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Archives of Sexual Behavior

, Volume 37, Issue 6, pp 857–863 | Cite as

Corpus Callosum Anatomy in Right-Handed Homosexual and Heterosexual Men

  • Sandra F. Witelson
  • Debra L. Kigar
  • Anton Scamvougeras
  • David M. Kideckel
  • Brian Buck
  • Peter L. Stanchev
  • Michael Bronskill
  • Sandra Black
Original Paper

Abstract

The results of several studies have shown that homosexual men have an increased prevalence of non-right-handedness and atypical patterns of hemispheric functional asymmetry. Non-right-handedness in men has been associated with increased size of the corpus callosum (CC), particularly of the isthmus, which is the posterior region of the callosal body connecting parietotemporal cortical regions. We hypothesized that isthmal area would be greater in homosexual men, even among right handers. Twelve homosexual and ten heterosexual healthy young men, all consistently right-handed, underwent a research-designed magnetic resonance imaging scan. We found that the isthmal area was larger in the homosexual group, adding to the body of findings of structural brain differences between homosexual and heterosexual men. This result suggests that right-handed homosexual men have less marked functional asymmetry compared to right-handed heterosexual men. The results also indicate that callosal anatomy and laterality for motoric functions are dissociated in homosexual men. A logistic regression analysis to predict sexual orientation category correctly classified 21 of the 22 men (96% correct classification) based on area of the callosal isthmus, a left-hand performance measure, water level test score, and a measure of abstraction ability. Our findings indicate that neuroanatomical structure and cognition are associated with sexual orientation in men and support the hypothesis of a neurobiological basis in the origin of sexual orientation.

Keywords

Corpus callosum Magnetic resonance imaging Sexual orientation Homosexuality Functional asymmetry Hand preference Cognition 

Notes

Acknowledgments

This work was supported by research grants NIH NS18954 and MRC 10610 to S.F.W. A.S. held an Ontario Mental Health Foundation fellowship and D.M.K. held an Ontario Graduate Scholarship, while at McMaster University. We thank Dr. Charles Goldsmith, Department of Epidemiology and Biostatistics, McMaster University, for statistical advice.

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Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  • Sandra F. Witelson
    • 1
  • Debra L. Kigar
    • 1
  • Anton Scamvougeras
    • 2
  • David M. Kideckel
    • 3
  • Brian Buck
    • 4
  • Peter L. Stanchev
    • 5
  • Michael Bronskill
    • 6
  • Sandra Black
    • 4
  1. 1.Department of Psychiatry and Behavioural NeurosciencesMcMaster UniversityHamiltonCanada
  2. 2.Department of PsychiatryUniversity of British ColumbiaVancouverCanada
  3. 3.Institute of Medical ScienceUniversity of TorontoTorontoCanada
  4. 4.Division of Neurology, Department of MedicineSunnybrook Health Sciences CentreTorontoCanada
  5. 5.Department of Science and MathematicsKettering UniversityFlintUSA
  6. 6.Imaging ResearchSunnybrook Health Sciences CentreTorontoCanada

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