Connection Controversy
"The Corpus Callosum (Fig. 733) is the great
transverse commissure which unites the
cerebral hemispheres and roofs in the lateral
ventricles."-- Gray's Anatomy Online. The debate over sexual dimorphism in the corpus callosum, the largest connection between the left and right hemispheres of the human brain, went on for years, and in fact is still debated to greater and lesser degrees.
Credit for beginning this argument seems to belong with DeLacoste-Utamsing and Holloway (1982), who reported that the splenium (or posterior part) of the corpus callosum was more bulbous in women than in men. They suggested that this difference might be related to suggested sex differences in lateralization (specialization to one side) of visuospatial function.
However, DeLacoste-Utamsing and Holloway's paper was attacked for its small sample size, and failures in appropriately age-matching subjects. Weis et al (1989) suggested that they did not accurately match for sex(!) and in their computer modeled study, did not find sex differences in the splenium. Bell and Variend (1985) did not find differences in children, and Allen et al. (1991) confirmed the lack of differentiation in children. Interestingly, Hwang et al. (2004) claimed to find differences in newborns. Richard Smith (2005) examined the types of statistical analyses used to study this debate, and concludes that a difference, while small, does exist.
Personally, I find it incredibly amusing that a debate the size and shape of an object can go on for 20 years. I could think of no better way to leave off before the holiday. Of course, if my family were debating it, by this time, the splenium of the corpus callosum would be twenty feet high, hung with twinkle-lights, and have somehow insulted my aunt. I'll be taking tomorrow and Friday off for the U.S. Thanksgiving holiday. See you on Monday.