Posted by SLS on February 22, 2001, at 0:03:33
In reply to Scoooooootttttt » mars, posted by mars on February 21, 2001, at 17:59:17
> You never answer my followup questions, Scott. (I can document this.) When you have a moment, dear Scott, would you post a bit of info about what you were reading about corpus collosi (?)?
>
> yrs very truly,
>
> a very sick mars
Dear Mars,I am dismayed to here that you are suffering so. No matter how many times I read of people here who are hurting and agonizing, it never becomes any less difficult to see.
I apologize for not following-up on your post. Please don't take it personally. I have a limited amount of mental energy, and I can't always follow the continuation of a thread. Actually, I am becoming more reluctant to post things because I would then have the responsibility to follow up and answer people's questions.
There still seems to be a preponderance of evidence that indicates a true gender difference in the size and orientation of the corpus callosum along with many other structures and pathways. I thought it a good idea to include at the end of this post an abstract that is a rather lengthy, but broad treatment of gender differences in both brain morphology and psychometrics.
I could not find one abstract that I alluded to in my prior post. However, it made the following points:
1. There was very little gender difference in the absolute size of the corpus callosum.
2. As the size of the whole brain decreases, the size of the corpus callosum tends to remain the same.
3. Thus the size ratio of the corpus callosum to whole brain size is higher in smaller brains.
4. Woman generally have smaller brains than average-sized men, presumably because they have smaller heads and reduced cranial capacity.
5. Thus, most woman and smaller men have a larger corpus callosum relative to brain size.
This study would indicate that the size of the corpus callosum is not gender specific, but dependent only upon whole brain size.
* Cranial capacity does not equate to mental capacity. Any male who would disagree with this fact is, in fact, providing corroborative evidence of its validity.
- Scott
------------------------------------------------------------------9: J Neuropathol Exp Neurol 1999 Mar;58(3):217-26
The human cerebral cortex: gender differences in structure and function.
de Courten-Myers GM
Department of Pathology and Laboratory Medicine, University of Cincinnati, Ohio
45267-0529, USA.Most people are aware of subtle differences in cognitive functions between men and women. Psychometric tests confirm specific gender differences in a number of areas, the most robust being in spatial orientation and mathematical tasks which are better performed by males. Nonetheless, normal males and females perform comparably on intelligence tests and human brains lack sexual dimorphism on routine neuropathological exams--other than mean differences in weight and size. Even so, human brains demonstrate: 1) a sexually dimorphic nucleus in the hypothalamus with twofold neuronal numbers in males than in females; 2) the planum temporale/anterior Sylvian fissure on the left side are larger in males; 3) some studies reveal the posterior corpus callosum to be more bulbous in females while others fail to show this difference; and 4) a cytoarchitectural study demonstrates definite sexual dimorphism of cerebral cortex with significantly higher neuronal densities and neuronal number estimates in males and a reciprocal increase in neuropil/neuronal processes in female cortex as implied by the 2 sexes' similar mean cortical thicknesses. Such morphologic differences may provide the structural underpinning for the gender differences exhibited by the normal and diseased brain. Males manifest a higher prevalence of mental retardation and of learning disabilities than females which may reflect the male fetus' smaller overproduction of nerve cells. Such an inference is supported by the demonstration of 1) better functional recovery following early brain injury than after later insults, 2) substantially overproduced and secondarily reduced nerve cells in human cerebral cortex during gestation, 3) the demonstration of a similar neuronal production and a testosterone-dependent neuronal involution of the sexually dimorphic hypothalamic nucleus in rats, and 4) more cortical neurons present in the adult human male than female. If an overproduced nerve cell population is capable of compensating for pathologic nerve cell losses taking place during the process of neuronal involution, the magnitude of overproduced nerve cells may define the extent of the protection conveyed. Because male fetuses appear to involute fewer overproduced cortical neurons than females, this gender difference could explain in part the boys' greater functional impairments from early brain damage. Women, on the other hand, exhibit a higher incidence and prevalence of dementia than do men. Given the females' overall larger extent of cortical neuropil (neuronal processes) and lower neuronal numbers compared with men, any disease that causes neuronal loss could be expected to lead to more severe functional deficits in women due to their loss of more dendritic connections per neuron lost. In conclusion, superimposed on a strong background of functional and structural equality, human male and female cerebral cortex display distinct, sexually dimorphic features, which can begin to be linked to a complex array of gender-specific advantages and limitations in cognitive functions.
PMID: 10197813
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URL: http://www.dr-bob.org/babble/20010221/msgs/54639.html