Title page for ETD etd-051399-164549

Type of Document Dissertation
Author Horton, James Edward
Author's Email Address j_horton@clinch.edu
URN etd-051399-164549
Title Hypnotizability and Corpus Callosum Morphology
Degree PhD
Department Psychology
Advisory Committee
Advisor Name Title
Crawford, Helen J. Committee Chair
Bell, Martha Ann Committee Member
Downs, J. Hunter III Committee Member
Franchina, Joseph J. Committee Member
Prestrude, Albert M. Committee Member
Stephens, Robert S. Committee Member
  • Hypnotic Analgesia
  • Hypnotizability
  • Attention
  • Morphology
  • Corpus Callosum
  • Pain
  • Magnetic Resonance Images
  • Frontal lobe
  • Anterior Cingulate
  • Psychology
  • Functional Magnetic Resonance Imaging
Date of Defense 1999-04-19
Availability unrestricted
Hypnotizability and Corpus Callosum Morphology


James E. Horton

Committee Chair: Helen J. Crawford, Ph.D.

Department of Psychology


In general, highly hypnotizable individuals ("highs") have exhibited greater abilities to focus attention and inhibit pain than low hypnotizable individuals ("lows"). Furthermore, highs appear to have faster neural processing than lows. The present study investigated differences between lows and highs in morphological volume of some brain structures associated with inhibitory and excitatory neural processing, particularly the corpus callosum (CC). Participants were 18 healthy university students, aged 18 to 29, with no history of concussion or medical disorders. They were in a functional Magnetic Resonance Image (fMRI) study examining the neurophysiology of pain and hypnotic analgesia (Crawford, Horton, Harrington, et al., 1998; Downs et al., 1998). As assessed by the group version (Crawford & Allen, 1982) of the Stanford Hypnotic Susceptibility Scale, Form C (SHSS:C; Weitzenhoffer & Hilgard, 1962), there were eight highs (four women and four men; SHSS:C M = 11.0) and 10 lows (five men and five women; SHSS:C M = 2.1). Highs were able to successfully eliminate perception of pain and distress to experimental noxious stimuli. Their anatomical MRIs were measured to assess relationships between brain structure volume (CC, medial cortex, anterior brain regions) and hypnotizability. In comparison to lows, highs had a significantly larger CC volume in the rostrum and isthmus, inferred to reflect larger transcallosal axon diameter or greater axon myelination. For highs, but not lows, there were significant relationships between forebrain volume and the total CC, rostrum, and splenium. Findings provide support for the neuropsychophysiological model of Crawford and her associates (e.g. Crawford, 1994a, 1994b; Crawford & Gruzelier, 1992) proposing a more effective attentional system of inhibitory processes in highs than lows. Furthermore, the data suggest that the more effective systems of attentional and inhibitory processes enhanced neural processing speed, and interhemispheric transfer times seen in highs than lows, may be associated with morphological differences in certain anterior and posterior CC regions. These regions are known to be involved in the allocation of inhibitory and excitatory transfer of information between hemispheres.

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