PNAS：说两种语言或可引起大脑变化

在语言形成过程中，大脑会发出信号，可以观察到能说两种语言的人，与语言和认知处理有关的大脑活动可能会发生变化。

近日，刊登在《美国科学院院刊》（PNAS）的研究报告指出，与只能讲一种语言的人相比，能说两种语言的人的大脑皮层区域会产生功能性和结构性变化，这可能来源于其对语言的加工和执行。科研人员已经确定了会讲两种语言可能带来与语言和认知处理有关的大脑活动的变化。

正如玩戏法的人的大脑其与储存和处理复杂视觉运动有关的区域可能会出结构的变化一样，西北大学神经系统研究所的Nina Kraus及其同事们推测，由实践驱动的声音处理能力引起的大脑变化在能讲两种语言的人的大脑中或许是可识别的。为了寻找这类变化，该实验小组征召了芝加哥的48名中学生，其中大约一半人只讲英语，而另一半既讲英语又讲西班牙语。

研究人员将这些志愿者进行了分组，每个组都有数量大致相同的男性和女性。当他们看一部电影的时候，研究人员使用电生理技术测量了每一名志愿者的大脑对于记录一个合成语音音节的能力——这个音节既被单独播放，又放到了经录制的乱哄哄的人类语音背景中播放。研究结果显示，与只能说一种语言的人相比，能说两种语言的人表现出了增强这个音节基频的相关大脑皮层活动，特别是在这个声音放在乱哄哄的语音背景中播放的时候。研究者表示，这些发现提示能说两种语言的人可能拥有维持选择性注意力和增强听觉分类的能力。

doi:10.1073/pnas.1201575109
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Subcortical encoding of sound is enhanced in bilinguals and relates to executive function advantages

ennifer Krizman, Viorica Marian, Anthony Shook, Erika Skoe, and Nina Krausa

Bilingualism profoundly affects the brain, yielding functional and structural changes in cortical regions dedicated to language processing and executive function [Crinion J, et al. (2006) Science 312:1537–1540; Kim KHS, et al. (1997) Nature 388:171–174]. Comparatively, musical training, another type of sensory enrichment, translates to expertise in cognitive processing and refined biological processing of sound in both cortical and subcortical structures. Therefore, we asked whether bilingualism can also promote experience-dependent plasticity in subcortical auditory processing. We found that adolescent bilinguals, listening to the speech syllable [da], encoded the stimulus more robustly than age-matched monolinguals. Specifically, bilinguals showed enhanced encoding of the fundamental frequency, a feature known to underlie pitch perception and grouping of auditory objects. This enhancement was associated with executive function advantages. Thus, through experience-related tuning of attention, the bilingual auditory system becomes highly efficient in automatically processing sound. This study provides biological evidence for system-wide neural plasticity in auditory experts that facilitates a tight coupling of sensory and cognitive functions.