International Handbook of Clinical Hypnosis - E-Lib FK UWKS

66 INTERNATIONAL HANDBOOK OF CLINICAL HYPNOSIS
blood ¯ow rCBF), positron emission tomography PET), single photon emission
computer tomography SPECT) and functional Magnetic Resonance Imaging
fMRI).
Consistently, regional cerebral metabolism studies [unlike EEG studies reviewed
above] have reported no waking differences between low and highly hypnotizable
persons.A robust ®nding has been that highs show increases in cerebral metabolism
in certain brain regions during hypnosis for reviews, see Crawford, 1994a,b,
1996; Crawford & Gruzelier, 1992).This has been found in normally healthy
Crawford, Gur, Skolnick, Gur & Benson, 1993; De Benedittis & Longostreui,
1988; Meyer, Diehl, Ulrich & Meinig, 1989) and psychiatric Walter, 1992;
Halama, 1989, 1990) populations.Given that increased blood ¯ow and metabolism
may be associated with increased mental effort Frith, 1991), these data suggest
hypnosis may involve enhanced cognitive effort.
Among healthy individuals, De Benedittis and Longostreui 1988) found highs
but not lows showed increases in brain metabolism during hypnosis.Using the
xenon inhalation method, Crawford, Gur et al.1993) found substantial increases in
rCBF during hypnosis rest; ischemic pain with and without suggested analgesia)
in highs but not lows.During rest while reviewing past memories of a trip taken,
fCBF enhancements in the anterior, parietal, temporal and temporo-posterior
regions ranged from 13 to 28%, with the largest being in the bilateral temporal area
in highs unpublished data).Among hypnotically responsive individuals, Meyer et
al.1989) found global increases of rCBF in both hemispheres during hypnotically
suggested arm levitation.An additional activation of the temporal centers was
observed during acoustic attention.Under hypnotically narrowed consciousness
focus, there was `an unexplained deactivation of inferior temporal areas' p.48).
Discussed in greater detail below, Crawford, Gur et al.1993) found further rCBF
enhancements of orbito-frontal and somatosensory regions during hypnotic analgesia
among highs only.
Within a psychiatric population 16 neurotic, 1 epileptic) using SPECT, Halama
1989) reported a global blood ¯ow increase during hypnosis, with those more
deeply hypnotizable showing greater CBF increases than the less hypnotically
responsive.During hypnosis `a cortical ``frontalization,'' takes place particularly in
the right hemisphere and in higher areas 7 cm above the meato-orbito-level) more
than in the deeper ones 4 cm above the meato-orbital-level)' p.19).Frontal
region increases included the gyrus frontal, medial and inferior, as well as the
superior and precentral gyrus regions.These are suggestive of greater involvement
of the frontal attentional system during hypnosis.By contrast, there was a signi®cant
decrease in brain metabolism in the left hemisphere in the gyrus temporalis
and inferior region, as well as in Brodmann areas BA) 39 and 40.
Hypnotic instructions i.e., inductions and suggestions) trigger a process that
alters brain functional organization, a process that is moderated by hypnotic
susceptibility level.No longer can we hypothesize hypnosis to be a righthemisphere
task, a commonly espoused theory popular since the 1970s e.g.,