NemoImage 13, Number 6, 2001, Part 2 of 2 Parts 1 D E al@

PHYSIOLOGY

Gender differences in GM brain morphology: Voxel Based Morphometry in 92 healthy young women and men

Christian Kaufmann, Benno Puetz, Marko Wilke, Dorothee P. Auer

Sexual dimorphism in brain size and differences in cognitive functions are known for years but several questions regarding regional specific brain morphology and functional relevance remain unclear. Recently, Nopoulos [l] showed sex differences with proportionately more gray matter within the right parietal lobes in women. Gur [2] demonstrated a higher percentage of GM in women, and a higher percentage of WM and of CSF in men. Differences in the performance of cognitive tasks are well known, e.g. visuo-spatial tasks are better performed by men, and language tasks better by women [3]. Previously we observed gender differences in visual cortical BOLD responses [4]. Since women have more grey matter in right parietal areas, supposed to be relevant for visuo-spatial tasks, we evaluated wether other functional differences might also be reflected by morphometric gender differences. Here, we present voxel based morphometry (VBM) with SPM99 [5].

Methods

42 female and 50 male subjects were included in the study (age f:27t4,m:26?4.4,range:19-35). Data acquisition was done on a GE Signa Echospeed 1.5T clinical scanner. High resolution, sagittal, whole brain Tl-weighted spoiled gradient echo-datasets (SPGR, IR-PREPPED, TR= 10:3ms, TE=3.4ms; FOV=23x23cm, 256x256 matrix, flip angle=20”) were obtained yielding 124 contiguous slices with variable slice thickness (0.9-1.4mm) according to brain size. All af the automated image processing was done using SPM99 [6] as recommended [5]. The images were smoothed with a Gaussian kernel (FWHM) of 12 mm. Images were analyzed using a group comparison with age, a global intensitiy correction factor, and absolute, individual GM used as covariates. Significance level was set at p<O.OOl, k=50 pixels.

Results

As expected, cranial volume was larger in men than in women (1.4 vs. 1.24 1). Women had more GM in the Posterior Lobe (Cerebellum), Occipital Lobe, Left and Right Inferior Parietal Lobule, left and right temporal areas, the Left and Right Putamen, and Middle and Inferior Frontal Gyms (Fig. l), thus revealing wide- spread GM increases. Men did not show pronounced GM increases but a tendency for more GM in parietal (Cingulate Gyms) and frontal regions (Medial Frontal Gym).

Female > Male

Discussion

Our results reveal gender differences in brain morphology partially in line with previous studies [ 1,2]. Additionally we found differences in occipito-temporal and frontal lobes with females having more GM on both hemispheres. Women’s GM difference in the Putamen may reflect previously reported larger basal ganglia in women compared with men [7]. Women also showed more GM in the striate

Fig. 1: SPM glassbrain, neurological orien- tation (p<O.OOl, not corrected, thresholded at 50 voxels)

visual cortex where we recently found higher BOLD amplitudes in men compared with women. Thus, our results point at a negative correlation of BOLD amplitude and GM volume in this region. Further studies combining neuropsychological assessment and brain morphometry are needed to understand the functional significance of sexual dimorphism.

References

[l] Nopoulos P, Psych Res, 2000, 981-13 [2] Gur R, J Neuroscience, 1999, 155:785-94 [3] Kimura D, Curr Op Neurobiol, 1996, 6:259-263 [4] Kaufmann C, NI, 2000,11, 5:S737 [5] Ashbumer J, NI, 2000,ll: 805-21 [6] Friston K, HBM, 1995, 2:189-210 [7] Giedd JN, Prog Neuro-Psychopharm & Biol Psych, 1997, 21:1185-1201

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