The neural basis of emotional prosody processing: development of lateralization

In most healthy adults, core language functions (e.g. sentence processing) rely predominantly on the left hemisphere (LH), whereas emotional prosody processing (EP) relies predominantly on the right (RH). After LH injury, adults exhibit lasting impairments of sentence processing. In contrast, infants with similar injury can acquire processes typically subserved by the damaged LH by utilizing the homotopic regions of the intact RH. This suggests equipotentiality of the hemispheres and weaker lateralization early in life. Indeed, for sentence comprehension, neuroimaging reveals some degree of bilateral activation at younger ages that gradually shifts leftward over development. This study asks whether the complementary developmental process occurs for the processing of EP. Here we characterize the development of lateralization for EP in children ages 4-12 using fMRI. At the group level, we demonstrate bilateral fronto-temporal activation, though stronger on the right, consistent with prior results in adults. While strong right-lateralization is already evident in temporal cortex even in most of the youngest children, frontal lateralization is more variable and on average bilateral in the youngest children and becomes consistently right-lateralized only around age 8. These findings suggest that, like left-lateralization for sentence comprehension, the frontal right-lateralization of EP typical of the adult brain emerges gradually over development.