The language environment to which children are exposed has an impact on later language abilities as well as on brain development; however, it is unclear how early such impacts emerge. This study investigates the effects of children's early language environment and socioeconomic status (SES) on brain structure in infancy at 6 and 30 months of age (both sexes included). We used magnetic resonance imaging to quantify concentrations of myelin in specific fiber tracts in the brain. Our central question was whether Language Environment Analysis (LENA) measures from in-home recording devices and SES measures of maternal education predicted myelin concentrations over the course of development. Results indicate that 30-month-old children exposed to larger amounts of in-home adult input showed more myelination in the white matter tracts most associated with language. Right hemisphere regions also show an association with SES, with older children from more highly educated mothers and exposed to more adult input, showing greater myelin concentrations in language-related areas. We discuss these results in relation to the current literature and implications for future research.

SIGNIFICANCE STATEMENT This is the first study to look at how brain myelination is impacted by language input and socioeconomic status early in development. We find robust relationships of both factors in language-related brain areas at 30 months of age.

孩子所处的语言环境对以后的语言能力以及大脑发育都有影响；然而，目前还不清楚这种影响多久会出现。本研究调查了儿童早期语言环境和社会经济地位 (SES) 对 6 个月和 30 个月婴儿期（包括男女）大脑结构的影响。我们使用磁共振成像来量化大脑特定纤维束中髓磷脂的浓度。我们的核心问题是，家庭录音设备的语言环境分析 (LENA) 测量和母亲教育的 SES 测量是否可以预测发育过程中的髓磷脂浓度。结果表明，接触大量家庭成人输入的 30 个月大的儿童在与语言最相关的白质束中表现出更多的髓鞘形成。右半球区域也显示出与社会经济地位的关联，年龄较大的孩子来自受过高等教育的母亲，接触更多的成人输入，在语言相关区域显示出更高的髓磷脂浓度。我们讨论这些结果与当前文献的关系以及对未来研究的影响。

意义声明这是第一项研究大脑髓鞘形成如何受到发育早期语言输入和社会经济地位影响的研究。我们发现 30 个月大时，这两个因素在与语言相关的大脑区域中存在牢固的关系。