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Biomedical subjects

U Bellugi

Publications and source records attributed to U Bellugi.

At least 55 records · Page 3Linked to original sources
PubMed1992

Dissociation between linguistic and nonlinguistic gestural systems: a case for compositionality.

This paper addresses the issue of the separability of disorders of sign language from disorders of gesture and pantomime. The study of a left-lesioned deaf signer presents one of the most striking examples to date of the cleavage between linguistic signs and manual pantomime. The left-hemisphere lesion produced a marked sign language aphasia disrupting both the production and the comprehension of sign language. However, in sharp contrast to the breakdown of sign language, the ability to communicate in nonlinguistic gesture was remarkably spared. This case has important implications for our understanding of the neural mediation of language and gesture. We argue that the differences observed in the fractionation of linguistic versus nonlinguistic gesture reflect differing degrees of compositionality of systems underlying language and gesture. The compositionality hypothesis receives support for the existence of phonemic paraphasias in sign language production, illustrating structural dissolution which is absent in the production of pantomimic gesture. Understanding the neural encoding of compositional motoric systems may lead to a principled anatomical account of the neural separability of language and gesture. This case provides a powerful indication of the left hemisphere's specialization for language-specific functions.

Aphasia↗
PubMed1992

Fetal alcohol syndrome: a case report of neuropsychological, MRI and EEG assessment of two children.

Neuropsychological, neuroanatomical, and electrophysiological data are presented on two subjects with fetal alcohol syndrome (FAS). Both boys had intelligence quotients in the mentally deficient range and were found to have several other severe, specific deficits. Magnetic resonance imaging showed abnormalities of the corpus callosum, and reductions in the size of the basal ganglia and thalamic structures. No focal abnormalities were noted in the electroencephalogram records, although the electroencephalograms of both boys were moderately abnormal for their age group. A multidisciplinary approach to the study of FAS, hopefully will lead to a more unified concept of the disorder and perhaps indicate specific areas of vulnerability.

Adolescent↗
PubMed1992

Specific neurobehavioral profile of Williams' syndrome is associated with neocerebellar hemispheric preservation.

Previous work demonstrated enlargement of the neocerebellar vermis in Williams' syndrome (WS), despite diminished volumes in the cerebral hemispheres. We present the first in vivo volumetric study of any structure within the cerebellar hemispheres. Using MRI, we identified and reliably measured the neocerebellar tonsils in WS subjects; Down's syndrome (DS) subjects matched for age, IQ, and cerebral volume; and age-matched normal controls. WS tonsils were equal in size to control tonsils and larger than DS tonsils. In proportion to the cerebrum, WS tonsils were larger than controls'. These results coincide with the remarkable neuropsychological preservation of language and affect in WS, despite general cognitive impairment. They contrast with the neocerebellar vermal hypoplasia seen in autism, with its communicative and affective deficits. Additionally, two WS subjects showed Chiari type I malformations, but the average tonsillar position in WS was not found to be different than in controls.

Adolescent↗
PubMed1990

Anomalous brain morphology on magnetic resonance images in Williams syndrome and Down syndrome.

Quantitative studies of brain morphology in a group of subjects with Williams syndrome revealed a distinctive pattern of dysmorphology unlike that observed in another form of mental retardation. Down syndrome. Reduced cerebral size but normal cerebellar size was observed in Williams syndrome, in contrast to reductions in both brain components in Down syndrome. Examination of cerebellar vermal morphology suggested significantly increased area of neocerebellar vermal lobules in Williams syndrome, with low-normal size in the paleocerebellar vermal lobules. Thus, a highly selective effect on brain development appears to accompany Williams syndrome, with some brain subsystems, possibly later-developing ones, relatively spared.

Adolescent↗
PubMed1990

Neuropsychological, neurological, and neuroanatomical profile of Williams syndrome.

