Developmental plasticity and language reorganization after pediatric stroke

It is well known that the adult human brain is highly lateralized for language, with the left hemisphere primarily responsible for sentence production and comprehension and the right hemisphere primarily responsible for suprasegmental aspects of language such as the expression of emotion and intonation. It has also long been hypothesized that there is a high degree of plasticity for language in early life, allowing young children to acquire language successfully by using other cortical regions for linguistic functions when the normal left hemisphere language areas are damaged. Are both of these claims true? If so, how do they fit together, and what are the principles and constraints on developmental plasticity and long-term functional organization? Which areas of the brain are capable of controlling language functions, and how well do they do this? If language is ‘reorganized’ to atypical regions, what happens to other cortical and cognitive functions?

We address these questions by focusing on long-term outcomes in a well-defined population of children with a single major injury at birth (perinatal arterial ischemic stroke to the middle cerebral artery). We study older children and young adults who have had a perinatal stroke to the left hemisphere brain areas ordinarily subserving language, or to the homologous right hemisphere areas ordinarily subserving the processing of emotion and spatial cognition. We are using a battery of behavioral tasks and fMRI to examine their processing and neural activation for language materials (sentence comprehension, emotional prosody) and for visual-spatial materials (line bisection, block configuration). We are also testing their healthy same-aged siblings and, in order to understand the early developmental status of these functions in the brain, a separate group of healthy children from ages 5 to 10. We believe that our results provide insights into both the striking lateralization of language functions in healthy adults and also the remarkable ability of the young brain to reorganize these functions in specific and highly constrained ways. 

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