Poster
# 37
Poster |
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6th Internet World Congress for Biomedical Sciences |
Marcelle Bartolo Abela(1)
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[Neuroscience] |
[Physiology] |
So even though theories of hypnosis are numerous and quite diverse in nature, the somewhat conflicting but co-existing data presented tends to support the dissociated control theory of hypnosis, as well as supporting rather strongly the theory of hypnosis as a state in its own right, because the evidence demonstrates that hypnosis is distinctly different from either normal waking or sleep, and is not on a continuum between the latter two states: occipital increases in theta-1 amplitude (De Pascalis et al 1998), rCBF, and delta activity reflect the alteration of consciousness associated with decreased arousal and possible facilitation of visual imagery (Rainville et al 1999), increased mean theta power also suggesting the intensification of attentional processes (Crawford 1989, 1990, 1994, Crawford and Allen 1983, Crawford, Clarke, Kitner-Triolo 1996, De Pascalis 1998, Gruzelier 1998, Sabourin et al 1990) and imagery enhancement (Sabourin et al 1990), which visual processes have been shown to depend on occipital activity (D’Esposito et al 1997, Kosslyn et al 1995). The critical properties of the hypnotic image have been proposed not as stimulus components, or propositions giving rise to the experience of the image, but as response propositions associated with overt behavior, processing of the latter being conceptualized as a negative feedback system between the brain and the effector site (Heynemann 1990).
Frontal rCBF increases (Crawford et al 1993, Rainville et al 1999) are associated with suggestions for altered perception, possibly reflecting the verbal mediation of said suggestions, working memory, and top-down processes involved in the re-interpretation of the perceptual experience (Gruzelier 1998, Rainville et al 1999), and evaluation of cortical activity has shown that frontal areas of the left hemisphere control the degree of inclusion of foci of increased activity, specific and non-specific for each type of activity, and possibly even regulate the way of information transformation (Sviderskaia, Korol’kova, and Selitskii 1990). Bilateral increases in the inferior frontal gyri (Rainville et al 1999) indicate increased activity in the prefrontal association cortex and Broca’s area - i.e., the areas where the elaboration of thoughts and word formation occur respectively (Guyton 1992), while decreases in rCBF in the right inferior parietal lobule, left precuneus, and posterior cingulate gyrus (Rainville et al 1999) indicate decreased activity in areas having to do with spatial and object recognition (Romanes 1993), thus agreeing with current neuroscientific views that deeper encoding leads to greater blood flow in the left inferior prefrontal cortex (Brodmann’s areas 45, 46, 47) and the inferior and middle frontal gyri (Brodmann’s area 10) (Gazzaniga, Ivry, and Mangun 1998).
Concurrently electro-dermal responding, visual ERP’s, and the Stroop interference test involve the left hemisphere in some hypnotic phenomena such as the concentrated attentional focus, and the role of language in the establishment of hypnotic reality (Jasiukaitis et al 1997), in keeping with recent findings and theories about a left-basis for synthetic or generational capabilities (Corballis 1991), and a neuro-evolutionary model of a left-hemisphere dopaminergic activation system for the implementation of predetermined motor programs (Tucker and Williamson 1984). Such a system - i.e., the mesolimbic dopaminergic system - in fact, feeds mainly into the nucleus accumbens, amygdala, anterior caudate nucleus, and anterior cingulate gyrus (all powerful behavioral control centers) and dopamine is a neurotransmitter which, in excess, causes dissociation of an individual’s drives and thought patterns (Guyton 1992): such a pathway is seen as part of a gating mechanism governing the translation of motive states into overt motor responses (Mogenson, Jones, and Yim 1980). So this is in keeping with more recent models of hypnosis, which is considered to involve largely the left hemisphere (Rainville 1998).
