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  » Disorders related to Intelligence

  »  Gender Differences
       Self-Estimated              Intelligence
       Anatomical Differences
       Gray vs. White Matter

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  » Age and Intelligence
        Areas of Function
        Effects of Lesions

  » References

Gray Matter vs. White Matter

Within the brain, areas dominated by cell bodies are called gray matter because of their grayish appearance (surprising). While areas that are dominated by axons are called white matter, due to the whiteness caused by the myelin sheath that cover the axons.

One of the most studied aspects of intelligence now is the role of gray matter and white matter. Specifically speaking the location of gray matter (GM) and white matter (WM) in the brain and how its concentrations significantly differ between genders. It has been shown that GM volume is significantly correlated to FSIQ (considered one of the best indexes of individual differences in general intelligence). Specifically, in men it was most highly correlated in the bilateral frontal lobes (BA 8,9) and in the left parietal lobe; Wenicke’s area (BA 39 and 40). GM in men seemed to be evenly distributed in men, but in women it was found almost completely in the frontal lobe (84%). This is very interesting, because in men 0% of GM voxels were found in the frontal lobe. Another interesting fact is that men had 6.5 times the number of GM voxels that were identified as being related to intellectual functioning then men had. WM volume correlations did not report as strong of correlations with intelligence in men as they did in women. And again major sex differences were found in concentrations of WM. 86% of WM voxels for women were found in the frontal love, compared to 0% in men again. It was also found that the GM/WM matter ratio is slightly higher in women then in men. Other regions that women have larger concentrations of GM include the precentral gyrus, fronto-orbital cortex, superior frontal, and lingual gyri. Men had larger concentrations in the frontomedial cortex, hypothalamus, amygdala, and angular gyrus.

Women’s verbal intelligence was correlated to Broca’s area in women and Weirnke’s area in men. Broca’s area is involved in the motor production of speech, while Weirnke’s area is involved in the understanding of speech. The author does not go as far as drawing conclusions based on this information but it is interesting to think of how these differences could be influencing the differences in outwards language of male and females. Another implication that is not discussed is the considerable difference of GM and WM in the frontal lobe. Women contained 84% and 86% of voxels respectively, while men had 0%. The frontal lobe is considered to have a role in emotional control, personality, problem solving, motor function, memory, language, judgment, and social and sexual behavior.

The major result taken from this data is the importance of WM and GM intelligence in the striking differences between amount of voxels and location of these voxels between the sexes. Taking into account the fact that males and females do not differ in FSIQ the researchers concluded that different types of brain designs might change the “way” intelligence is derived but the overall performance is the same.


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