Biomedical subjects

Richard G Schwartz

Publications and source records attributed to Richard G Schwartz.

8 recordsLinked to original sources

PubMed2006

Brain responses to filled gaps.

An unresolved issue in the study of sentence comprehension is whether the process of gap-filling is mediated by the construction of empty categories (traces), or whether the parser relates fillers directly to the associated verb's argument structure. We conducted an event-related potentials (ERP) study that used the violation paradigm to examine the time course and spatial distribution of brain responses to ungrammatically filled gaps. The results indicate that the earliest brain response to the violation is an early left anterior negativity (eLAN). This ERP indexes an early phase of pure syntactic structure building, temporally preceding ERPs that reflect semantic integration and argument structure satisfaction. The finding is interpreted as evidence that gap-filling is mediated by structurally predicted empty categories, rather than directly by argument structure operations.

Adult↗

PubMed2005

English past tense use in bilingual children with language impairment.

Grammatical measures that distinguish language differences from language disorders in bilingual children are scarce. This study examined English past tense morphology in sequential bilingual Spanish/English-speaking children, age 7;0-9;0 (years;months). Twelve bilingual children with language impairment (LI) or history of LI and 15 typically developing (TD) bilingual children participated. Thirty-six instances of the past tense including regular, irregular, and novel verbs were examined using an elicited production task. By examining English past tense morphology in sequential bilinguals, we uncovered similarities and differences in the error patterns of TD children and children with LI. The groups differed in the overall accuracy of past tense use according to verb type, as well as the characteristic error patterns. Children with LI performed lower than their TD peers on all verb categories, with an interaction between verb type and group. TD children were better at producing regular verbs and exhibited more productive errors (e.g., overregularization). Conversely, children with LI performed relatively better on irregular verbs and poorest on novel verbs, and they exhibited more nonproductive errors (e.g., bare stem verbs). The results have important clinical implications for the assessment of morphological productivity in Spanish-speaking children who are learning English sequentially.

Case-Control Studies↗

PubMed2005

Perception and production of lexical tones by 3-year-old, Mandarin-speaking children.

The present study investigated 3-year-old children's perception and production of Mandarin lexical tones in monosyllabic words. Thirteen 3-year-old, Mandarin-speaking children participated in the study. Tone perception was examined by a picture-pointing task, and tone production was investigated by picture naming. To compare children's productions with the adult forms, 4 mothers of the children were asked to say the same set of words to their children in a picture-reading activity. The children's and mothers' productions were low-pass filtered at 500 Hz and 400 Hz, respectively, to eliminate segmental information. Ten Mandarin-speaking judges identified the productions of tones from the filtered speech. Adult productions were more accurately identified than productions of the children. The children perceived the level, rising, and falling tones with relatively high accuracy. The dipping tone posed the greatest difficulty for the children in both perception and production.

Analysis of Variance↗

PubMed2005

Neurophysiological indexes of speech processing deficits in children with specific language impairment.

We used neurophysiological and behavioral measures to examine whether children with specific language impairment (SLI) have deficits in automatic processing of brief, phonetically similar vowels, and whether attention plays a role in such deficits. The neurophysiological measure mismatch negativity (MMN) was used as an index of discrimination in two tasks; one in which children ignored the auditory stimuli and watched a silent video and a second in which they attended to the auditory modality. Children with SLI showed good behavioral discrimination, but significantly poorer behavioral identification of the brief vowels than the children with typical language development (TLD). For the TLD children, two neurophysiological measures (MMN and a later negativity, LN) indexed discrimination of the vowels in both tasks. In contrast, only the LN was elicited in either task for the SLI group. We did not see a direct correspondence between the absence of MMN and poor behavioral performance in the children with SLI. This pattern of findings indicates that children with SLI have speech perception deficiencies, although the underlying cause may vary.

Acoustic Stimulation↗

PubMed2004

Electrophysiological indices of brain activity to "the" in discourse.

In a first experiment, we recorded event-related-potentials (ERPs) to "the" followed by meaningful words (Story) versus "the" followed by nonsense syllables (Nonse). Left and right lateral anterior positivities (LAPs) were seen from the onset of "the" up to 200 ms in both conditions. Later than 200 ms following the onset of "the", the left and right LAPs continued for "the" in the Story, but were replaced by a negativity in the Nonse Condition. In a second experiment, ERPs were recorded to "the" in the Story and Nonse contexts mixed together under two different task instructions (attend to the auditory stimuli versus ignore the auditory stimuli). The same pattern of findings as Experiment 1 were observed for the Story and Nonse contexts when the participants attended to the auditory stimuli. Ignoring the auditory stimuli led to an attenuation of the right LAP, supporting the hypothesis that it is an index of discourse processing.

