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Biomedical subjects

Karen Emmorey

Publications and source records attributed to Karen Emmorey.

13 recordsLinked to original sources
PubMed2006

Laughter among deaf signers.

The placement of laughter in the speech of hearing individuals is not random but "punctuates" speech, occurring during pauses and at phrase boundaries where punctuation would be placed in a transcript of a conversation. For speakers, language is dominant in the competition for the vocal tract since laughter seldom interrupts spoken phrases. For users of American Sign Language, however, laughter and language do not compete in the same way for a single output channel. This study investigated whether laughter occurs simultaneously with signing, or punctuates signing, as it does speech, in 11 signed conversations (with two to five participants) that had at least one instance of audible, vocal laughter. Laughter occurred 2.7 times more often during pauses and at phrase boundaries than simultaneously with a signed utterance. Thus, the production of laughter involves higher order cognitive or linguistic processes rather than the low-level regulation of motor processes competing for a single vocal channel. In an examination of other variables, the social dynamics of deaf and hearing people were similar, with "speakers" (those signing) laughing more than their audiences and females laughing more than males.

Adolescent↗
PubMed2005

Neural organization for recognition of grammatical and emotional facial expressions in deaf ASL signers and hearing nonsigners.

Recognition of emotional facial expressions is universal for all humans, but signed language users must also recognize certain non-affective facial expressions as linguistic markers. fMRI was used to investigate the neural systems underlying recognition of these functionally distinct expressions, comparing deaf ASL signers and hearing nonsigners. Within the superior temporal sulcus (STS), activation for emotional expressions was right lateralized for the hearing group and bilateral for the deaf group. In contrast, activation within STS for linguistic facial expressions was left lateralized only for signers and only when linguistic facial expressions co-occurred with verbs. Within the fusiform gyrus (FG), activation was left lateralized for ASL signers for both expression types, whereas activation was bilateral for both expression types for nonsigners. We propose that left lateralization in FG may be due to continuous analysis of local facial features during on-line sign language processing. The results indicate that function in part drives the lateralization of neural systems that process human facial expressions.

Adult↗
PubMed2005

"Tip of the fingers" experiences by deaf signers: insights into the organization of a sign-based lexicon.

The "tip of the fingers" phenomenon (TOF) for sign language parallels the "tip of the tongue" phenomenon (TOT) for spoken language. During a TOF, signers are sure they know a sign but cannot retrieve it. Although some theories collapse semantics and phonology in sign language and thus predict that TOFs should not occur, TOFs were elicited in the current study. Like TOTs, TOFs often resolve spontaneously, commonly involve targets that are proper names, and frequently include partial access to phonology. Specifically, signers were more likely to retrieve a target sign's handshape, location, and orientation than to retrieve its movement. Signers also frequently recalled the first letter of a finger-spelled word. The existence of TOFs supports two-stage retrieval and a division between semantics and phonology in American Sign Language. The partial phonological information available during TOFs suggests that phonological features are accessed more simultaneously during lexical access for signed language than during lexical access for spoken language.

Adult↗
PubMed2004

The neural correlates of spatial language in English and American Sign Language: a PET study with hearing bilinguals.

Rather than specifying spatial relations with a closed-class set of prepositions, American Sign Language (ASL) encodes spatial relations using space itself via classifier constructions. In these constructions, handshape morphemes specify object type, and the position of the hands in signing space schematically represents the spatial relation between objects. A [15O]water PET study was conducted to investigate the neural regions engaged during the production of English prepositions and ASL locative classifier constructions in hearing subjects with deaf parents (ASL-English bilinguals). Ten subjects viewed line drawings depicting a spatial relation between two objects and were asked to produce either an ASL locative classifier construction or an English preposition that described the spatial relation. The comparison task was to name the figure object (colored red) in either ASL or in English. Describing spatial relations in either ASL or English engaged parietal cortex bilaterally. However, an interaction analysis revealed that right superior parietal cortex was engaged to a greater extent for ASL than for English. We propose that right parietal cortex is involved in the visual-motoric transformation required for ASL. The production of both English prepositions and ASL nouns engaged Broca's area to a greater extent than ASL classifier constructions. We suggest that Broca's area is not engaged because these constructions do not involve retrieval of the name of an object or the name of a spatial relation. Finally, under the same task conditions, only left parietal activation was observed for monolingual English speakers producing spatial prepositions (H. Damasio et al., 2001, NeuroImage, 13). We conclude that the right hemisphere activation observed for ASL-English bilinguals was due to their life-long experience with spatial language in ASL.