The general aim of our research is to understand the brain mechanisms that underlie language and cognition. In this paper, we present a new line of investigation which attempts to forge links between a specific neurodevelopmental disorder, a specific neuropsychological profile, and abnormal brain organization. We report on a dissociation between language and cognitive functions in Williams syndrome adolescents, in contrast to age- and IQ-matched Down syndrome adolescents. The Williams syndrome individuals exhibit an unusual fractionation of higher cortical functioning, with marked cognitive deficits, but selective sparing of syntax. Differences in spatial cognitive abilities in the 2 groups are investigated, showing peaks and valleys of abilities specific to Williams syndrome individuals. These neurobehavioral profiles are explored in light of new evidence regarding neurologic and neuroanatomical differences between the 2 matched groups of adolescents. Results from these combined studies should help clarify the neural systems that mediate language and cognitive functions.

Abnormalities, Multiple↗
PubMed1989

Hand dominance for signing: clues to brain lateralization of language.

Virtually all right-handed individuals are left hemisphere dominant for language. Sign languages of the deaf provide an unusual vehicle for exploring the link between handedness and hemispheric specialization for language since in sign language the hands themselves are the language articulators. Performance of the right and left hand was examined in deaf native users of American Sign Language (ASL) for speeded production of one-handed signs and for shadowing of signed discourse. Opposite patterns of asymmetries in hand performance were found in right- and left-handers. However, left-handers were more flexible than right-handers in signing with their non-preferred hand. Furthermore, unusual patterns of hand use for sign were found in a deaf signer with a left hemisphere lesion, possibly indexing increased mediation of the intact hemisphere. Implications for brain organization of language in a visual-gestural mode are discussed.

Adult↗
PubMed1989

Language, modality and the brain.

Studies of the signed languages of deaf people have shown that fully expressive languages can arise, outside of the mainstream of spoken languages, that exhibit the complexities of linguistic organization found in all spoken languages. Thus, the human capacity for language is not linked to some privileged cognitive-auditory connection. However, the formal properties of languages (spoken or signed) appear to be highly conditioned by the modalities involved in their perception and production. Multi-layering of linguistic elements and the use of space in the service of syntax appear to be modality-determined aspects of signed languages. Analyses of patterns of breakdown of signed languages provide new perspectives on the nature of cerebral organization for language. The studies reviewed in this article show that the left cerebral hemisphere in man is specialized for signed as well as spoken languages, and thus may have an innate predisposition for language, independent of language modality.

Adult↗
PubMed1989

Seeing either the forest or the trees: dissociation in visuospatial processing.

Traditionally, visuospatial processing has resisted fractionation into functional substrates. Recently, however, it has been shown that the brain honors the distinction between global and local processing of hierarchical visual stimuli: unilateral left hemisphere brain-damaged subjects were impaired in their ability to draw the local forms of a hierarchical design, whereas right hemisphere-damaged patients demonstrated the opposite pattern (Delis, Robertson, & Efron, 1986; Delis, Kiefner, & Fridlund, 1988). The present study reports a similar pronounced dissociation in hierarchical visual processing but in quite different populations and in the absence of focal structural brain damage. Mentally retarded subjects with Williams Syndrome are considerably more impaired in global relative to local analysis, whereas subjects with Down Syndrome display the opposite pattern. These results, in concert with other neuropsychological data, are provocative because they suggest that certain cognitive deficits may cluster even in the absence of frank cerebral damage, just as they cluster following insult to one hemisphere. These findings should provide clues to the interrelationship of components of visuospatial processing and other cognitive functions.

Adolescent↗
PubMed1989

Language and cognition in two children with Williams syndrome.

In this study, aspects of language, single-gesture retrieval, combinatorial play, and visual-spatial cognition are reported in two children with Williams syndrome who were in the single-word stage of language acquisition. Williams syndrome children are of particular interest because, when older (10-15 years), they display an unusual profile of abilities that may include superior linguistic performance compared with other aspects of cognition. The two children in the present study are compared to a group of normal children in the single-word stage of language acquisition with a mean age of 14.8 months, a group of single-word stage children who are 6-18 months delayed, and a group of older normal children with a mean age of 23.5 months. Results are compatible with the unusual cognitive profile displayed by older Williams syndrome children. We discuss the possibility that this profile involves mechanisms that extend beyond the boundaries of language proper.

