Magnitude comparisons by children with specific language impairments: evidence of unimpaired symbolic processing

Astrocytes possess plasma membrane glutamate transporters that rapidly remove glutamate from the extracellular milieu and thereby prevent excitotoxic injury to neurons. Cellular oxidative stress is increased in neural tissues in a variety of acute and chronic neurodegenerative conditions. Recent findings suggest that oxidative stress increases neuronal vulnerability to excitotoxicity and that membrane lipid peroxidation plays a key role in this process. We now report that 4-hydroxynonenal (HNE), an aldehydic product of membrane lipid peroxidation, impairs glutamate transport in cultured cortical astrocytes. Impairment of glutamate transport occurred within 1-3 h of exposure to HNE; FeSO4, an inducer of membrane lipid peroxidation, also impaired glutamate transport. Vitamin E prevented impairment of glutamate transport induced by FeSO4, but not that induced by HNE, consistent with HNE acting as an effector of lipid peroxidation-induced impairment of glutamate transport. Glutathione, which binds and thereby detoxifies HNE, prevented HNE from impairing glutamate transport. Western blot, immunoprecipitation, and immunocytochemical analyses using an antibody against HNE-protein conjugates provided evidence that HNE covalently binds to many different astrocytic proteins including the glutamate transporter GLT-1. Data further suggest that HNE promotes intermolecular cross-linking of GLT-1 monomers to form dimers. HNE also induced mitochondrial dysfunction and accumulation of peroxides in astrocytes. Impairment of glutamate transport and mitochondrial function occurred with sublethal concentrations of HNE, concentrations known to be generated in cells exposed to various oxidative insults. Collectively, our data suggest that HNE may be an important mediator of oxidative stress-induced impairment of astrocytic glutamate transport and may thereby play a role in promoting neuronal excitotoxicity.     

Causative alternations of children with specific language impairment

Alternating verbs to indicate or to relinquish cause requires an understanding of semantic and syntactic knowledge. This study evaluated the ability of children with specific language impairment (SLI) to produce the causative alternation in comparison to age peers and to language peers. The children with SLI were proficient in lexically alternating verbs, yet provided fewer passive and periphrastic constructions and more different verbs and adjectival responses. Overgeneralization error data suggest that the semantic systems of some children with SLI were similar to their age comparisons. Individual differences within the SLI group suggested that some children were adept at providing syntactic responses and overgeneralizations, whereas some of the SLI group provided less mature responses of no alternations and no responses. These findings demonstrate a syntactic deficit in the causative alternation for some children with SLI.     

Auditory lexical decisions of children with specific language impairment

To determine whether children with specific language impairment (SLI) take longer than age peers to recognize sequences of sounds that represent words in their lexicon, we compared auditory lexical decision times of children with SLI to those of typically developing age peers. Children with SLI were significantly slower than peers, but speed of word recognition was not correlated with measures of language comprehension for children with SLI. Furthermore, time to detect an auditory signal and initiate a vocal response did not account for the differences between groups. Possible interpretations of the results are discussed with two explanations-differences between groups in task-related factors that stressed processing capacity or in the nature of phonetic/phonological representations-seeming more likely than others.     

The effect of presentation rate on serial memory in young children with specific language impairment

The study examined the serial memory ability of a group of preschool children with specific language impairment (SLI) who were compared to age and language control groups. The children were asked to recognize serial patterns under short and long presentation durations. The subjects were presented with images of common objects (that appeared to be easily recoded into a phonological form) and iconic images of scribble drawings and unfamiliar faces (that did not appear to invite recoding). Under long presentation conditions, the performance of children with SLI resembled that of their age-matched peers on all 3 types of tasks. However, under short presentation conditions, children with SLI performed worse than their age-matched peers on all 3 tasks (and similarly to their language-matched peers). The performance of the children with SLI declined dramatically in all conditions when the items were presented for a brief period. If the serial memory deficits of young children with SLI were specific to phonological processing, their performance on recognizing the pattern of common objects should have been impaired, but not their performance with other visual tasks that are less likely to be recoded. Instead, serial memory in children with SLI was affected by presentation duration across tasks. The findings suggest that recognizing serial patterns is dependent, in part, on the speed of processing serial information. The findings are discussed in relation to models of limited capacity processing.     

Language in Italian children with Down syndrome and with specific language impairment.

