From first words to grammar in children with focal brain injury

Abstract

The 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 are reported for 53 infants and preschool children between 10 -44 months of age. All children had suffered a single, unilateral brain injury to the left or right hemisphere, incurred before six months of age (usually in the pre-or perinatal period). This is the period in which we should 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 -17 months suggest that children with righthemisphere 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-vs. right-hemisphere injury per se on expressive language, children whose lesions include the left temporal lobe did show significantly greater delays in expressive vocabulary and grammar throughout the period from 10 -44 months. There were no specific deficits associated with left frontal damage, but there was a significant effect of frontal lobe injury to either hemisphere in the period from 16 -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 not consistent 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, while permitting alternative patterns to emerge in children with focal brain injury. 3 FROM FIRST WORDS TO GRAMMAR IN 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 deficit with preserved fluency and melodic line (albeit with clear impairment of word retrieval). This syndrome was associated with damage to the posterior portion of the left temporal lobe, a region now referred to as Wernicke's area. The reliability and significance of these two complementary lesion-syndrome mappings have been called into question many times (Freud 1891(Freud /1953Goldstein, 1948;Head, 1963;Marie, 1906;Mohr et al., 1978), including recent studies using in vivo brain imaging which show that the classic lesion-syndrome correlations are violated at least 20% of the time (Basso, C...

Familiar words capture the attention of 11-month-olds in less than 250 ms

“…Such a lateralized effect supports the theory of early right-hemisphere involvement in language development [18] but stands in contrast to studies of phoneme discrimination, which have found early signs of left-greater-than-right asymmetries [1]. While left temporal brain structures are thought to be more involved in phonological decoding and phonological discrimination in both infants [1,19,20] and adults [15,21,22], it has been proposed that word-level recognition processes involve right-sided regions during the earliest stages of language acquisition [18,23,24].…”

Differential Effects of Unilateral Lesions on Language Production in Children and Adults

“…Although the lesion-symptom correlations that we observe do not always match the correlations observed in adults, they may provide insights into the initial conditions that lead to left-hemisphere specialization for language under normal conditions (Bates et al, 1997;Reilly et al, 1998;Thal et al, 1991;Vicari et al, 2000). For example, we find that early delays in word comprehension and symbolic gesture are actually somewhat more common in children with RHD, but this bias has only been observed in our laboratories in the period between 10 and 20 months of age.…”

“…Even more surprising from the point of view of adult aphasia, it has proven extremely difficult to demonstrate significant differences in language outcomes between children with left-hemisphere damage (LHD) vs right-hemisphere damage (RHD). Although some differences have been reported during the period in which language is first acquired (Bates et al, 1997;Reilly, Bates, & Marchman, 1998;Thal et al, 1991;Vicari et al, 2000), the vast majority of studies have failed to uncover robust and statistically reliable left/right differences in children who are tested beyond 5-7 years of age. To be sure, a few studies have reported subtle differences between LHD children and their controls, differences that are not observed (or occur in a less specific form) when RHD children are compared to their own, separate group of controls Aram, Ekelman, Rose, & Whitaker, 1985;Ballantyne, Scarvie, & Trauner, 1994-but see Ballantyne & Trauner, 1999;Dennis & Whitaker, 1976Riva, Cazzaniga, Pantaleoni, Milani, & Fedrizzi, 1986).…”

Language Development in Sub-Saharan Africa

“…Language development is also arguably one of the most rapid aspects of development, and shows great variability between children (Bates, Dale, & Thal, 1995;Fenson et al, 2000;Fenson, Dale, Reznick, & Bates, 1994), as well as being sensitive to a number of negative factors that are more common in this setting, including HIV infection, cerebral malaria, meningitis, and other causes of brain injury and dysfunction (Baker, Kummer, Schultz, & Ho, 1996;Bates et al, 1997;Brouwers et al, 2001;Davis et al, 1997;McNeilly, 2005;Wolters, Brouwers, Civitello, & Moss, 1997). Its study therefore has become in recent years an essential part of studies of child development outcomes following exposures and interventions in the prenatal period and infancy (A. Abubakar, Van Baar, Prado et al, 2010;Stoltzfus et al, 2001).…”