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Non-state theorists contend that there is no need to infer the existence of a special hyp-notic state or trance to account for responsiveness to suggestions. However, non-state theorists do not deny that hypnosis reflects genuine alterations in consciousness. Based on findings that changes in brain activation in a number of regions can be observed during hypnosis (Faymonville et al. 2000; Rainville et al. 2000), Peter Bloom (2004) declared ‘We now have the proof: Words change physiology!’ We agree with this assess-ment (e.g. see also Kirsch and Lynn 1995). However, the power of words, much less the power of imagination, is not under dispute. Finding physiological concomitants of a hypnotic induction and suggestions would be consistent with all theories, including non-state theories. All subjective experiences are assumed to have physiological sub-strates or correlates that are potentially localizable or detectable (Hyland 1985;

Wagstaff 2000; Willlingham and Dunn 2003). According to non-state theorists, psy-chophysiological correlates of hypnosis are inevitable and expected by-products of ‘the various activities engaged in by the subject as he or she responds to the demands of hypnotic suggestions by variously relaxing, sifting attention, concentrating, “drifting”, imagining, “letting go”, thinking, complying and so on, depending on the suggestion’

(Wagstaff 2000, p. 156).

There is a surprising degree of consensus, among researchers identified with both a non-state and weak interpretation of the altered state position, that hypnosis is not a uni-form state, but rather reflects what participants ‘do’ during hypnosis (see Kihlstrom 2003), which varies as a function of the suggestions they receive. As Kihlstrom (2003) observed, ‘At one moment, the hypnotic subject is experiencing a direct motor sugges-tion; at another, a challenge suggessugges-tion; at another, suggestion for a positive or negative hallucination; at yet another, a suggestion for amnesia or posthypnotic response. Each of these hypnotic activities and experiences is likely to be mediated by a different brain module or system, and it is not clear that they will have anything in common’ (p. 181).

Kihlstrom (2003) further noted that Crawford and Gruzelier’s proposal ‘that hypnosis selectively activates a variety of cortical and subcortical structures and systems, depend-ing on the task required of the subject (Crawford 2001; Gruzelier 1998) … marks the abandonment of the search for unique correlates of hypnosis or hypnotizability, because it predicts quantitative, but not qualitative differences between hypnosis and control conditions’ (p. 181).

In a similar vein, Horton and Crawford (2004) recently concluded that different pat-terns of electroencephalographic (EEG) activity depend upon the task being experienced because hypnosis is not a unitary state. They point to hypnosis studies showing that enhanced theta is observed ‘when there is task performance or concentrative hypnosis (e.g. Crawford 1990; Sabourin et al. 1990; Graffin et al. 1995), but not when the highly hypnotizable individuals are passively relaxed, somewhat sleepy and/or more diffuse in their attention (Graffin et al. 1995; Williams and Gruzelier 2001)’ (p. 140). Jasiukaitis et al.

(1997) also underlined the importance of the task in determining hemispheric activation during hypnosis. Woody and McConkey (2003) imply that different patterns of brain activation will correspond to different suggestions insofar as disparate abilities, presum-ably related to different cortical activation patterns, may be required to respond to sugges-tions, say for hand levitation versus hypnotic analgesia. They also proposed that people with different abilities may produce the same response in different ways, presumably via different cortical structures or mechanisms.

Research from a variety of quarters supports the suggestion-bound nature of psy-chophysiological activity. Barabasz et al. (1999) found that participants responded very differently depending on the suggestion they received for hypnotic blindness. In all cases, subjects reported that they could not perceive the target stimulus. When subjects received suggestions to produce blindness by creating a hypnotically obstructed halluci-nation, their P300 component of the event-related potential (ERP) in response to the visual stimulus was reduced, as expected. The authors suggested that this occurred because the suggestion conveyed the demand that perception of the stimulus would diminish. However, when subjects received suggestions that they would not see or hear anything at all, the amplitude of the P300 component increased, contrary to expecta-tions. The authors attributed the unexpected finding as due to participants’ surprise that they could still perceive the stimulus to some extent, despite suggestions to mask perception of the stimulus.

Wagstaff (1998) proffered a non-state, strategy-based account of the findings. More specifically, he contended that the results make sense if subjects strategically concentrate on the stimulus to ‘obliterate it’, but are unsuccessful in doing so. The fact that cognitive strategies did come into play is suggested by the following example cited by Barabasz et al. (1999): ‘One [participant], showing only a moderate ERP amplitude attenuation in the obstructive condition, noted she pictured a cardboard box in front of the computer monitor, but “I pictured a rather small box that didn’t block the entire screen!”’

De Pascalis and Carboni (1997) asked subjects to imagine a glove that covered a wrist that was exposed to electric stimuli of mild intensity. The authors interpreted a reduction of P300 peak in the posterior region of the left hemisphere as ‘the product of a compet-ing effect between the hallucinated obstructive mental image and the processcompet-ing of somatosensory stimulation’ (Ray and De Pascalis 2003, pp. 151–152). These results are consistent with strategic attempts to reconcile suggestion and reality rather than an unvarying altered state that is produced by hypnosis across subjects.

The modulating effects of suggestions are likewise evident in other studies of hypnotic analgesia. DePascalis et al. (1999) determined that a focused analgesia suggestion (focus

on hand and produce an obstructive hallucination of a glove covering it) produced more pronounced task-related changes in evoked potential responses (P300 and N2) than both suggestions for dissociated imagery (i.e. imagine oneself floating out of the body and ‘up in the air’) and deep relaxation. The study showed that the nature of the suggestion does affect brain activity; however, it is difficult to conclude much beyond this, insofar as the nature of the suggestion is conflated with task difficulty. That is, the dissociative imagery may have been more difficult to produce than the obstructive imagery, as implied by the authors, who argued that the latter condition might have required more processing capacity. Moreover, relaxation-based strategies may not promote distraction and may therefore be less effective in diminishing pain in general. However, what is clear is that if hypnosis produces an altered state that yields a consistent biological marker of trance, then this marker should be apparent regardless of how suggestions are worded or what strategies are used.

