produced on demand. In this study, the authors attempted to model olfactory hallucinations using hypnotic suggestions. We gave some subjects a suggestion to smell an odor in the absence of a real odor (positive hallucination) and gave others a suggestion to smell nothing in the presence of a real odor (negative hallucination). High hypnotizable individuals who received the positive hallucination reported intense smells whereas those who received the negative hallucination reported a reduction in intensity. These suggestions also influenced later recall about frequency of odor presentation. Findings are discussed in terms of reality monitoring and differences between positive and negative hallucinations.

Posthypnotic suggestion alters conscious color perception in an automatic manner

The authors studied whether a posthypnotic suggestion to see a brief, masked target as gray can change the color experience of a hypnotic virtuoso. The visibility of the target was manipulated by varying the delay between the target and the mask that followed it. The virtuoso's subjective reports indicated that her conscious color experience was altered already at short delays between the target and the subsequent mask. The virtuoso's objectively measured pattern of responding under posthypnotic suggestion could not be mimicked either by control participants nor the virtuoso herself. Due to posthypnotic amnesia, the virtuoso was unaware of suggestions given during hypnosis. Importantly, the virtuoso could not alter her color perception without a hypnotic suggestion. These results suggest that hypnosis can affect even a highly automatic process such as color perception.

Neuro-hypnotism: prospects for hypnosis and neuroscience

The neurophysiological substrates of hypnosis have been subject to speculation since the phenomenon got its name. Until recently, much of this research has been geared toward understanding hypnosis itself, including the biological bases of individual differences in hypnotizability, state-dependent changes in cortical activity occurring with the induction of hypnosis, and the neural correlates of response to particular hypnotic suggestions (especially the clinically useful hypnotic analgesia). More recently, hypnosis has begun to be employed as a method for manipulating subjects' mental states, both cognitive and affective, to provide information about the neural substrates of experience, thought, and action. This instrumental use of hypnosis is particularly well-suited for identifying the neural correlates of conscious and unconscious perception and memory, and of voluntary and involuntary action.

Is human information processing conscious?

Investigations of the function of consciousness in human information processing have focused mainly on two questions: (1) Where does consciousness enter into the information processing sequence, and (2) how does conscious processing differ from preconscious and unconscious processing? Input analysis is thought to be initially “preconscious” and “pre-attentive” - fast, involuntary, and automatic. This is followed by “conscious,” “focal-attentive” analysis, which is relatively slow, voluntary, and flexible. It is thought that simple, familiar stimuli can be identified preconsciously, but conscious processing is needed to identify complex, novel stimuli. Conscious processing has also been thought to be necessary for choice, learning and memory, and the organization of complex, novel responses, particularly those requiring planning, reflection, or creativity.

The present target article reviews evidence that consciousness performs none of these functions. Consciousness nearly alwaysresultsfrom focal-attentive processing (as a form of output) but does not itselfenter intothis or any other form of human information processing. This suggests that the term “conscious process” needs reexamination. Consciousnessappearsto be necessary in a variety of tasks because they require focal-attentive processing; if consciousness is absent, focal-attentive processing is absent. From afirst-person perspective, however, conscious statesarecausally effective. First-person accounts arecomplementaryto third-person accounts. Although they can be translated into third-person accounts, they cannot be reduced to them.

Hypnotic behavior: A social-psychological interpretation of amnesia, analgesia, and “trance logic”

This paper examines research on three hypnotic phenomena: suggested amnesia, suggested analgesia, and “trance logic.” For each case a social-psychological interpretation of hypnotic behavior as a voluntary response strategy is compared with the traditional special-process view that “good” hypnotic subjects have lost conscious control over suggestion-induced behavior. I conclude that it is inaccurate to describe hypnotically amnesic subjects as unable to recall the material they have been instructed to forget. Although amnesics present themselves as unable to remember, they in fact retain control over retrieval processes and accommodate their recall (or lack of it) to the social demands of the test situation. Hypnotic suggestions of analgesia do not produce a dissociation of pain from phenomenal awareness. Nonhypnotic suggestions of analgesia and distractor tasks that deflect attention from the'noxious stimuli are as effective as hypnotic suggestions in producing reductions in reported pain. Moreover, when appropriately motivated, subjects low in hypnotic suggestibility report pain reductions as large as those reported by highly suggestible hypnotically analgesic subjects. Finally, the data fail to support the view that a tolerance for logical incongruity (i.e., trance logic) uniquely characterizes hypnotic responding. So-called trance-logic-governed responding appears to reflect the attempts of “good” subjects to meet implicit demands to report accurately what they experience.