Language comprehension and cerebral specialization from 13 to 20 months

The purpose of this study was to examine developmental changes in the organization of brain activity linked to comprehension of single words in 13- to 20-month-old infants. Event-related potentials (ERPs) were recorded as children listened to a series of words whose meanings were understood by the child, words whose meanings the child did not understand, and backward words. The results were consistent with a previous study suggesting that ERPs differed as a function of word meaning within 200 ms after word onset. At 13 to 17 months, ERP differences between comprehended and unknown words were bilateral and broadly distributed over anterior and posterior regions. In contrast, at 20 months of age these effects were limited to temporal and parietal regions of the left hemisphere. The results are discussed in relation to the general effects of maturation, the maturation of language-relevant brain systems, and the development of brain systems linked to level of ability independent of chronological age. We offer the working hypothesis that the neurophysiological changes that give rise to certain ERP effects reported here are linked to the remarkable changes in early lexical development that typically occur between 13 and 20 months, whereas others produce more general maturational effects.