Rapid CommunicationSex differences in N-acetylaspartate correlates of general intelligence: An 1H-MRS study of normal human brain
Section snippets
Sample
Twenty-seven normal control subjects (17 male, 10 female) were recruited from the local college population (mean age = 24.8, SD = 5.89, range = 18–37). All control subjects were interviewed and screened by an experienced clinical neuropsychologist (RJ) and were free of any neurological, psychiatric, or developmental learning disorders. Four of the twenty-seven experimental subjects were left handed (3 male, 1 female).
Cognitive measures
All subjects completed the Wechsler Adult Intelligence Scale-III (Wechsler,
Results
Mean values for experimental variables stratified by sex are presented in Table 1. Males (N = 17) and females (N = 10) did not differ significantly in terms of age, handedness, or Full Scale IQ. Brain volume measures (all measures in cubic centimeters) differed significantly, with women having smaller volumes of pure WM [women = 523.19, men = 668.10, t(25) = −7.995, P < .001], pure GM [women = 560.29, men = 634.62, t(25) = −2.68, P = .013], and TBP [women = 1307.62, men = 1556.30, t(25) =
Discussion
The current findings raise several important issues regarding the biological mechanisms underlying human intelligence. With respect to volumetric measures, we found relatively modest correlations with FSIQ, similar to previous findings, and volumetric measures were not generally related to our biochemical measures. With respect to brain biochemistry, in a combined sample of men and women, we found that broad measures of intellectual and neuropsychological performance were related to NAA
Acknowledgments
We would like to thank Morris Baslow for his thoughtful insights and review of the manuscript. Portions of this research were presented at the 33rd annual meeting of the International Neuropsychological Society.
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