Center for Brain Plasticity and Recovery, Georgetown University Medical Center, Georgetown University, Washington, DC 20057.
MedStar National Rehabilitation Hospital, Washington, DC 20010.
Proc Natl Acad Sci U S A. 2022 Oct 18;119(42):e2207293119. doi: 10.1073/pnas.2207293119. Epub 2022 Oct 10.
The mature human brain is lateralized for language, with the left hemisphere (LH) primarily responsible for sentence processing and the right hemisphere (RH) primarily responsible for processing suprasegmental aspects of language such as vocal emotion. However, it has long been hypothesized that in early life there is plasticity for language, allowing young children to acquire language in other cortical regions when LH areas are damaged. If true, what are the constraints on functional reorganization? Which areas of the brain can acquire language, and what happens to the functions these regions ordinarily perform? We address these questions by examining long-term outcomes in adolescents and young adults who, as infants, had a perinatal arterial ischemic stroke to the LH areas ordinarily subserving sentence processing. We compared them with their healthy age-matched siblings. All participants were tested on a battery of behavioral and functional imaging tasks. While stroke participants were impaired in some nonlinguistic cognitive abilities, their processing of sentences and of vocal emotion was normal and equal to that of their healthy siblings. In almost all, these abilities have both developed in the healthy RH. Our results provide insights into the remarkable ability of the young brain to reorganize language. Reorganization is highly constrained, with sentence processing almost always in the RH frontotemporal regions homotopic to their location in the healthy brain. This activation is somewhat segregated from RH emotion processing, suggesting that the two functions perform best when each has its own neural territory.
人类大脑在语言方面存在侧化现象，左半球（LH）主要负责句子处理，右半球（RH）主要负责处理语言的超音段方面，如声音情感。然而，长期以来人们一直假设，在生命早期，语言具有可塑性，当 LH 区域受损时，年幼的孩子可以在大脑的其他皮质区域获得语言。如果这是真的，那么功能重组的限制因素是什么？大脑的哪些区域可以获得语言，这些区域通常执行的功能会发生什么变化？我们通过检查在婴儿期因 LH 区域的围产期动脉缺血性中风而受损的青少年和年轻成年人的长期结果来回答这些问题。我们将他们与健康的同龄兄弟姐妹进行了比较。所有参与者都接受了一系列行为和功能成像任务的测试。尽管中风参与者在一些非语言认知能力方面存在障碍，但他们对句子和声音情感的处理与健康兄弟姐妹一样正常。在几乎所有情况下，这些能力在健康的 RH 中都得到了发展。我们的研究结果为人们理解年轻大脑非凡的语言重组能力提供了新的视角。重组受到高度限制，句子处理几乎总是发生在 RH 额颞叶区域，与健康大脑中的位置相对应。这种激活与 RH 情感处理有些分离，这表明这两种功能在各自拥有自己的神经区域时表现最佳。
