Vita-Salute San Raffaele University and San Raffaele Scientific Institute, Milan, Italy.
Cortex. 2013 Mar;49(3):905-11. doi: 10.1016/j.cortex.2012.08.018. Epub 2012 Sep 1.
Language proficiency should modulate the regions involved in language control in predictable ways during language switching. However, prior studies reveal inconsistent effects on the regions involved in language monitoring [pre-Supplementary Motor Area/Anterior Cingulate Cortex (pre-SMA/ACC)] and language selection (left caudate) conceivably because variations in relative proficiency are confounded with other between-group differences. We circumvented this problem in an fMRI (functional Magnetic Resonance Imaging) study of overt picture naming in trilingual participants. In this case, the difference between a high-proficient and a low-proficient further language can be assessed within subjects with no between-group confound. We also used a monolingual group to assess the neural correlates of switching between two categories of response within the same language. We report a novel result: relative language proficiency dissociates response of the pre-SMA/ACC and left caudate during language switching. Switching between languages increased pre-SMA/ACC response regardless of proficiency differences. By contrast, left caudate response did vary with proficiency differences. Switching from the most to the least proficient language increased the response. Within-language switching, as contrasted with between-language switching, elicited a comparable increase in pre-SMA/ACC response but a decrease in left caudate response. Taken together, our data support a wider role of pre-SMA/ACC in task monitoring and establish the critical role of the left caudate in the selection of the less proficient language in language switching.
语言熟练度应该以可预测的方式调节语言切换过程中涉及的语言控制区域。然而，先前的研究揭示了对涉及语言监控[预备运动区/前扣带皮层（pre-SMA/ACC）]和语言选择（左尾状核）的区域的不一致影响，这可能是因为相对熟练度的变化与其他组间差异相混淆。我们在一项使用 fMRI（功能性磁共振成像）研究三种语言的显性图片命名的研究中解决了这个问题。在这种情况下，可以在没有组间混淆的情况下，在受试者内部评估高熟练和低熟练的进一步语言之间的差异。我们还使用单语组来评估在同一语言内两种反应类别之间切换的神经相关性。我们报告了一个新的结果：相对语言熟练度在语言切换过程中分离了 pre-SMA/ACC 和左尾状核的反应。无论熟练程度差异如何，语言之间的切换都会增加 pre-SMA/ACC 的反应。相比之下，左尾状核的反应确实因熟练程度的差异而变化。从最熟练的语言切换到最不熟练的语言会增加反应。与语言之间的切换相比，语言内切换会引起 pre-SMA/ACC 反应的可比增加，但左尾状核反应的减少。总之，我们的数据支持 pre-SMA/ACC 在任务监控中的更广泛作用，并确立了左尾状核在语言切换中选择不太熟练语言的关键作用。
