ABSTRACT
The effects of focal brain injury were investigated in the first stages of language development, during the passage from first words to grammar. Parent report, free-speech data, or both are reported for 53 infants and preschool children between 10 and 44 months of age. All children had suffered a single, unilateral brain injury to the left or right hemisphere, incurred before 6 months of age (usually in the pre- or perinatal period). This is the period in which one would expect to see maximal plasticity, but it is also the period in which the initial specializations of particular cortical regions ought to be most evident. In direct contradiction of hypotheses based on the adult aphasia literature, results from 10 to 17 months suggest that children with right-hemisphere injuries are at greater risk for delays in word comprehension and in the gestures that normally precede and accompany language onset. Although there were no differences between left- and right-hemisphere injury per se on expressive language, children whose lesions included the left-temporal lobe showed significantly greater delays in expressive vocabulary and grammar throughout the period from 10 to 44 months. No specific deficits were associated with left-frontal damage, but there was a significant effect of frontal lobe injury to either hemisphere in the period from 16 to 31 months, when normal children usually show a burst in vocabulary and grammar. This bilateral effect of frontal damage is independent of motor impairment. Hence, there are specific effects of lesion site in early language development, but they are consistent neither with the lesion-syndrome correlations observed in adults with homologous injuries nor with the literature on acquired lesions in older children. Results are used to argue against innate localization of linguistic representations, and in favor of an alternative view in which innate regional biases in style of information processing lead to familiar patterns of brain organization for language under normal conditions and permit alternative patterns to emerge in children with focal brain injury.
