Department of Biological and Medical Psychology, University of Bergen, Norway.
Cortex. 2013 Jul-Aug;49(7):1910-21. doi: 10.1016/j.cortex.2012.08.002. Epub 2012 Aug 18.
Men are often believed to have a functionally more asymmetrical brain organization than women, but the empirical evidence for sex differences in lateralization is unclear to date. Over the years we have collected data from a vast number of participants using the same consonant-vowel dichotic listening task, a reliable marker for language lateralization. One dataset comprised behavioral data from 1782 participants (885 females, 125 non-right-handers), who were divided in four age groups (children <10 yrs, adolescents = 10-15 yrs, younger adults = 16-49 yrs, and older adults >50 yrs). In addition, we had behavioral and functional imaging (fMRI) data from another 104 younger adults (49 females, aged 18-45 yrs), who completed the same dichotic listening task in a 3T scanner. This database allowed us to comprehensively test whether there is a sex difference in functional language lateralization. Across all participants and in both datasets a right ear advantage (REA) emerged, reflecting left-hemispheric language lateralization. Accordingly, the fMRI data revealed a leftward asymmetry in superior temporal lobe language processing areas. In the N = 1782 dataset no main effect of sex but a significant sex by age interaction emerged: the REA increased with age in both sexes but as a result of an earlier onset in females the REA was stronger in female than male adolescents. In turn, male younger adults showed greater asymmetry than female younger adults (accounting for <1% of variance). There were no sex differences in children and older adults. The males in the fMRI dataset (N = 104) also had a greater REA than females (accounting for 4% of variance), but no sex difference emerged in the neuroimaging data. Handedness did not affect these findings. Taken together, our findings suggest that sex differences in language lateralization as assessed with dichotic listening exist, but they are (a) not necessarily reflected in fMRI data, (b) age-dependent and (c) relatively small.
男性的大脑组织在功能上通常被认为比女性更不对称，但迄今为止，关于性别的偏侧化差异的经验证据还不清楚。多年来，我们使用相同的辅音-元音双听任务（语言偏侧化的可靠标志物）从大量参与者那里收集数据。一项数据集包含来自 1782 名参与者（885 名女性，125 名非右利手者）的行为数据，这些参与者分为四个年龄组（儿童<10 岁，青少年=10-15 岁，年轻成年人=16-49 岁，老年人>50 岁）。此外，我们还有来自另外 104 名年轻成年人（49 名女性，年龄 18-45 岁）的行为和功能成像（fMRI）数据，他们在 3T 扫描仪中完成了相同的双听任务。该数据库使我们能够全面测试功能语言偏侧化是否存在性别差异。在所有参与者和两个数据集上，均出现右耳优势（REA），反映了左半球的语言偏侧化。相应地，fMRI 数据显示在颞上语言处理区域存在左偏侧性。在 N=1782 的数据集中，没有出现性别主效应，但出现了性别与年龄的显著交互作用：在两性中，REA 随年龄增长而增加，但由于女性的起始时间更早，女性青少年的 REA 强于男性青少年。相反，男性年轻成年人的不对称性大于女性年轻成年人（占方差的<1%）。在儿童和老年人中没有性别差异。fMRI 数据集（N=104）中的男性的 REA 也大于女性（占方差的 4%），但在神经影像学数据中没有出现性别差异。利手性不影响这些发现。综上所述，我们的研究结果表明，双听测试评估的语言偏侧化的性别差异存在，但（a）它们不一定反映在 fMRI 数据中，（b）依赖于年龄，并且（c）相对较小。