Meanwhile, neurophysiological evidence also demonstrates the activation of the right hemisphere and subcortical mechanisms during hypnosis (Cikurel and Gruzelier 1989, Gruzelier and Brow 1985, McCormack and Gruzelier 1993, Torta and Zanalda 1990), which is postulated to occur during stage III of Gruzelier’s 3-stage model of hypnotic induction (De Pascalis and Penna 1990, Gruzelier 1998) and during emotional processing (Crawford, Clarke, and Kitner-Triolo 1996), with possibly direct action on the mesolimbic structures and hypothalamus, following reduced cortical activity (Torta and Zanalda 1990). This implies direct activation of the encoding and retrieval mechanisms of the brain, and the major output pathway of the limbic system respectively among others: the hippocampus, whose inhibitory action facilitates the habituation of the orienting response with stimulus repetition (Gruzelier 1998, Pribram and McGuinness 1975) and recordings of which by intracranial electrodes has been shown to be activated by hypnosis (De Benedittis and Sironi 1988), primarily encodes and consolidates knowledge in long-term memory (Gazzaniga, Ivry, and Mangun 1998). Additionally, the hippocampus seems to be involved in the explicit retrieval of significant experiences and not merely attempts to retrieve information (Schacter et al. 1996), since PET studies have shown that implicit and explicit retrieval of information is subserved by separate brain systems (Gazzaniga, Ivry, and Mangun 1998). In fact, the left hippocampus is activated for the encoding of verbal tasks, while the right is activated for the encoding of perceptual tasks, which in turn activates the left dorsolateral prefrontal cortex - i.e., part of the SAS and also the predominant site for information encoding and retrieval (ibid.), since storage occurs in a variety of cerebral cortical areas. Activation of various hippocampal parts occurs by almost any type of sensory experience, and stimulation of such parts results in hallucinations that cannot be suppressed, although the person knows such to be unreal. Meanwhile, the amygdala has been shown to be functionally inhibited by hypnosis (De Benedittis and Sironi 1988), in keeping with its mainly excitatory exertive influences on electrodermal orienting activity (Gruzelier 1998, Pribram and McGuinness 1975). Meanwhile, the hypothalamus is the major output pathway to the brain stem, diencephalon, cerebrum, and infundibulum, thus controlling most of the vegetative and endocrine body functions additionally to having control centers, the stimulation of which gives rise to profound effects on emotional behavior (Guyton 1992).
Even more specifically it is the thalamus, posterior commissure, pretectal zone, and Cajal and Darschewitsch nuclei which are neuroanatomically correlated with the upward gaze, “eye rolling”, and trance type changes of consciousness (Orengo-Garcia 1998), the thalamus acting as the main relay station via which cortical and sub-cortical structures communicate, due to its innumerable two-way connections with all cortical areas (Guyton 1992). So the neuro-anatomical and -physiological substrates of hypnosis definitely implicate the thalamus as a general relay station, for directing sensory and other signals to appropriate cortical and cerebellar regions; the hypothalamus as the controller of secondary behavior in conjunction with the entire limbic system, which regulates behavior, emotions, and motivation (ibid.); and the hippocampus for the evaluation of whether inputs should access long-term memory stores or otherwise, and whether such incoming information should consolidate events in long-term memory or otherwise. This has obvious implications for confabulation, with such being demonstrated to happen more in high hypnotizables (Laurence, Slako, and LeBeau 1998), because the Papez circuit connected to the diffuse thalamic system permits the selective inhibition of cortical areas, which inhibition prevents the checking of the accuracy of incoming information against that stored in the neocortical areas, the thalamic network in turn mediating the reduction or intensification of neural conduction to the limbic system and hippocampus, thus being instrumental in excluding sensory impressions (Kroger 1977). Moreover, results from previously mentioned intracranial electrophysiological studies also show that the content of an introspectively reportable experience of an event may be modified considerably, in relation to the actual content of the originating mental events (Libet 1993), because such content is in itself formed by neuronal activities in which there is some delay between the initial cerebral event (i.e., the neuronal priming by the gist of an occurrence), and the development and actual appearance of the conscious experience of it, during which delay the conscious function can evaluate its options (ibid.). So not only can there be (and generally is) a difference between what is actually registered unconsciously and what is reported verbally (especially initially) by the subject, but there may also be an instantaneous difference between what is actually registered unconsciously at the instance something happens and the immediate awareness of it milliseconds later, before being removed from awareness and stored unconsciously.
Also implicated during hypnosis is presumably Wernicke’s area, since it is here that the interpretation of the ultimate meanings of almost all types of sensory information occurs (Guyton 1992), and the temporal lobes for the activation of experiential and interpretive memory sequences (Kroger 1977), because electrical stimulation of certain areas of these lobes was found to result in flashbacks to seemingly random events in the subject’s past (Penfield 1959). Meanwhile, a substantial amount of evidence demonstrating distinct differences in the neurophysiological substrate of hypnosis in high versus low hypnotizables argues in favour of the adminstration of reliable hypnotizability tests such as the HIP or the TAS during clinical situations, to determine the best induction and treatment strategies. Highs show:
- Greater sustained and automatic attentional abilities (Crawford 1989, 1994, Crawford and Allen 1983, Crawford, Clarke, and Kitner-Triolo 1996, Crawford et al 1998, De Pascalis 1998, Gruzelier 1998, Laurence, Slako, and Le Beau 1998, Nadon, Laurence, and Perry 1987) as well as greater automatic information processing (Laurence, Slako, and Le Beau 1998) and faster habituation and reaction times (Crawford, Horton, and Lamas 1998, Gruzelier 1998), probably due to more frontal to posterior connections, greater coherence between anterior brain regions, shorter propagation times (Ray, Blai, Aikins, Coyle, and Bjick 1998), and anterior disconnection (Kaiser et al 1997).
- Better ignoring of irrelevant environmental stimuli than do lows, such attentional differences being reflected in underlying neurophysiological differences in the far fronto-limbic attentional system (Crawford 1994, Gruzelier 1998) implicating the anterior cingulate gyrus, limbic system, and SAS as previously discussed.
