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D Boatman

Publications and source records attributed to D Boatman.

7 recordsLinked to original sources
PubMed1998

Right hemisphere speech perception revealed by amobarbital injection and electrical interference.

OBJECTIVE: To investigate the right hemispheric speech perception capabilities of an adult right-handed patient with seizures. METHODS: Consecutive, unilateral, intracarotid sodium amobarbital injections and left hemispheric electrical interference mapping were used to determine lateralization and localization of speech perception, measured as syllable discrimination. RESULTS: Syllable discrimination remained intact after left and right intracarotid sodium amobarbital injections. Language otherwise strongly lateralized to the left hemisphere. Despite evidence of bilateral speech perception capabilities, electrical interference testing in the left posterior temporal lobe impaired syllable discrimination. CONCLUSIONS: The results suggest a functionally symmetric, parallel system in the adult brain with preferential use of left hemispheric pathways for speech perception.

Adult↗
PubMed1997

Neuroperceptual differences in consonant and vowel discrimination: as revealed by direct cortical electrical interference.

The effects of direct cortical electrical interference on consonant and vowel discrimination were investigated in five patients with implanted subdural electrode arrays. Without electrical interference, patients performance discriminating consonants and vowels was intact. With electrical interference, consonant discrimination was impaired at one electrode site in each patient on the superior temporal gyrus of the lateral left perisylvian cortex. Conversely, vowel and tone discrimination remained relatively intact when tested with electrical interference at the same site. Analysis of patients' consonant discrimination errors revealed that neither differences in acoustic temporal structure nor syllable position fully account for the consonant-vowel perceptual dissociations elicited. Our data suggest that at the cortical level consonant and vowel perception are intrinsically distinct perceptual phenomena. The selective impairment of consonant, but not vowel, discrimination further suggests that consonant and vowel perception are distinguished by differences in relative dependence on the functional--perhaps integrative--resources of the left lateral superior temporal gyrus.

Adolescent↗
PubMed1997

Why would you remove half a brain? The outcome of 58 children after hemispherectomy-the Johns Hopkins experience: 1968 to 1996.

PURPOSE: To report the outcomes of the 58 hemispherectomies performed at Johns Hopkins between 1968 and January 1996. METHODS: Charts were reviewed of the 58 hemispherectomies performed at Johns Hopkins Medical Institutions by the Pediatric Epilepsy Group during the years 1968 to 1996. Twenty-seven operations were done for Rasmussen's syndrome, 24 operations for cortical dysplasias/hemimegalencephalies, and 7 for Sturge-Weber syndrome or other congenital vascular problems. Seizure control alone did not seem to adequately describe the outcomes of the procedure. Therefore, a score was constructed that included seizure frequency, motor disability, and intellectual handicap. This burden of illness score better described the child's handicap before and after surgery. RESULTS: Perioperative death occurred in 4 out of 58 children. Of the 54 surviving children, 54% (29/54) are seizure-free, 24% (13/54) have nonhandicapping seizures, and 23% (12/54) have residual seizures that interfere to some extent with function. Reduction in seizures was related to the etiology of the unilateral epilepsy. Eighty-nine percent of children with Rasmussen's, 67% of those with dysplasias, and 67% of the vascular group are seizure-free, or have occasional, nonhandicapping seizures. All operations were considered by the parents and the physicians to have been successful in decreasing the burden of illness. In 44 the procedure was very successful, in 7 it was moderately successful, and in 3 it was minimally successful. Success was related to the etiology, and early surgery was preferable. CONCLUSION: Hemispherectomy can be a valuable procedure for relieving the burden of seizures, the burden of medication, and the general dysfunction in children with severe or progressive unilateral cortical disease. Early hemispherectomy, although increasing the hemiparesis in children with Rasmussen's syndrome, relieves the burden of constant seizures and allows the child to return to a more normal life. In children with dysplasias, early surgery can allow the resumption of more normal development.

Adolescent↗
PubMed1995

Auditory speech processing in the left temporal lobe: an electrical interference study.

Auditory syllable discrimination, identification, and comprehension were investigated by direct cortical electrical interference in three patients with indwelling subdural electrode arrays. Without electrical interference, patients performed similarly to matched normal subjects. With electrical interference, selective deficits were observed in the posterior superior temporal (PST) lobes of all three patients. At specific PST sites, only comprehension was impaired, while at proximal sites comprehension and identification were impaired, but discrimination remained intact. At a single PST site, all three auditory speech functions were impaired. These findings suggest that lower-level auditory speech functions can operate independent of higher-level processes, as claimed by traditional hierarchical models. However, analysis of discrimination errors revealed lexical-semantic and phonological effects, suggesting that higher-level functions also influence lower-level processing. These data can be explained by a bidirectional processing model, with differentially weighted connections.

Adolescent↗
PubMed1989

Differentiation of blastocysts derived from in vitro-fertilized rhesus monkey ova.

Six in vitro-fertilized ova were cultured for 10 to 13 days in vitro. All six had formed blastocysts with cavities, five had hatched from the zona pellucida, and one had attached to the substrate. After fixation and preparation for examination by light and electron microscopy, it was determined that all but the youngest blastocysts had developed substantial amounts of syncytial trophoblast, which morphologically resembled the syncytial trophoblast present in the first 2 days of implantation in vivo. One of the smaller blastocysts had developed syncytial trophoblast but had not hatched from the zona. All of the blastocysts showed indications of loss or inadequate development of the inner cell mass constituents, indicating that the culture conditions were suboptimal for these constituents. Apparent C-type virus particles were abundant, budding from the basal surface of the syncytial trophoblast. Because the type of trophoblast formed was that normally associated with epithelial invasion and formation of the trophoblast plate, it is suggested that such blastocysts would be useful for in vitro implantation studies as well as studies of formation of syncytial trophoblast. However, other methods should be developed for study of postimplantation embryo development. It is also noted that the inadequate differentiation of the epiblast and endoderm would not have been apparent without microscopic examination.

Animals↗