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FROM FIRST WORDS TO GRAMMAR

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FROM FIRST WORDS TO GRAMMARIN CHILDREN WITH FOCAL BRAIN INJURYElizabeth BatesUniversity of California, San DiegoDonna ThalSan Diego State UniversityDoris TraunerUniversity of California, San DiegoJudi FensonChildren’s Hospital & Research Center, San DiegoDorothy AramEmerson CollegeJulie EiseleSkidmore CollegeRuth NassNew York University Medical CenterIn D. Thal & J. Reilly (Eds.), Special issue on Origins of Language Disorders.Developmental Neuropsychology, 1997, 13, 275-343.This research was supported by NIH/NIDCD Program Project P50 DC01289-0351“Origins of communicative disorders” to Elizabeth Bates, and by a grant from the John D.and Catherine T. MacArthur Foundation. We are grateful to Larry Juarez and Meiti Opiefor assistance in manuscript preparation.2ABSTRACTThe effects of focal brain injury are investigated in the first stages of language development,during the passage from first words to grammar. Parent report and/or free speech data arereported for 53 infants and preschool children between 10 - 44 months of age. All children hadsuffered a single, unilateral brain injury to the left or right hemisphere, incurred before sixmonths of age (usually in the pre- or perinatal period). This is the period in which we shouldexpect to see maximal plasticity, but it is also the period in which the initial specializations ofparticular cortical regions ought to be most evident. In direct contradiction of hypotheses basedon the adult aphasia literature, results from 10 - 17 months suggest that children with right-hemisphere injuries are at greater risk for delays in word comprehension, and in the gestures thatnormally precede and accompany language onset. Although there were no differences betweenleft- vs. right-hemisphere injury per se on expressive language, children whose lesions includethe left temporal lobe did show significantly greater delays in expressive vocabulary andgrammar throughout the period from 10 - 44 months. There were no specific deficits associatedwith left frontal damage, but there was a significant effect of frontal lobe injury to eitherhemisphere in the period from 16 - 31 months, when normal children usually show a burst invocabulary and grammar. This bilateral effect of frontal damage is independent of motorimpairment. Hence there are specific effects of lesion site in early language development, butthey are not consistent with the lesion-syndrome correlations observed in adults withhomologous injuries, nor with the literature on acquired lesions in older children. Results areused to argue against innate localization of linguistic representations, and in favor of analternative view in which innate regional biases in style of information processing lead tofamiliar patterns of brain organization for language under normal conditions, while permittingalternative patterns to emerge in children with focal brain injury.3FROM FIRST WORDS TO GRAMMARIN CHILDREN WITH FOCAL BRAIN INJURYIn 1861, Paul Broca described a case of nonfluent aphasia with preserved comprehension,associated with damage to a region of left frontal cortex that now bears Broca's name. By 1874,Carl Wernicke had described a very different form of aphasia, a severe comprehension deficitwith preserved fluency and melodic line (albeit with clear impairment of word retrieval). Thissyndrome was associated with damage to the posterior portion of the left temporal lobe, a regionnow referred to as Wernicke's area. The reliability and significance of these two complementarylesion-syndrome mappings have been called into question many times (Freud 1891/1953;Goldstein, 1948; Head, 1963; Marie, 1906; Mohr et al., 1978), including recent studies using invivo brain imaging which show that the classic lesion-syndrome correlations are violated at least20% of the time (Basso, Capitani, Laiacona, & Luzzatti, 1980; Bates, Appelbaum, & Allard,1991; Dronkers, Shapiro, Redfern, & Knight, 1992; Willmes & Poeck, 1993). Nevertheless,there is still broad consensus on four points.(1) The left hemisphere is specialized for language in over 95% of normal adults(Bryden, 1982; Damasio, 1992; Galaburda, 1994; Gazzaniga, 1994; Hellige, 1993).(2) The perisylvian regions of the left hemisphere are particularly important for language(Damasio, 1989; Damasio & Damasio, 1992; Geschwind, 1972; Rasmussen &Milner, 1977), although they are not the only relevant areas (Ojemann, 1991).(3) The contrasting syndromes described by Broca and Wernicke are robust findingsacross natural languages (Bates & Wulfeck, 1989; Menn & Obler, 1990).(4) These syndromes are reliably albeit imperfectly correlated with anterior vs. posteriorlesion sites along the Sylvian fissure (Damasio, 1992; Goodglass, 1993; Naeser,Helm-Estabrooks, Haas, Auerbach, & Levine, 1984)Given these findings in adults, it is not unreasonable to assume that the left hemispheremust be innately specialized for language, with privileged roles for the perisylvian areas that areimplicated in the major forms of aphasia. On these grounds, one would expect to find forms oflanguage impairment in small children with unilateral brain injury that are grossly analogous tothe major categories of aphasia in adults, an expectation that can be framed in terms of threehypotheses.4(1) The left-specialization hypothesis predicts more severe language impairmentsoverall in children with injuries to the left hemisphere.(2) The Broca hypothesis predicts more severe deficits in language production amongchildren with damage to the anterior regions of the left hemisphere (in particular, theperisylvian area of the left frontal lobe).(3) The Wernicke hypothesis predicts more severe deficits in language comprehensionin children with damage to the posterior regions of the left hemisphere (in particular,the posterior portion of the left temporal lobe).Although these adult-based hypotheses form a reasonable starting point fordevelopmental research, they are largely unsupported by the literature on language developmentin children with focal brain injury (Alajouanine & Lhermitte, 1965; Almli & Finger, 1984;Annet, 1973; Aram, 1988, 1992; Aram, Ekelman, & Whitaker, 1985, 1986; Aram, Meyers, &Ekelman, 1990; Bishop, 1981, 1983, 1992; Day & Ulatowska, 1979; Fletcher, 1993; Hammill &Irwin, 1966; Hecaen, 1976, 1983; Hecaen, Pernin, & Jeannerod, 1984; Isaacson, 1975; Janowsky& Finlay, 1983; Kohn, 1980; Kohn & Dennis, 1974; Marchman, Miller, & Bates, 1991; Reed &Reitan, 1969; Reilly, Bates, & Marchman, in


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