In studies of pitch processing, a fundamental question is whether shared neural mechanisms at higher cortical levels are engaged for pitch perception of linguistic and nonlinguistic auditory stimuli. Positron emission tomography (PET) was used in a crosslinguistic study to compare pitch processing in native speakers of two tone languages (that is, languages in which variations in pitch patterns are used to distinguish lexical meaning), Chinese and Thai, with those of English, a nontone language. Five subjects from each language group were scanned under three active tasks (tone, pitch, and consonant) that required focused-attention, speeded-response, auditory discrimination judgments, and one passive baseline as silence. Subjects were instructed to judge pitch patterns of Thai lexical tones in the tone condition; pitch patterns of nonspeech stimuli in the pitch condition; syllable-initial consonants in the consonant condition. Analysis was carried out by paired-image subtraction. When comparing the tone to the pitch task, only the Thai group showed significant activation in the left frontal operculum. Activation of the left frontal operculum in the Thai group suggests that phonological processing of suprasegmental as well as segmental units occurs in the vicinity of Broca's area. Baseline subtractions showed significant activation in the anterior insular region for the English and Chinese groups, but not Thai, providing further support for the existence of possibly two parallel, separate pathways projecting from the temporo-parietal to the frontal language area. More generally, these differential patterns of brain activation across language groups and tasks support the view that pitch patterns are processed at higher cortical levels in a top-down manner according to their linguistic function in a particular language.

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Grammatical inflections such as the English plural noun -s and third person singular verb -s are acquired at different points in time by young children. This finding is typically attributed to factors such as relative semantic salience or the distinction between lexical and functional categories. In this study input frequency, sentence position, and duration were examined as possible contributing factors. In both conversations with and stories aimed at young children, noun plural inflections were found to be more frequent than third singular verb inflections, especially in sentence-final position. Analysis of the speech of four mothers reading stories to their two-year-old children confirmed that duration differences also exist in the input. Because fricatives were lengthened in sentence-final position and plural nouns were much more likely to appear in these positions than were third singular verb forms, plural nouns were significantly longer than third singular inflections on average. The possible implications of these findings for language learnability theories and accounts of grammatical deficits in specific language impairment are discussed.