Biomedical subjects
E S Klima
Publications and source records attributed to E S Klima.
Discourse deficits following right hemisphere damage in deaf signers.
Previous findings have demonstrated that hemispheric organization in deaf users of American Sign Language (ASL) parallels that of the hearing population, with the left hemisphere showing dominance for grammatical linguistic functions and the right hemisphere showing specialization for non-linguistic spatial functions. The present study addresses two further questions: first, do extra-grammatical discourse functions in deaf signers show the same right-hemisphere dominance observed for discourse functions in hearing subjects; and second, do discourse functions in ASL that employ spatial relations depend upon more general intact spatial cognitive abilities? We report findings from two right-hemisphere damaged deaf signers, both of whom show disruption of discourse functions in absence of any disruption of grammatical functions. The exact nature of the disruption differs for the two subjects, however. Subject AR shows difficulty in maintaining topical coherence, while SJ shows difficulty in employing spatial discourse devices. Further, the two subjects are equally impaired on non-linguistic spatial tasks, indicating that spared spatial discourse functions can occur even when more general spatial cognition is disrupted. We conclude that, as in the hearing population, discourse functions involve the right hemisphere; that distinct discourse functions can be dissociated from one another in ASL; and that brain organization for linguistic spatial devices is driven by its functional role in language processing, rather than by its surface, spatial characteristics.
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.
Biological foundations of language: clues from sign language.
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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.
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.
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.
Representation of inflected signs from American sign language in short-term memory.
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Nonauditory suffix effects in congenitally deaf signers of American Sign Language.
A series of unordered recall tasks was administered to groups of congenitally deaf subjects for whom American Sign Language (ASL) is the principal means of communication. A suffix effect was observed when an ASL sign was suffixed to a list of ASL signs (Experiment 1), and when a line drawing of an ASL sign was suffixed to a list of line drawings of ASL signs (Experiment 3). The suffix effect was a diminished magnitude when a printed English word was suffixed to a list of printed words (Experiment 2). The findings of Experiment 1 and 3 argue conclusively against the suffix effect resulting solely from sensory store differences. Additionally, the results of Experiment 3 argue conclusively against explanation of the effect as arising solely from differences in the processing of "static" versus "changing-state" input.
Language: perspectives from another modality.
Human languages have been forged in auditory-vocal channels throughout evolution. This paper examines the formal properties of a communication system that has developed in the absence of speech: the sign language of the deaf. The objective is to investigate to what extent the overall form and organization of language is determined by the articulatory and perceptual modality in which it has developed (its transmission system) and to what extent its form and organization represent more fundamental aspects of the human mind (intellect). Experimental and linguistic evidence is brought to bear on the analysis of the sign: studies of coding and processing of signs in memory; of slips of the hand; of historical change in signs over time; the heightened use of language in poetry and wit. American Sign Language differs dramatically from English and other spoken languages in the mechanisms by which its lexical units are modified. For the form of its morphological processes, the mode in which the language develops appears to make a crucial difference. Finally, the issue of cerebral specialization with respect to a visual-manual language is addressed.
Two faces of sign: iconic and abstract.
In this paper, we show that the total range of the communication system of the deaf is considerably enriched but at the same time rendered more difficult to analyze, because pantomime and other spontaneous nonsign representations occur in the same mode as regular ASL signs in deaf discourse. We note that the rarification of what was originally nonsign depiction is clearly an important source of regular ASL signs. We show that criteria can be established that would distinguish the clear cases of pantomime from the regular ASL signs. Nonetheless, there remain a sizable number of regular ASL signs which, although they are neither pantomimic nor otherwise freely mimetic, still appear to retain an iconic cast. We show that very few ASL signs are actually transparent; that is, a nonsigner cannot guess the meaning of a sign in the absence of further information. On the other hand, many signs are iconic in the sence that nonsigners, when given the sign and its meaning, show considerable agreement in how the two are related. More important in terms of language and its users is the significance of iconicity for deaf signers themselves. This paper shows that while in special circumstances the deaf do play on iconic elements of certain signs for special effects, iconicity plays no observable role in the coding of signs in short-term memory. The abstract formational parameters definitely dominate. We further note that it is the abstract system and not purely iconic aspects that have determined observed historical changes in the form of ASL signs. We interpret this as indicating the deeper structural significance of the abstract formational level. Finally, we show that very widespread and productive grammatical processes, especially suited for a visual-gestural language, override the iconic aspects of signs also at the synchronic structural level.
Perception and production in a visually based language.
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The basis of the neural organization for language: evidence from sign language aphasia.
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