Search

In this study we investigated lateralized control of speech during the intracarotid amobarbital procedure. Vowel segments were extracted from recordings made during two separate amobarbital procedures and involving two patients. Subjects were right-handed, presented with focal left mesial temporal epileptogenic foci. Age of onset of seizure disorders was 1.5 years for one subject and 16 years for the other. Recorded pre- and postinjection speech samples were digitized. Analyses were conducted on formants 1 and 2 (F1, F2) measures to determine the extent of formant fluctuation in the time course of the IAP. Preliminary results showed, for these two cases, that the left hemisphere is involved in the control of both F1and F2and the right in the control of F2only. The data reveal the potential of coupling the IAP procedure and the acoustical analysis of speech in the study of cerebral control of speech.

This study was concerned with the involvement of the cerebral hemispheres in the acquisition of perceptual skill with novel speech sounds. Two groups of eight subjects rated on three occasions the dissimilarity of pairs of Mandarin Chinese speech sounds varying on voicing and aspiration, presented to the left or right ear with contralateral noise. The experimental group received listening experience with long passages of Mandarin containing the target sounds. Multidimensional scaling analysis of dissimilarity ratings indicated that listening experience leads to increased perceptual differentiation of phonetic categories drawn from a language unfamiliar to the listener. This improvement occurred sooner with presentation of the target sounds to the right hemisphere than to the left if the phonological contrast was along the voicing dimension. Improvement in the perception of stimuli varying on aspiration occurred in right ear presentations only. This finding supports the position that speech perception mechanisms at the feature level may be distributed asymmetrically across the hemispheres.

In the study of language acquisition following early brain damage, results have been divergent. On one hand, some studies claim that language eventually resumes to normal, whereas, on the other hand, studies show lasting deficits throughout development. Discrepancies in the results could arise from different etiologies and tests used. This study attempts to determine the extent to which the development of verb production is affected in later development in children who had simple partial epilepsy (SPE). Measures of diversity and fluency of three verb types, namely main verbs, auxiliary and copula verbs, and nonfinite verbs were used on three children diagnosed as SPE and compared to control groups. Our main results show a limited production of auxiliary verbs. Further analysis of their productions suggest a telegraphic style of speech, as reflected by a superior production of nonfinite verb type compared with normal children. These findings are interpreted as reflecting long-lasting consequences of early brain damage with respect to language development.

The nature of cerebral involvement in the acquisition of language was addressed in this longitudinal study of children with an early diagnosis of epilepsy with simple-partial seizures (SPE) and with epileptogenic foci localized in the left frontal (LF) lobe. Yearly evaluations of six SPE-LF children on tests of linguistic comprehension (pointing, understanding of narrative, and understanding of prepositions) and production (repetition, lexical diversity, and grammatical production) were carried out between the ages of 3 and 8 years and compared to those of large samples of control children on the same tasks and at each age level. Linguistic production of all children were transcribed, coded, and analyzed using the Child Language Data Exchange System (MacWhinney & Snow, 1991). Individual evolution trajectories revealed that SPE-LF children showed a clear dissociation in linguistic performance between comprehension and production. Linguistic comprehension gradually improved to reach normal performance levels by age 7 while linguistic production, even at later stages, remained quite poor. This dissociation in the development of linguistic performance in SPE-LF children suggests a complex interplay between brain maturation dynamics and dysfunction modulating the succession of stages in language development. The observed persistent deficits in specific aspects of linguistic performance argue for an early involvement of the anterior areas of the left cerebral hemisphere in the production of language.

The ability of five language-impaired (LI) children and five matched controls, aged 7–10 years, to discriminate natural pairs of consonant-vowel syllables contrasted on place of articulation and voicing, presented to the right or left ear with white noise in the contralateral ear, was investigated. The general pattern of errors indicated that LI children had more difficulty than controls in discriminating place of articulation contrasts only when they were presented to the left ear, as well as a difficulty in discriminating voice contrasts selective to the right ear. The results are discussed in terms of acoustic integration and suggest that bihemispheric dysfunction is a basis for specific language impairment.

Recent speech perception work with normals and aphasics suggests that the right hemisphere may be more adept than the left at making the voicing discrimination, and the reverse for place of articulation. We examined this right hemisphere voicing effect with natural speech stimuli: stop consonants in pre-, mid-, and postvocalic contexts. Using a neuroelectric event-related potential paradigm, we found numerous effects indicating bilateral components reflecting the voicing and place contrast and unique right hemisphere discrimination of both voicing and place of articulation.