This article compares lexical and grammatical abilities of a mental-age-matched sample of Italian preschoolers with Down syndrome (DS), specific language impairment (SLI), or typical development. Results showed that the children with DS or with SLI performed significantly worse than did the typically developing children. Although no significant differences emerged in lexical abilities and morphosyntactic comprehension abilities between the children with DS or with SLI, significant differences did emerge in morphosyntactic production capacities. Qualitative analysis of the morphosyntactic errors revealed strong similarities between the two groups. The results are discussed in terms of the role of verbal memory abilities and the linguistic features of Italian. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Uninflected structure in familial language impairment: evidence from French

We present the results of 20 French subjects with familial language impairment (FLI) on a linguistic battery task, with an emphasis on verb production. The results show strong qualitative differences between the verb production of FLI subjects and that of controls. Language-specific factors do not seem to determine the production of verbs in French FLI individuals. Rather, verb frequency and the inflectional status (uninflected vs. inflected) of the form seem to be determining factors in correct/incorrect production of a verb in a sentence context. The phonetic structure of French inflection provides additional arguments against the hypothesis of a processing deficit in FLI subjects. French tense morphemes are stressed and salient, and should therefore be produced without problems, according to the processing hypothesis. We found evidence contrary to this postulate. We therefore submit that the morphological deficit hypothesis is supported by the French data.     

Lexical learning by children with specific language impairment: effects of linguistic input presented at varying speaking rates

The purpose of this study was to investigate the impact of speaking rate variations in the linguistic input provided to children during a novel word learning task. Thirty-two school-age children participated in this investigation, including 16 children with specific language impairment (SLI) and 16 normal language (NL) controls matched on mental age (MA). The younger half of the NL group also served as a vocabulary level comparison for the older half of the children with SLI. No significant rate effects were found for comprehension of novel words, with all children performing at relatively high levels of accuracy. The group with SLI demonstrated the same recognition accuracy pattern as MA matched controls for target labels versus phonetically similar/dissimilar foils only for words trained at slow rate. Rate effects were most pronounced for items with the highest difficulty level, namely production of novel words. Children with SLI produced significantly fewer words that had been presented at fast rate during training than NL children matched on mental age or vocabulary level. Individual differences and production error patterns on fast rate items were examined. The finding that variations in speaking rate had a disproportionate impact upon word learning for children with SLI was interpreted within a framework of limited processing capacity.     

Toward tense as a clinical marker of specific language impairment in English-speaking children

A critical clinical issue is the identification of a clinical marker, a linguistic form or principle that can be shown to be characteristic of children with Specific Language Impairment (SLI). In this paper we evaluate, as candidate clinical markers, a set of morphemes that mark Tense. In English, this includes -s third person singular, -ed regular past, BE, and DO. According to the Extended Optional Infinitive Account (EOI) of Rice, Wexler, and Cleave (1995), this set of morphemes is likely to appear optionally in the grammars of children with SLI at a rate lower than the optionality evident in younger controls. Three groups of preschool children participated: 37 children with SLI, and two control groups, one of 40 MLU-equivalent children and another of 45 age-equivalent children. Three kinds of evidence support the conclusion that a set of morphemes that marks Tense can be considered a clinical marker: (a) low levels of accuracy for the target morphemes for the SLI group relative to either of the two control groups; (b) affectedness for the set of morphemes defined by the linguistic function of Tense, but not for morphemes unrelated to Tense; and (c) a bimodal distribution for Tense-marking morphemes relative to age peers, in which the typical children are at essentially adult levels of the grammar, whereas children in the SLI group were at low (i.e., non-adultlike) levels of performance. The clinical symptoms are evident in omissions of surface forms. Errors of subject-verb agreement and syntactic misuses are rare, showing that, as predicted, children in an EOI stage who are likely to mark Tense optionally at the same time know a great deal about the grammatical properties of finiteness and agreement in the adult grammar. The findings are discussed in terms of alternative accounts of the grammatical limitations of children with SLI and implications for clinical identification.     

Syllabic effects in word processing: evidence from the structural induction paradigm

Spoken words have a rich structural organization in memory, consisting of syllabic and subsyllabic representations. A phoneme monitoring paradigm, in which the target phoneme occurs more frequently in one syllabic position than another (e.g., onset of the 2nd syllable vs. the coda of the 1st syllable: neu-tral vs. nut-meg; C. Pallier, N. Sebastian-Galles, T. Felguera, A. Christophe, & J. Mehler, 1993) was used to explore the formation of syllabic structure during word processing. Experiment 2 investigated how a recognition system that uses syllabic structure processes words with unclear syllable boundaries (e.g., pa-lace or pal-ace?). Two methodological issues were explored: The importance of a baseline condition for measuring effects of induction (Experiment 1) and the form of the representation used in the induction paradigm (Experiment 3). Findings suggest that syllabic structure begins to form early in word processing, and they demonstrate the adequacy of the induction procedure for measuring such processes.     

