Anterior commissure

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Brain: Anterior commissure
Coronal section of brain through anterior commissure. (Label for "anterior commissure" is on left, third from bottom.)
The hypophysis cerebri in position. Shown in sagittal section. (Caption for anterior commissure is at center top.)
Latin commissura anterior
Gray's p.840
NeuroNames hier-187
NeuroLex ID birnlex_1557




The fibers of the anterior commissure can be traced laterally and posteriorly on either side beneath the corpus striatum into the substance of the temporal lobe.


The corpus callosum allows for communication between the two hemispheres and is found only in placental mammals (the eutherians), while it is absent in monotremes and marsupials, as well as other vertebrates such as birds, reptiles, amphibians and fish. The anterior commissure serves as the primary mode of interhemispheric communication in marsupials,[1][2] and which carries all the commissural fibers arising from the neocortex (also known as the neopallium), whereas in placental mammals the anterior commissure carries only some of these fibers).[3]


In 1992 Laura Allen and Roger Gorski of UCLA measured the anterior commissures of 30 homosexual men, 30 heterosexual men, and 30 heterosexual women. They found that all three groups' commissures were significantly different from one another, with homosexual males having the largest anterior commissure, followed by heterosexual women, and then heterosexual men, who had the smallest anterior commissures.[4]

In 1993, a review by Byne and Parsons criticized this research, noting that 27 of the 33 homosexual males fell within the range of heterosexual males in the study.[5] However, because range is defined only by the two most extreme data points in a group,[6] the existence of a single heterosexual male with an exceptionally large anterior commisure for his group (an outlier [7]) would cause this large range irrespective of the data from the rest of the individuals in the group. This individual's existence would not change the fact that the groups on average were quite different from one another, and that these differences were statistically significant.[4]

A later report by Byne et al. (2001) noted that


also measured the anterior commissure in the same blocks of tissue used for the present hypothalamic study (data not shown) and were unable to replicate a report [by Allen and Gorski] that its cross-sectional area is larger in women

than in men.[8]

Also, a study by Lasco et al. (2002) said:


See also[edit]


  4. ^ a b Allen, LS; Gorski, RA (Aug 1, 1992). "Sexual orientation and the size of the anterior commissure in the human brain.". Proceedings of the National Academy of Sciences of the United States of America 89 (15): 7199–202. doi:10.1073/pnas.89.15.7199. PMC 49673. PMID 1496013. 
  5. ^ Byne W., Parsons B. (1993). "Human sexual orientation: The biological theories reappraised". Archives of General Psychiatry 50: 228–239. 
  6. ^
  7. ^
  8. ^ William Byne, Stuart Tobet, Linda A. Mattiace, Mitchell S. Lasco, Eileen Kemether, Mark A. Edgar, Susan Morgello, Monte S. Buchsbaum, and Liesl B. Jones, The Interstitial Nuclei of the Human Anterior Hypothalamus: An Investigation of Variation with Sex, Sexual Orientation, and HIV Status. Hormones and Behavior 40, 86–92 (2001)
  9. ^ Lasco MS, Jordan TJ, Edgar MA, Petito CK, Byne W., A lack of dimorphism of sex or sexual orientation in the human anterior commissure. Brain Res. 2002 May 17;936(1-2):95-8.

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