Child, Preschool↗
PubMed1988

Sign language and the brain.

Analysis of the patterns of breakdown of a visuospatial language in deaf signers thus allows new perspectives on the nature and determinants of cerebral specialization for language. First, these data show that hearing and speech are not necessary for the development of hemispheric specialization--sound is not crucial. Second, the data show that in these deaf signers, it is the left hemisphere that is dominant for sign language. The patients with damage to the left hemisphere showed marked sign language deficits but relatively intact capacity for processing nonlanguage visuospatial relations. The patients with damage to the right hemisphere showed much the reverse pattern. Thus, not only is there left hemisphere specialization for language functioning, there is a complementary right hemisphere specialization for visuospatial functioning. The fact that much of the grammatical information is conveyed via spatial manipulation appears not to alter this complementary specialization. Furthermore, the finding that components of sign language (e.g., lexicon and grammar) can be selectively impaired suggests that the functional organization of the brain for sign language may turn out to be modular. Finally, patients with left and right hemisphere damage showed dissociations between two uses of space in the language--one to represent spatial relations and the other to represent syntactic relations. Right hemisphere damage disrupts the former but spares the latter; left hemisphere damage disrupts the use of space for syntactic relations but spares its use for spatial relations. Taken together with studies of the processing of sign language "on line" by neurologically intact deaf signers, these data suggest that the left cerebral hemisphere in humans may have an innate predisposition for language, independent of language modality. Studies of the effects of brain damage on signing make it clear that accounts of hemispheric specialization are oversimplified if stated only in terms of a dichotomy between language and visuospatial functioning. Such studies may also permit us to come closer to the real principles underlying the specializations of the two cerebral hemispheres, since in sign language there is interplay between visuospatial and linguistic relations within the same system.

Aphasia↗
PubMed1984

Visual-spatial processing in deaf brain-damaged signers.

Sign language displays all the complex linguistic structure found in spoken languages, but conveys its syntax in large part by manipulating spatial relations. This study investigated whether deaf signers who rely on a visual-spatial language nonetheless show a principled cortical separation for language and nonlanguage visual-spatial functioning. Four unilaterally brain-damaged deaf signers, fluent in American Sign Language (ASL) before their strokes, served as subjects. Three had damage to the left hemisphere and one had damage to the right hemisphere. They were administered selected tests of nonlanguage visual-spatial processing. The pattern of performance of the four patients across this series of tests suggests that deaf signers show hemispheric specialization for nonlanguage visual-spatial processing that is similar to hearing speaking individuals. The patients with damage to the left hemisphere, in general, appropriately processed visual-spatial relationships, whereas, in contrast, the patient with damage to the right hemisphere showed consistent and severe visual-spatial impairment. The language behavior of these patients was much the opposite, however. Indeed, the most striking separation between linguistic and nonlanguage visual-spatial functions occurred in the left-hemisphere patient who was most severely aphasic for sign language. Her signing was grossly impaired, yet her visual-spatial capacities across the series of tests were surprisingly normal. These data suggest that the two cerebral hemispheres of congenitally deaf signers can develop separate functional specialization for nonlanguage visual-spatial processing and for language processing, even though sign language is conveyed in large part via visual-spatial manipulation.

Adult↗
PubMed1984

Apraxia and aphasia for a visual-gestural language.

Since signed languages utilize visual-gestural channels, their study allows a unique opportunity for insight into the ways language and gesture may be represented in the brain. The separability of apraxia and aphasia for sign language was examined in four deaf signers who had unilateral brain damage, three to the left hemisphere and one to the right hemisphere. These patients were administered various tests for apraxia and a test of pantomime recognition. The patient with damage to the right hemisphere was not apraxic as we would expect. For the patients with damage to the left hemisphere, all of whom were aphasic for sign language, strong dissociations emerged between their capacities for sign language and their nonlinguistic motor skills. The language deficits of these patients seemed related to specific linguistic components of sign language rather than to an underlying motor disorder or an underlying disorder in the capacity to express and comprehend symbols of any kind. This separation between linguistic and nonlinguistic function is all the more striking, because sign language and gesture are transmitted in the same modality.