Identifiers of predominantly Spanish-speaking children with language impairment

The purpose of this study was to identify a set of measures that would discriminate 31 predominantly Spanish-speaking children with normal language (NL children) from 31 children with language impairment (LI children). The LI children were identified as such by experienced, bilingual (Spanish/English), ASHA-certified, speech-language pathologists who were currently seeing the children in their caseloads. Children ranged in age from 5 to 7 years and were matched for age, gender, and school. Additionally, nonverbal cognitive measures assured that they did not differ significantly intellectually. Measures of vocabulary, novel bound-morpheme learning skills, and language form were randomly administered to all children. Further, parents responded to questions about their perceptions of their children's speech and language skills and family history of speech and language problems. A stepwise discriminant analysis indicated that 4 measures discriminated the groups of children with a sensitivity of 91.3% and a specificity of 100% (p < .0001): parental report of the child's speech and language skills, number of errors per T-unit, mean length per T-unit, and family history of speech and language problems. A second discriminant analysis indicated that the sensitivity and specificity could be maintained when only the first 2 measures were included. Confirmatory discriminant analyses of the 2- and 4-measure models indicated that the discriminant accuracy was stable on an independent sample.     

Auditory processing and dyslexia: evidence for a specific speech processing deficit

Following transection of a peripheral nerve in mice, a newly synthesized neurotropic pyrimidine compound, MS-818 was administered intraperitoneally at a dose of 1 mg kg-1 b.wt. day-1. The film model experiments for analyzing the early growth of axonal regeneration suggested that MS-818 activated Schwann cells which migrate from the proximal stump, inducing axonal elongation in vivo.     

Hierarchical planning abilities in children with specific language impairments

The present study examined Cromer's (1983) claim that children with language impairments have a hierarchical planning deficit that affects language as well as performance on complex construction tasks. Subjects were 30 boys (ages 5-7 years), 15 with specific language impairments (SLI) and 15 with normally developing language. Children were asked to build four hierarchical structures: a block construction, a puzzle construction, a simple straw construction, and a complex straw construction. Children who failed to complete the complex straw construction were taught how to construct the model using a sequential strategy. The two groups tended to perform comparably on the block and complex straw construction, the easiest and hardest of the four constructions. The two groups performed least comparably on the puzzle, simple straw construction, and the training task. On the basis of these findings and recent work by Greenfield (1991), we concluded that it is time to reject the notion that a central hierarchical planning mechanism underlies language and non-language structures that contain hierarchical components. The possible exception is early in development before language and manual actions become more autonomous and modular in nature.     

Factors related to English reading performance in children with Chinese as a first language: More evidence of cross-language transfer of phonological processing.

Parallel measures of phonological, syntactic, and orthographic processing skill and reading were administered in English and in Chinese to 65 children whose 1st language (L1) was Cantonese and whose 2nd language (L2) was English. Phonological skill was correlated across L1 and L2. Phonological skill in both L1 and L2 was correlated with L2 reading and contributed a unique variance to L2 reading, even though the children's L1 was not written in an alphabetic orthography, whereas the 2nd language had an alphabetic orthography. This research adds to a growing body of evidence for cross-language transfer of phonological processing in L2 learning of English-as-a-Second-Language students. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deficits in finite verb morphology: some assumptions in recent accounts of specific language impairment

