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Biomedical subjects

U Bellugi

Publications and source records attributed to U Bellugi.

At least 19 recordsLinked to original sources
PubMed1997

Neural systems mediating American sign language: effects of sensory experience and age of acquisition.

ERPs were recorded from deaf and hearing native signers and from hearing subjects who acquired ASL late or not at all as they viewed ASL signs that formed sentences. The results were compared across these groups and with those from hearing subjects reading English sentences. The results suggest that there are constraints on the organization of the neural systems that mediate formal languages and that these are independent of the modality through which language is acquired. These include different specializations of anterior and posterior cortical regions in aspects of grammatical and semantic processing and a bias for the left hemisphere to mediate aspects of mnemonic functions in language. Additionally, the results suggest that the nature and timing of sensory and language experience significantly impact the development of the language systems of the brain. Effects of the early acquisition of ASL include an increased role for the right hemisphere and for parietal cortex and this occurs in both hearing and deaf native signers. An increased role of posterior temporal and occipital areas occurs in deaf native signers only and thus may be attributable to auditory deprivation.

Adult↗
PubMed1996

The neurobiology of sign language and its implications for the neural basis of language.

The left cerebral hemisphere is dominant for language, and many aspects of language use are more impaired by damage to the left than the right hemisphere. The basis for this asymmetry, however, is a matter of debate; the left hemisphere may be specialized for processing linguistic information or for some more general function on which language depends, such as the processing of rapidly changing temporal information or execution of complex motor patterns. To investigate these possibilities, we examined the linguistic abilities of 23 sign-language users with unilateral brain lesions. Despite the fact that sign language relies on visuospatial rather than rapid temporal information, the same left-hemispheric dominance emerged. Correlation analyses of the production of sign language versus non-linguistic hand gestures suggest that these processes are largely independent. Our findings support the view that the left-hemisphere dominance for language is not reducible solely to more general sensory or motor processes.

Adult↗
PubMed1996

Competition on the face: affect and language in ASL motherese.

Research on early mother-child interaction has documented the crucial role affect plays in the content and modulation of early interactions. For hearing mothers, voice quality is considered to be the single most informative channel for affective expression. For deaf caregivers who use American Sign Language (ASL), the vocal channel is unavailable, and facial expression is critically important. Not only do facial behaviours signal affective and communicative information, but specific facial behaviours also function as obligatory grammatical markers. This multifunctionality of facial expression presents a dilemma for deaf parents signing to their toddlers as these two systems potentially compete for expression on the face. This study addresses how affective facial expression interacts with the linguistic forms in ASL motherese. To address this issue, we present data from both cross-sectional and longitudinal videotaped interaction from a total of 15 deaf mothers signing with their deaf toddlers (ages 0;9-2;8). Using Ekman & Friesen's Facial Action Coding System (FACS) (1978) we analysed child-directed maternal wh- questions. Because they are frequent in early discourse, and they require furrowed brows which also signal anger and puzzlement, wh- questions represent an ideal context to address the potential conflict of grammatical and affective facial expression in ASL motherese. Our studies indicate a shift from affect to grammar at about the child's second birthday. These findings shed new insight on the nature and possible role of input on the language acquisition process.

Affect↗
PubMed1995

Unique profile of visuo-perceptual skills in a genetic syndrome.

Williams syndrome (WS) and Down syndrome (DS) are genetic disorders with characteristic neuropsychological profiles. Subjects with WS show surface similarities to subjects with right hemisphere damage (RHD) in their relative preservation of linguistic skills, their poor visuo-constructive skills, and their hierarchical processing biases. Ten adolescents and young adults with WS and nine matched subjects with DS were administered a battery of visuospatial perceptual tasks to test whether the profile of performance in WS would resemble that in RHD. It was found instead that the WS subjects showed a distinctive clustering of skills, with particular preservation of facial discrimination, but impairment of other perceptual skills. Subjects with DS showed a more homogeneous profile. The WS profile may map onto the functional dichotomy between ventral and dorsal visual pathways in the cerebral cortex.