Adult↗

PubMed2004

Language-specific memory traces of consonants in the brain.

This study examined whether experience with a native language affected processing of a place-of-articulation feature. In Experiment 1, 10 stimuli from a continuum of synthesized Hindi bilabial, dental and retroflexed stops were presented to English and Hindi speakers to examine discrimination and identification across the bilabial/dental and dental/retroflexed boundaries. In an oddball task designed to elicit mismatch negativity (MMN), subjects ignored these stimuli while their brain activity was recorded. All participants showed similar behavioral discrimination and identification. However, the English subjects were slower that the Hindi subjects on the discrimination task. All subjects were less accurate and slower at identifying and discriminating the dental and retroflexed compared to the bilabial sounds. A small MMN was observed for some of the bilabial-dental contrasts, but not for the dental-retroflexed contrasts. No group differences were found. In Experiment 2, MMN was observed to a greater stimulus difference (bilabial-retroflexed) and was earlier when the bilabial rather than the retroflexed sound served as the frequent stimulus for both groups. The MMN was also earlier for the Hindi than the English groups when the retroflexed sound served as the frequent stimulus. These results indicate that the Hindi speakers used detailed acoustic-phonetic information for more rapid brain discrimination than the English participants and that the dental-retroflexed discrimination is more difficult than the bilabial-dental discrimination for all speakers.

Acoustic Stimulation↗

PubMed2003

Working memory capacity and language processes in children with specific language impairment.

This study examined the interaction between working memory and language comprehension in children with specific language impairment (SLI), focusing on the function of the central executive component and its interaction with the phonological loop (A. D. Baddeley, 1986) in complex working memory tasks. Thirteen children with SLI and 13 age-matched (age range = 7;0 [years;months] to 10;0) children with typical language development participated. The tasks combined traditional nonword repetition tests and sentence comprehension by using sentences that differed in length and syntactic complexity. The children with SLI exhibited larger processing and attentional capacity limitations than their age-matched peers. Increased word length and syntactic complexity resulted in a large performance decrease in nonword repetition in both groups. There were some variations in the error pattern, which may indicate qualitative differences between the 2 groups. The performance of the children with SLI in nonword repetition, across the different tasks, indicated a limitation in simultaneous processing rather than difficulty in encoding and analyzing the phonological structure of the nonwords. Furthermore, syntactic complexity had a greater effect on performance accuracy than did sentence length.

Case-Control Studies↗

PubMedDate not supplied

Effect of sentence length and complexity on working memory performance in Hungarian children with specific language impairment (SLI): A cross-linguistic comparison.

BACKGROUND: English-speaking children with specific language impairment (SLI) perform more poorly than their typically developing peers in verbal working memory tasks where processing and storage are simultaneously required. Hungarian is a language with a relatively free word order and a rich agglutinative morphology. AIMS: To examine the effect of linguistic structure on working memory performance. It was examined whether syntactic complexity has a larger impact on working memory performance than sentence length in Hungarian-speaking children, similar to the findings in English speaking children. METHODS & PROCEDURES: In Experiment 1, performance accuracy was measured with two linguistic span tasks that included stimuli with varying sentence length and syntactic complexity. Experiment 2 examined the impact of sentence length and morphological complexity on working memory performance. OUTCOMES & RESULTS: Children with SLI performed more poorly than their age-matched peers in all working memory tasks. Their error patterns differed from those of children with typical language development. Children with SLI produced a high number of interference errors that indicate poor executive functions. The findings were compared with previous results of English-speaking children. Complexity affected working memory performance accuracy differently across languages. In English, it was the increase of syntactic complexity that resulted in a decrease in performance accuracy, whereas in Hungarian, it was the morphological complexity that had a large impact on working memory performance. CONCLUSIONS: Working memory performance depends on the linguistic characteristics of the language tested. In both English- and Hungarian-speaking children, complexity has a larger effect on verbal working memory performance than the length of the stimuli. However, complexity affects working memory performance accuracy differently across languages.

Analysis of Variance↗