Anterior commissure

Structure

It interconnects multiple cortical regions of the temporal lobes, the amygdalae, and olfactory bulbs. It is a part of the neospinothalamic tract for pain.

Function

The functionality of the anterior commissure is still not completely understood. Researchers have implicated it in functions ranging from colour perception to attention. One such study supported colour perception in callosal agenesis (those born without a corpus callosum; Barr & Corballis, 2002). Other studies have built on this to imply that the anterior commissure can be a compensatory pathway in those without a corpus callosum, presenting diffusion tensor imaging (DTI) techniques to better elucidate the anterior commissure and how it might be implicated in various functions (Winter & Franz, 2014).

Sexuality

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.

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. However, because range is defined only by the two most extreme data points in a group, the existence of a single heterosexual male with an exceptionally large anterior commissure for his group (an outlier) 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.

A later report by Byne et al. (2001) noted that We 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. Also, a study by Lasco et al. (2002) said:We examined the cross-sectional area of the AC in postmortem material from 120 individuals, and found no variation in the size of the AC with age, HIV status, sex, or sexual orientation.

Other animals

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, 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).

Gallery

File:Slide12qq.JPG|Anterior commissure

References

References

1. Patestas, Maria A.. (2016). "A Textbook of Neuroanatomy". Wiley-Blackwell.
2. (2014). "Implication of the anterior commissure in the allocation of attention to action". Front Psychol.
3. (2002). "The role of the anterior commissure in callosal agenesis". Neuropsychology.
4. Allen, LS. (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.
5. (1993). "Human sexual orientation: The biological theories reappraised". Archives of General Psychiatry.
6. "Range in Statistics - The Difference Between the Maximum and Minimum".
7. "Statistical Outliers - Extreme Datapoints".
8. (2001). "The Interstitial Nuclei of the Human Anterior Hypothalamus: An Investigation of Variation with Sex, Sexual Orientation, and HIV Status". Hormones and Behavior.
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.
10. Ashwell, Ken (2010). The Neurobiology of Australian Marsupials: Brain Evolution in the Other Mammalian Radiation, p. 50
11. Armati, Patricia J., Chris R. Dickman, and Ian D. Hume (2006). Marsupials, p. 175
12. Butler, Ann B., and William Hodos (2005). Comparative Vertebrate Neuroanatomy: Evolution and Adaptation, p. 361