- Greater evidence of central inhibitory processes (Gruzelier 1998), particularly the left hemisphere, in response to hypnotic suggestions (Gruzelier and Warren 1993).
- Greater hemispheric asymmetries (Crawford, Clarke, and Kitner-Triolo 1996, De Pascalis and Penna 1990, De Pascalis and Perrone 1996, De Pascalis et al 1998, Gruzelier and Brow 1985, Sabourin et al 1990) with greater right hemispheric activity.
- Greater vagal efferent activity (De Benedittis et al 1994).
- Increased attenuation of evoked P1 and N1 ERP’s (De Pascalis 1994, Zachariae and Bjerring 1994).
- Greater skin conductance levels (Wickramasekera, Pope, and Kolm 1996).
- Greater rCBF and bilateral CBF increases (Crawford et al 1993).
- Greater increases in the right temporal lobe during auditory stimulation (Jutai et al 1993).
- Greater levels of emotional experiences, especially negative, and a greater ability to access affect (Crawford 1989, Crawford and Allen 1983, De Pascalis et al 1987, 1989, 1998), implying greater use of the imagination (Ray 1997, Ray, Blai, Aikins, Coyle, and Bjick 1998) as demonstrated by a consistent pattern of chaos dimensionality (Ray, Blai, Aikins, Coyle, and Bjick 1998).
- The use of both dissociation and absorption (Bartis and Zamansky 1990, Ray 1997) to achieve the hypnotic state and its phenomena.
- The ability to reduce both the sensory-discriminative - i.e., tissue (Cheek 1994)and motivational-affective components of pain (Price and Barber 1987), resulting in significantly greater pain intensity reduction (De Pascalis et al 1998).
- More effective attention-processing systems in normal everyday experiences, hypnosis often involving an amplification of such underlying abilities (Crawford et al 1998).
Therefore it is evident that highs utilize a greater amount of imagery and also employ both absorption and dissociation rather than absorption only, to enter and maintain the hypnotic state as opposed to lows, who use more cognitive activity and absorption only, to enter and maintain hypnosis. Absorption is defined by Tellegen and Atkinson as the individual’s disposition to experience episodes of total attention on a certain type of event which becomes particularly relevant (De Pascalis 1998).
Another finding is that it is hypnotizability, defined as susceptibility - accurately classifiable by neural networks in terms of EEG (Ray, Blai, Aikins, Coyle, and Bjick 1998) and which is an enduring trait (Piccione, Hilgard, and Zimbardo 1989) reflective of underlying individual differences in information processing (Crawford et al 1998) - plus motivational factors, and not suggestibility that moderates emotional processing (De Pascalis et al 1998), and opposite 40-Hz hemispheric activity is involved in patient use of imagery and dissociation: a significant relationship exists between 40-Hz EEG activity production and hypnotizability (De Pascalis and Penna 1990, De Pascalis et al 1987, 1989, 1998) with the 40-Hz EEG spectral amplitude increasing as a function of hypnotizability (De Pascalis 1998) or focused arousal (Sheer 1989), and highs display opposite 40-Hz hemispheric asymmetries during the processing of emotional material, with positive emotions such as happiness resulting in increased production of 40-Hz activity in the left frontal and central scalp regions, and negative emotions such as sadness, anger, or fear increasing activity in the right central and posterior regions and decreasing activity in the left hemisphere (De Pascalis et al 1987, 1989, 1998). This is wholly in keeping with data showing that negative suggestions stimulate greater use of the imagination than positive suggestions, consequently leaving a greater imprint on the mind than positive occurrences, negative-sentence suggestions having been shown to have affirmative affects, regardless of activity level (Miyashita and Monzen 1998). This effect of negative suggestions has also been confirmed by cortical ERP’s of hypnotic suggestions, which show that the structure of the latter is crucial (Barabasz et al 1999), since greater affect is experienced by highs rather than lows as previously indicated. Meanwhile, the more susceptible the individual to hypnosis, the greater the shift found towards the left ear (Levine, Kurtz, and Lauter 1984) or contralateral hemisphere (De Pascalis and Perrone 1996, Gruzelier and Brow 1985), in turn greater use of the imagination which seems more active in highs: such activation is also supported by EEG’s showing a switch of electrical activities from the left to the right hemisphere in right-handed persons during hypnosis (Bick 1989).
So differences in brain activity might be partially related to differences between experiencing a hypnotic suggestion or otherwise (De Pascalis and Penna 1990), again implying the dissociation and absorption versus absorption only factor, and other variables such as patient individuality. However, although hypnotizability is considered inheritable, because twin studies have shown the percent of hypnotizability of twins with common living to be higher than that of an appropriate value of twins with separate living (Bauman and Bul’ 1981), such inheritability is definitely not sex controlled by an autosomal gene with incomplete penetrance as claimed, because there is no concordance between the two groups and such also have a common environment.
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[Neuroscience] |
[Physiology] |
