HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Pennington, B. F. Articles by DeFries, J. C. Search for Related Content PubMed PubMed Citation Articles by Pennington, B. F. Articles by DeFries, J. C.

A Twin MRI Study of Size Variations in the Human Brain

^a University of Denver
^b University of California-Irvine
^c Harvard Medical School
^d University of Colorado
^e Denver Veterans Affairs Medical Center

Although it is well known that there is considerable variation among individuals in the size of the human brain, the etiology of less extreme individual differences in brain size is largely unknown. We present here data from the first large twin sample (N=132 individuals) in which the size of brain structures has been measured. As part of an ongoing project examining the brain correlates of reading disability (RD), whole brain morphometric analyses of structural magnetic response image (MRI) scans were performed on a sample of adolescent twins. Specifically, there were 25 monozygotic (MZ) and 23 dizygotic (DZ) pairs in which at least one member of each pair had RD and 9 MZ and 9 DZ pairs in which neither member had RD.

We first factor-analyzed volume data for 13 individual brain structures, comprising all of the neocortex and most of the subcortex. This analysis yielded two factors ("cortical" and "subcortical") that accounted for 64% of the variance.

We next tested whether genetic and environmental influences on brain size variations varied for these two factors or by hemisphere. We computed intraclass correlations within MZ and DZ pairs in each sample for the cortical and subcortical factor scores, for left and right neocortex, and for the total cerebral volume.

All five MZ correlations were substantial (r's=.78 to .98) and significant in both samples, as well as being larger than the corresponding DZ correlations, (r's=0.32 to 0.65) in both samples. The MZ-DZ difference was significant for 3 variables in the RD sample and for one variable in the smaller control sample. These results indicate significant genetic influences on these variables. The magnitude of genetic influence did not vary markedly either for the 2 factors or the 2 hemispheres.

There was also a positive correlation between brain size and full-scale IQ, consistent with the results of earlier studies. The total cerebral volume was moderately correlated (r=.42, p<.01, two-tailed) with full-scale IQ in the RD sample; there was a similar trend in the smaller control sample (r=.31, p<.07, two-tailed). Corrections of similar magnitude were found between the subcortical factor and full-scale IQ, whereas the results for the cortical factor (r=.16 and .13) were smaller and not significant.

In sum, these results provide evidence for the heritability of individual differences in brain size which do not vary markedly by hemisphere or for neocortex relative to subcortex. Since there are also correlations between brain size and full-scale IQ in this sample, it is possible that genetic influences on brain size partly contribute to individual differences in IQ.

This article has been cited by other articles:

				J.-F. Demonet, G. Thierry, and D. Cardebat Renewal of the Neurophysiology of Language: Functional Neuroimaging Physiol Rev, January 1, 2005; 85(1): 49 - 95. [Abstract] [Full Text] [PDF]

				M. Kaschube, F. Wolf, T. Geisel, and S. Lowel Genetic Influence on Quantitative Features of Neocortical Architecture J. Neurosci., August 15, 2002; 22(16): 7206 - 7217. [Abstract] [Full Text] [PDF]

				E. H. Aylward, N. J. Minshew, K. Field, B. F. Sparks, and N. Singh Effects of age on brain volume and head circumference in autism Neurology, July 23, 2002; 59(2): 175 - 183. [Abstract] [Full Text] [PDF]

				M. A. Eckert, C. M. Leonard, E. A. Molloy, J. Blumenthal, A. Zijdenbos, and J. N. Giedd The Epigenesis of Planum Temporale Asymmetry in Twins Cereb Cortex, July 1, 2002; 12(7): 749 - 755. [Abstract] [Full Text] [PDF]

				T. White, N. C. Andreasen, and P. Nopoulos Brain Volumes and Surface Morphology in Monozygotic Twins Cereb Cortex, May 1, 2002; 12(5): 486 - 493. [Abstract] [Full Text] [PDF]

				D. H. Geschwind, B. L. Miller, C. DeCarli, and D. Carmelli Heritability of lobar brain volumes in twins supports genetic models of cerebral laterality and handedness PNAS, February 20, 2002; (2002) 52494999. [Abstract] [Full Text] [PDF]

				H. E. Hulshoff Pol, D. Posthuma, W. F. C. Baare, E. J. C. De Geus, H. G. Schnack, N. E. M. van Haren, C. J. van Oel, R. S. Kahn, and D. I. Boomsma Twin-singleton differences in brain structure using structural equation modelling Brain, February 1, 2002; 125(2): 384 - 390. [Abstract] [Full Text] [PDF]

				D. M. Lyons, C. Yang, A. M. Sawyer-Glover, M. E. Moseley, and A. F. Schatzberg Early Life Stress and Inherited Variation in Monkey Hippocampal Volumes Arch Gen Psychiatry, December 1, 2001; 58(12): 1145 - 1151. [Abstract] [Full Text] [PDF]

				W. F.C. Baare, H. E. Hulshoff Pol, D. I. Boomsma, D. Posthuma, E. J.C. de Geus, H. G. Schnack, N. E.M. van Haren, C. J. van Oel, and R. S. Kahn Quantitative Genetic Modeling of Variation in Human Brain Morphology Cereb Cortex, September 1, 2001; 11(9): 816 - 824. [Abstract] [Full Text] [PDF]

				D. H. Geschwind, B. L. Miller, C. DeCarli, and D. Carmelli Heritability of lobar brain volumes in twins supports genetic models of cerebral laterality and handedness PNAS, March 5, 2002; 99(5): 3176 - 3181. [Abstract] [Full Text] [PDF]