Functional partitioning of sentence processing and emotional prosody in the right perisylvian cortex after perinatal stroke

In healthy adults different language abilities—sentence processing versus emotional prosody—are supported by the left (LH) versus the right hemisphere (RH), respectively. However, after LH stroke in infancy, RH regions often support both abilities with normal outcomes. This finding raises an important question: How does the functional map of RH regions change to support both emotional prosody and also typically left-lateralized language functions after an early LH stroke? Does sentence processing simply become reflected into RH frontotemporal regions and overlap with emotional prosody processing? Or do these functions overlap less than would be expected with simple mirroring? In the current work we used task fMRI to examine precisely how sentence processing and emotional prosody processing are both organized in the intact RH of individuals who suffered a large LH perinatal arterial ischemic stroke (LHPS participants). We evaluated the activation of two fMRI tasks that probed auditory sentence processing and emotional prosody processing, comparing the overlap for these two functions in the RH of individuals with perinatal stroke with the symmetry of these functions in the LH and RH of their healthy siblings. We found less activation overlap in the RH of individuals with LH perinatal stroke than would be expected if both functions retained their typical spatial layout, suggesting that their spatial segregation may be an important feature of a functioning language system.