Adult↗
PubMed1983

Processes controlling human movement: neuromotor constraints on American Sign Language.

The study of sign languages provides a promising vehicle for investigating language production because the movements of the articulators in sign are directly observable. Movement of the hands and arms is an essential element not only in the lexical structure of American Sign Language (ASL), but most strikingly, in the grammatical structure of ASL: It is in patterned changes of the movement of signs that many grammatical attributes are represented. The "phonological" (formational) structure of movement in ASL surely reflects in part constraints on the channel through which it is conveyed. We evaluate the relation between one neuromotor constraint on movement-regulation of final position rather than of movement amplitude-and the phonological structure of movement in ASL. We combine three-dimensional measurements of ASL movements with linguistic analyses of the distinctiveness and predictability of the final position (location) versus the amplitude (length). We show that final position, not movement amplitude, is distinctive in the language and that a phonological rule in ASL predicts variation in movement amplitude-a development which may reflect a neuromuscular constraint on the articulatory mechanism through which the language is conveyed.

Journal Article↗
PubMed1983

Brain organization for language: clues from sign aphasia.

Since sign language conveys many grammatical relations by manipulating spatial relations, its study provides a unique opportunity to investigate cerebral specialization for language. Three deaf signers with damage to the left hemisphere were administered an array of formal sign language tests and a linguistic analysis of their spontaneous signing was performed. All three signers showed aphasia for sign language. Strikingly, in these patients, differential damage within the left hemisphere appeared to lead to selective impairment of the structural layers of sign language (e.g. lexicon versus grammar). These data provide the first demonstration of grammatical breakdown in sign language. Importantly, the language impairments of these patients stood in marked contrast to their relatively intact capacities to process nonlanguage visual-spatial relationships. These results suggest that the two cerebral hemispheres of deaf signers can develop separate specializations for linguistic and for visual-spatial processing, even for a visual-spatial language. They further suggest that the left hemisphere has an innate predisposition for language.

Adult↗
PubMed1981

Perception of American sign language in dynamic point-light displays.

Perception of dynamic events of American Sign Language (ASL) was studied by isolating information about motion in the language from information about form. Four experiments utilized Johansson's technique for presenting biological motion as moving points of light. In the first, deaf signers were highly accurate in matching movements of lexical signs presented in point-light displays to those normally presented. Both discrimination accuracy and the pattern of errors were similar in this matching task to that obtained in a control condition in which the same signs were always represented normally. The second experiment showed that these results held for discrimination of morphological operations presented in point-light displays as well. In the third experiment, signers were able to accurately identify signs of a constant handshape and morphological operations acting on signs presented in point-light displays. Finally, in Experiment 4, we evaluated what aspects of the motion patterns carried most of the information for sign identifiability. We presented signs in point-light displays with certain lights removed and found that the movement of the fingertips, but not of any other pair of points, is necessary for sign identification and that, in general, the more distal the joint, the more information its movement carries.

Adult↗
PubMed1981

Processing of formational, semantic, and iconic information in American sign language.

Three experiments examined short-term encoding processes of deaf signers for different aspects of signs from American Sign Language. Experiment 1 compared short-term memory for lists of formationally similar signs with memory for matched lists of random signs. Just as acoustic similarity of words interferes with short-term memory or word sequences, formational similarity of signs had a marked debilitating effect on the ordered recall of sequences of signs. Experiment 2 evaluated the effects of the semantic similarity of the signs on short-term memory: Semantic similarity had no significant effect on short-term ordered recall of sequences of signs. Experiment 3 studied the role that the iconic (representational) value of signs played in short-term memory. Iconicity also had no reliable effect on short-term recall. These results provide support for the position that deaf signers code signs from American Sign Language at one level in terms of linguistically significant formational parameters. The semantic and iconic information of signs, however, seems to have little effect on short-term memory.

Deafness↗