Multiple aspartate-specific cysteine proteases have been identified and specific members of this family have been implicated in the apoptotic death of many mammalian cell types. Caspase-3-like proteases seem to play a pivotal role in neuronal apoptosis since mice with germline inactivation of the caspase-3 gene manifest profound alterations in neurogenesis. Moreover, inhibitors of caspase-3-related proteases have been shown to inhibit neuronal apoptosis. Here we extend recent work from our laboratory on the mechanisms mediating the neurotoxic actions of 1-methyl-4-phenylpyridinium using ventral mesencephalon cultures containing dopamine neurons. We demonstrate that low concentrations of 1-methyl-4-phenylpyridinium induce apoptosis in dopamine neurons by morphological and biochemical criteria. Moreover, pretreatment of ventral mesencephalon cultures with the tetrapeptide inhibitors of the caspase-3-like proteases zVAD-FMK or Ac-DEVD-CHO specifically inhibit death of dopamine neurons induced by low concentrations of 1-methyl-4-phenylpyridinium, whereas the caspase-1-like inhibitor Ac-YVAD-CHO was without effect. Our data indicate that exposure of cultured ventral mesencephalon dopamine neurons to low concentrations of 1-methyl-4-phenylpyridinium results in apoptotic death and that caspase-3-like proteases may mediate the neurotoxic apoptotic actions of 1-methyl-4-phenylpyridinium.     

Visual perception modifies goal-directed movement control: supporting evidence from a visual perturbation paradigm

It is well known that dynamic visual information influences movement control, whereas the role played by background visual information is still largely unknown. Evidence coming mainly from eye movement and manual tracking studies indicates that background visual information modifies motion perception and might influence movement control. The goal of the present study was to test this hypothesis. Subjects had to apply pressure on a strain gauge to displace in a single action a cursor shown on a video display and to immobilize it on a target shown on the same display. In some instances, the visual background against which the cursor moved was unexpectedly perturbed in a direction opposite to (Experiment 1), or in the same direction as (Experiment 2) the cursor controlled by the subject. The results of both experiments indicated that the introduction of a visual perturbation significantly affected aiming accuracy. These results suggest that background visual information is used to evaluate the velocity of the aiming cursor, and that this perceived velocity is fed back to the control system, which uses it for on-line corrections.     

Follow-up study of a right- and a left-hemispherectomized child: implications for localization and impairment of language in children

Two hemispherectomized girls, one operated on the right, the other on the left, were followed from time of surgery until 9 and 10 years of age and compared with respect to course of language acquisition following surgery. At conclusion of follow-up, receptive and expressive language, phoneme perception and production, and sentence processing of the two hemispherectomized children were compared with those of two control groups of similar age, one developing language normally, the other language-impaired. The left-hemispherectomized child's abilities were similar to those of the language-impaired children; the right-hemispherectomized child's abilities resembled those of the language-normal children. Implications for localization of developmental anomalies in language-impaired children are discussed.     

Information processing in Stroop-like picture naming tasks by preschool children

This study examined the difference between preschool (6-year-olds) children and adults in semantic information processing in line-drawn picture naming, using two types of Stroop-like picture naming tasks. In Experiment 1, voices (i.e., lexical information), and in Experiment 2, pictures (i.e., semantic information) were used as distracters. Subjects were asked to name target pictures as quickly as possible, ignoring distracters. To clarify the effect of semantic relations on the amount of interference, four types of target-distracter semantic relations were used as experimental conditions: same stimulus (SS), same category (SC), different category (DC), and control (C). To investigate the time course of processing, stimulus onset asynchrony (SOA) between target and distracter was varied. The results indicated that the patterns of reaction time showed more remarkable difference between children and adults in Experiment 1 than in Experiment 2. These results were discussed on the basis of Glaser and Glaser (1989)'s model in which semantic memory and lexicon were separate.     

Sensitivity to discontinuous dependencies in language learners: evidence for limitations in processing space

Five experiments using the Headturn Preference Procedure examined 15- and 18-month-old children's sensitivity to morphosyntactic dependencies in English. In each experiment, the children were exposed to two types of passages. Passages in the experimental condition contained a well-formed English dependency between the auxiliary verb is and a main verb with the ending -ing. Passages in the control condition contained an ungrammatical combination of the modal auxiliary can and a main verb with the ending -ing. In the experiments, the distance between the dependent morphemes was systematically varied by inserting an adverbial of a specified length between the auxiliary and main verbs. The results indicated that 18-month-olds are sensitive to the basic relationship between is and -ing, but that 15-month-olds are not. The 18-month-olds, but not the 15-month-olds, listened significantly longer to the passages with the well-formed English dependency. In addition, the 18-month-olds showed this preference for the well-formed dependency only over a limited domain of 1-3 syllables. Over domains of 4-5 syllables, they showed no significant preference for the experimental over the control passages. These findings indicate that 18-month-olds can track relationships between functor morphemes. Additionally, these findings are consistent with the hypothesis that 18-month-olds are working with a limited processing window, and that they are only picking up relevant dependencies that fall within this window.