Regular articleEffects of gender on blood flow correlates of naming concrete entities
Introduction
There is considerable variability in the anatomic correlates of language among individuals, even in the degree to which they are lateralized to the left hemisphere Ojemann, 1979, Vikingstad et al., 2000. Much of the variability can be accounted for by individual Russell and Espir, 1961, LeCours et al., 1983, Milner, 1974, Penfield and Roberts, 1959, Luria, 1970 and familial (Luria, 1947; Bryden et al., 1983) handedness. The focus of this report is whether there are also systematic effects of gender on the neural support for aspects of language, as has been hinted at by reports of differential rates of language disorders in men and women after brain damage McGlone, 1977, Inglis and Lawson, 1981. Addressing this question requires confronting the problems of interindividual differences in the support of language, general anatomic sexual dimorphism of the brain, and the consistent performance advantages displayed by females in language tasks Halpern, 1992, Hyde and Linn, 1988; Bradshaw, 1989; Capitani et al., 1998).
Functional imaging to date has generated some evidence that there are gender differences in the physiologic correlates of the performance of a variety of language tasks, including grammatical, lexical semantic, and passive speech comprehension tasks Shaywitz et al., 1995, Pugh et al., 1996, Philips et al., 2001, Kansaku et al., 2000, Jaeger et al., 1998, Rossell et al., 2002. Several authors have commented on an apparent dependence of gender effects on the specific demands of language tasks, but consistent principles explaining the differences have not yet been identified. For example, Jaeger et al. (1998) suggested that greater left lateralization occurs for “grammatical or lexical tasks which require in-depth linguistic processing.” In contrast, Kansaku and Kitazawa (2001) proposed the following distinctions: sublexical processing is more left frontal lateralized in men, lexical processing is evenly lateralized, and passive listening to “global structure” is left temporal lateralized in men. However, neither account explains the results of Pugh et al., who found gender differences in a variety of language tasks at the single word level. More data need to be brought to bear using other language paradigms and paradigms tapping other domains of cognition Berman et al., 2000, Thomsen et al., 2000 before these issues can be resolved.
Naming to visual confrontation is one appealing paradigm, given that there is convergent evidence from lesion and functional imaging studies linking the retrieval of words denoting concrete entities to the left inferotemporal, temporal polar, and frontal cortex Bookheimer et al., 1995, Damasio and Damasio, 1992, Martin et al., 1996, Damasio et al., 1996, in press; for review, see Forde and Humphreys, 2002). We pooled data from a series of PET experiments involving naming concrete entities to investigate whether the physiologic correlates of naming differ systematically between men and women.
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Subjects
Subjects used for this experiment had been originally studied in five cohorts of normal subjects in five different experiments Damasio et al., 1996, Grabowski et al., 1998a; Damasio et al., 2001, Damasio, et al., in which word retrieval for one or more categories of nonunique concrete entities was performed during H215O-labeled (positron emission tomography) PET (Table 1). All subjects gave informed consent in accordance with institutional and federal guidelines.
For this analysis, we selected
Visual naming tasks
The naming performance success rate across all subjects was 93.6% (7.0%). Overall success for female subjects was 92.9% (8.3) and for male subjects was 94.3% (4.5). The difference was not significant (t104 = 1.07, P = n.s.; d = 0.21). The accuracy data were also analyzed with multiple linear regression, with effects of task and gender. There was no significant effect of task (F(3,97) = 1.27, P = n.s) or gender (t97 = 0.23, P = n.s.) and no significant interaction of task and gender (F(3,97) =
Discussion
Our study identified significant effects of gender on the physiologic correlates of naming visually presented concrete entities, despite being conservative in many respects. The most salient differences were greater activity in men in the left inferotemporal cortex and greater activity in women in the right hemisphere homologue of Broca's area. The conjunction analysis suggested that other left hemisphere regions are also more active in men than women, including parts of the left inferior
Conclusions
We found that there are gender differences in the physiologic correlates of visual naming. Men engage the left inferior temporal lobe more strongly than women during the retrieval of words denoting concrete entities. The data suggest that the difference is not limited to the left inferotemporal region, but also affects other sectors of the left frontal and right temporal lobes. Women engage the right frontal lobe more than men or deactivate it less than men. The results give new empirical
Acknowledgements
We are grateful to Sonya Mehta for careful and critical review of the manuscript and for helpful suggestions. This work was supported by NIDCD Grant 03189.
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