Adolescent↗
PubMed1995

A case of 'sign blindness' following left occipital damage in a deaf signer.

We report on a right-handed, deaf, life long signer who suffered a left posterior cerebral artery (PCA) stroke. The patient presented with right homonymous hemianopia, alexia and a severe sign comprehension deficit. Her production of sign language was, however, virtually normal. We suggest that her syndrome can be characterized as a case of 'sign blindness', a disconnection of the intact right hemisphere visual areas from intact left hemisphere language areas. This case provides strong evidence that the neural systems supporting sign language processing are predominantly in the left hemisphere, but also suggests that there are some differences in the neural organization of signed vs spoken language within the left hemisphere.

Female↗
PubMed1994

Cytoarchitectonic anomalies in a genetically based disorder: Williams syndrome.

We report on cytoarchitectonic neocortical findings in a patient with Williams syndrome (WS), a rare genetic disorder resulting in characteristic facies, heart defect, other connective tissue anomalies, and a unique neurobehavioral profile. Cytoarchitectonic anomalies include exaggerated horizontal organization of neurons within layers, most striking in area 17; increased cell packing density throughout brain regions; abnormally clustered and oriented neurons. Overall, posterior forebrain areas were markedly diminished in volume. The results suggest that brain anomalies may relate to the extreme visuospatial deficit in WS, the dysregulation of apoptotic cell death, and the genetic basis of WS, a hemizygous deletion including the elastin locus on chromosome 7. This case provides opportunities for linking brain findings to cognitive deficits and their genetic underpinnings.

Abnormalities, Multiple↗
PubMed1994

Evidence from two genetic syndromes for a dissociation between verbal and visual-spatial short-term memory.

Williams and Down syndromes, two genetic syndromes of abnormal neurodevelopment, are characterized by specific neuropsychological profiles and unique patterns of brain morphology. We find that the superior language ability of subjects with Williams syndrome is accompanied by significantly better performance on a verbal short-term memory task. Conversely, subjects with Down syndrome perform significantly better on a visual-spatial short-term memory task. This double dissociation provides neurogenetic evidence for the distinction between short-term storage for verbal and for visual-spatial stimuli.

Adolescent↗
PubMed1993

Cerebral morphologic distinctions between Williams and Down syndromes.

Neurobehavioral studies of Williams syndrome (WS) and Down syndrome (DS) have revealed distinct profiles of cognitive strengths and weaknesses. In a previous report, we described several gross brain morphologic distinctions on magnetic resonance images between these two disorders. While the observed cerebral hypoplasia was of equal degree in the two groups, cerebellar size was entirely normal in the subjects with WS but dramatically reduced in subjects with DS. In WS, paleocerebellar vermal lobules subtended a smaller area on midsagittal sections, but neocerebellar lobules were actually larger. These results suggested important distinctions between WS and DS in terms of the action and anatomic targets of factors that alter brain development in these syndromes. The present study extends the earlier findings by focusing in detail on the morphologic features of the cerebral hemispheres, particularly cerebral gray matter. The results suggest that some frontal and temporal limbic structures are relatively preserved in WS, while some basal ganglia and diencephalic structures are relatively preserved in DS.

Adolescent↗
PubMed1993

Dissociation of cortical and single unit activity in spoken and signed languages.

Based on stroke and other lesion data, the cortical organization of sign language has been shown to be in the verbal language-dominant hemisphere. However, finer detail of the cortical organization of sign language is not readily available. Intraoperative cortical mapping of spoken and American Sign Language (ASL) was performed in a hearing patient proficient in ASL undergoing an awake operation for intractable epilepsy. We found the dissociation of essential cortical language sites for spoken and signed languages, the relationship of these sites to the interpretation of ASL, and the importance of the anterior temporal lobe in the language-dominant hemisphere for proper ASL handshapes. Single unit recordings in the anterior temporal lobe, at a site later identified to be important in handshape formation, showed sustained activity during naming with superimposed increases in activity during overt speech.

