SEX DIFFERENCES IN BRAIN VOLUME OF INFANT RHESUS MACAQUES |
R. Hommer1; D. Rio2; R. Momenan2; P. Roma1; M. Champoux1; S. Higley1; J. Higley2; D. Hommer2 and S. Suomi1
1Lab. of Comparative Ethology, NICHD, NIHAC, Poolesville, MD, 20837, USA, 2Lab. of Clinical Studies, NIAAA, NIH |
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| It is well known that in humans males have larger brain volumes than do females and that this disparity appears early in life, long before large differences in body weight develop. Sex based differences in brain volume have been demonstrated in older juvenile and adult macaques, but no infant studies have been conducted. There is also considerable evidence that early life experiences can affect brain development in human and nonhuman primates. We measured the brain volumes of 14 infant rhesus macaques (Macaca mulatta): 7 males (3 peer-reared, 4 mother-reared) and 7 females (4 peer-reared, 3 mother-reared). Full, volumetric multiple echo images were collected using a 4.7 T scanner. Although males and females did not differ in body weight, males had significantly larger brain volumes than did females (males = 87.9 ± 7.7 ml; females = 73.5 ± 14.4 ml; t(12)=2.33; p<0.05). There was no significant difference in brain volume between mother- and peer-reared subjects. However, the two groups differed significantly in body weight. An ANCOVA co-varying for weight and age showed a trend for peer-reared monkeys to have smaller brains than mother-reared [F(1,8) = 4.45, p = 0.07]. Our results suggest that with regards to sex differences the brain growth pattern of rhesus macaques resembles that of humans. Further study is needed to illuminate a possible relationship between rearing condition and brain volume. |
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