Two studies conducted by Rainville and his associates’ underline this conclusion. In their first study (Rainville et al. 1997) using positron emission tomography (PET), they used hypnotic suggestions to alter the affective dimension of pain sensation. This resulted in changes in ratings of the unpleasantness of painful heat stimuli, and modula-tion in activity in the anterior cingulate cortex (ACC). However, the suggesmodula-tions did not alter ratings of stimulus intensity, and did not affect somatosensory brain structures (S1 or S2). In their second study (Hofbauer et al. 2001), when participants received sug-gestions that modulated pain sensation (see also Rainville et al. 1999a), one of the somatosensory structures (S1) was activated, but no changes were observed in the ACC. In summary, consistent with a non-state view (and therefore also with a ‘weak’ state view), the physiological correlates of hypnotic responses depend heavily on the task, the partic-ipants’ cognitive activities and the specific suggestions presented, rather than the produc-tion of a singular, fixed, or unique altered state following an inducproduc-tion (Wagstaff 1998;

Ray and DePascalis 2003).

Participants’ responses to suggestions for altered perceptions are correlated with physi-ological responses. For example, Spiegel’s (2003) review indicates that hypnotic sugges-tions can modulate ERP amplitude changes in the sensory association cortex with respect to: (1) visual stimuli (Spiegel 1985; Spiegel and Barabasz 1988; Jasiukaitis et al.

1996; DePascalis and Carboni 1997); (2) olfactory stimuli (Barabasz and Lonsdale 1983);

(3) somatosensory perceptual stimuli (Spiegel et al. 1989; De Pascalis et al. 1999, 2001);

and (iv) suggestions for hypnotic numbness (Spiegel et al. 1989). Changes in the somatosensory cortex have also been observed, as a function of hypnotic analgesia suggestions for ischaemic pain (Crawford et al. 1993).

Hypnotic suggestions can produce impressive changes in brain activation that closely resemble those produced by actual perceptual experiences. Szechtman et al. (1998) demonstrated that highly suggestible subjects exhibited increased regional blood flow in the right ACC, as assessed by PET, in response to suggestions to hallucinate a person’s voice during hypnosis (Szechtman et al. 1998; Woody and Szechtman 2000), in contrast to imagining and baseline. In the hallucinating group, a strong positive correlation was found between activation (as measured by regional blood flow by PET) in this region and

the participants’ ratings of their experience (match with external reality r= 0.95; clarity r= 0.85). Woody and Szechtman (2000) are clear that the intent of their study was to use hypnosis to study the nature of hallucinations, rather than to study the nature of hypno-sis itself. Indeed, their study did not evaluate subjects who were not hypnotized but received the identical suggestion to hallucinate a person’s voice.

Kosslyn et al. (2000) found that hypnotic suggestions produce changes in blood flow in the brain similar to those that occur in the actual perception of colour. During PET scan-ning, highly suggestible subjects who received suggestions to see a grey scale pattern in colour showed activation in their left and right hemispheres, regardless of whether they were shown the stimuli in colour or grey scale. In contrast, when the subjects received a suggestion to see the colour pattern as grey scale, the same brain regions exhibited decreased activation, regardless of whether the stimuli were in colour or grey scale. The authors reported that the results were obtained only during hypnosis in the left hemi-sphere. In contrast, in the right hemisphere, blood flow changes reflected instructions to perceive colour versus grey scale, regardless of whether subjects had been hypnotized.

Kosslyn et al. (2000) concluded that their findings ‘support the claim that hypnosis is a psychological state with distinct neural correlates and is not just the result of adopting a role’ (p. 1297). This conclusion is problematic. First, it betrays the common misconcep-tion that non-state theories reduce hypnotic response to conscious role-playing (or sim-ulation) and are not genuinely experienced. Secondly, definitive conclusions regarding hypnosis are not warranted in that subjects in the hypnosis and mental imagery control received very different instructions with different task demands. Subjects in the hypnosis group were asked to alter their perception of the stimuli as much as possible and to let the investigators know when they had successfully added or drained the colour. However, in the no-hypnosis condition, when subjects were asked to perceive the grey scale stimu-lus in colour or vice versa, they were asked to try to ‘remember and visualize’ the stimustimu-lus in its other form. By telling hypnotized subjects that they will see something, and telling visualizing subjects to remember something, suggestion is confounded with induction.

This precludes any conclusions about the altered state hypothesis. As Kosslyn (1999; see also Kosslyn 1994) aptly noted, ‘it has long been known that changing one aspect of a task can lead subjects to adopt qualitatively different strategies’ (p. 1286), in which case different structures and processes might be used, and hence different areas activated.

Lacking appropriate controls, it is tempting to interpret a hypnotically suggested effect as an indicator of a trance. Raz et al. (2002) reported that a hypnotic suggestion to see words as if they were in a foreign language reduced Stroop interference in highly sug-gestible subjects. Because Stroop inhibition is widely regarded as automatic, some readers might interpret this as a major shift in information processing and hence as an altered state (although Raz et al., to their credit, did not make this claim). Raz et al. (2006) have since replicated these results with unhypnotized as well as hypnotized subjects, although they used a post-hypnotic suggestion in their initial study. Their data confirm that sug-gestion can modulate the Stroop effect, but they also indicate that this does not require the induction of hypnosis. Altered Stroop inhibition may be an altered state, but it is not necessarily a hypnotic state and does not reveal the presence of a trance.