Adult↗
PubMed1993

Visual imagery and visual-spatial language: enhanced imagery abilities in deaf and hearing ASL signers.

The ability to generate visual mental images, to maintain them, and to rotate them was studied in deaf signers of American Sign Language (ASL), hearing signers who have deaf parents, and hearing non-signers. These abilities are hypothesized to be integral to the production and comprehension of ASL. Results indicate that both deaf and hearing ASL signers have an enhanced ability to generate relatively complex images and to detect mirror image reversals. In contrast, there were no group differences in ability to maintain information in images for brief periods or to imagine objects rotating. Signers' enhanced visual imagery abilities may be tied to specific linguistic requirements of ASL (referent visualization, topological classifiers, perspective shift, and reversals during sign perception).

Adult↗
PubMed1992

The linguistic basis of left hemisphere specialization.

In humans the two cerebral hemispheres of the brain are functionally specialized with the left hemisphere predominantly mediating language skills. The basis of this lateralization has been proposed to be differential localization of the linguistic, the motoric, or the symbolic properties of language. To distinguish among these possibilities, lateralization of spoken language, signed language, and nonlinguistic gesture have been compared in deaf and hearing individuals. This analysis, plus additional clinical findings, support a linguistic basis of left hemisphere specialization.

Adult↗
PubMed1992

Callosal morphology concurs with neurobehavioral and neuropathological findings in two neurodevelopmental disorders.

To integrate neuroimaging, neuropathologic, and neuropsychological findings, computer-assisted morphometry was applied to magnetic resonance images of the corpus callosum in adolescents with Down and Williams syndromes and in control subjects. Callosa of subjects with Down syndrome were distinctively rounded in form, consistent with Down syndrome brachycephaly. These callosa also showed decreased widths throughout their rostral fifth, which serves frontal lobe projections. This finding correlates with the hypocellularity and hypofrontality of neocortex in subjects with Down syndrome and with their neuropsychological profile of frontal lobe dysfunction. Callosa of subjects with Williams syndrome generally resembled control specimens, in congruence with their frontal lobe structure and better preserved frontal lobe function. These results represent a convergence of findings across levels of neuroscientific investigation.

Adolescent↗
PubMed1992

Acquisition of signs from American sign language in hearing individuals following left hemisphere damage and aphasia.

Three severely aphasic hearing patients with no prior knowledge of sign language were able to acquire competency in aspects of American Sign Language (ASL) lexicon and finger spelling, in contrast to a near complete inability to speak the English counterparts of these visuo-gestural signs. Two patients with damage in left postero-lateral temporal and inferior parietal cortices mastered production and comprehension of single signs and short meaningful sign sequences, but the one patient with damage to virtually all left temporal cortices was less accurate in single sign processing and was unable to produce sequences of signs at all. These findings suggest that conceptual knowledge is represented independently of the auditory-vocal records for the corresponding lexical entries, and that left anterior temporal cortices outside of traditional "language areas" are part of the neural network which supports the linkage between conceptual knowledge and linguistic signs, especially as they are used in the sequenced activations required for production or comprehension of meaningful sentences.

Adult↗
PubMed1992

Sensitivity to inflectional morphology in aphasia: a real-time processing perspective.

The present study investigates Broca's aphasics' sensitivity to morphological information in an on-line task. German is used as the test language because it is highly inflected. Results from two word monitoring experiments show first that Broca's patients like normal controls are sensitive to the presence of a contextually incorrect inflection. Contrary to normals, they are, however, not sensitive to the absence of an obligatory inflection even when its presence is syntactically highly constrained. Second, they reveal that Broca's aphasics are only sensitive to the presence of an incorrect inflection when it functions as a marker of lexical category (noun vs. verb) and not when it functions as a diacritical marker (second person singular vs. third person singular). The results are taken as evidence for the claim that Broca's aphasics are impaired in the ability to process the full syntactic information encoded in closed class elements in a fast, automatic, and obligatory way.

Adult↗
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↗