Adult↗
PubMed2004

The puzzle of working memory for sign language.

Why is immediate-serial-recall (short-term memory) span consistently shorter for sign language than it is for speech? A new study by Boutla et al. shows that neither the length of signs, nor the formational similarity of signed digits, can account for the difference. Their results suggest instead that the answer lies in differences between the auditory and visual systems. At the same time, however, their results show that sign language and spoken language yield equivalent processing spans, suggesting that reliance on immediate-serial-recall measures in clinical and educational testing is misplaced.

Auditory Perception↗
PubMed2004

Motor-iconicity of sign language does not alter the neural systems underlying tool and action naming.

Positron emission tomography was used to investigate whether the motor-iconic basis of certain forms in American Sign Language (ASL) partially alters the neural systems engaged during lexical retrieval. Most ASL nouns denoting tools and ASL verbs referring to tool-based actions are produced with a handshape representing the human hand holding a tool and with an iconic movement depicting canonical tool use, whereas the visual iconicity of animal signs is more idiosyncratic and inconsistent across signs. We investigated whether the motor-iconic relation between a sign and its referent alters the neural substrate for lexical retrieval in ASL. Ten deaf native ASL signers viewed photographs of tools/utensils or of actions performed with or without an implement and were asked to overtly produce the ASL sign for each object or action. The control task required subjects to judge the orientation of unknown faces. Compared to the control task, naming tools engaged left inferior and middle frontal gyri, bilateral parietal lobe, and posterior inferotemporal cortex. Naming actions performed with or without a tool engaged left inferior frontal gyrus, bilateral parietal lobe, and posterior middle temporal gyrus at the temporo-occipital junction (area MT). When motor-iconic verbs were compared with non-iconic verbs, no differences in neural activation were found. Overall, the results indicate that even when the form of a sign is indistinguishable from a pantomimic gesture, the neural systems underlying its production mirror those engaged when hearing speakers name tools or tool-based actions with speech.

Adult↗
PubMed2004

Conceptual locations and pronominal reference in American Sign Language.

We report the results of an experiment investigating the ramifications of using space to express coreference in American Sign Language (ASL). Nominals in ASL can be associated with locations in signing space, and pronouns are directed toward those locations to convey coreference. A probe recognition technique was used to investigate the case of "locus doubling" in which a single referent is associated with two distinct spatial locations. The experiment explored whether an ASL pronoun activates both its antecedent referent and the location associated with that referent. An introductory discourse associated a referent (e.g, MOTHER) with two distinct locations (eg., STOREleft, KITCHENright), and a continuation sentence followed that either contained a pronoun referring to the referent in one location or contained no anaphora (the control sentence). Twenty-four deaf participants made lexical decisions to probe signs presented during the continuation sentences. The probe signs were either the referent of the pronoun, the referent-location determined by the pronoun, or the most recently mentioned location (not referenced by the pronoun). The results indicated that response times to referent nouns were faster in the pronoun than in the no-pronoun control condition and that response times to the location signs did not differ across conditions. Thus, the spatial nature of coreference in ASL does not alter the processing mechanism underlying the on-line interpretation of pronouns. Pronouns activate only referent nouns, not spatial location nouns associated with the referent.

Adult↗
PubMed2003

A morphometric analysis of auditory brain regions in congenitally deaf adults.

We investigated whether variation in auditory experience in humans during development alters the macroscopic neuroanatomy of primary or auditory association cortices. Volumetric analyses were based on MRI data from 25 congenitally deaf subjects and 25 hearing subjects, all right-handed. The groups were matched for gender and age. Gray and white matter volumes were determined for the temporal lobe, superior temporal gyrus, Heschl's gyrus (HG), and the planum temporale. Deaf and hearing subjects did not differ in the total volume or the gray matter volume of HG, which suggests that auditory deafferentation does not lead to cell loss within primary auditory cortex in humans. However, deaf subjects had significantly larger gray matter-white matter ratios than hearing subjects in HG, with deaf subjects exhibiting significantly less white matter in both left and right HG. Deaf subjects also had higher gray matter-white matter ratios in the rest of the superior temporal gyrus, but this pattern was not observed for the temporal lobe as a whole. These findings suggest that auditory deprivation from birth results in less myelination and/or fewer fibers projecting to and from auditory cortices. Finally, the volumes of planum temporale and HG were significantly larger in the left hemisphere for both groups, suggesting that leftward asymmetries within "auditory" cortices do not arise from experience with auditory processing.

Adult↗
PubMed2003

Neural systems underlying lexical retrieval for sign language.

Positron emission tomography was used to investigate whether signed languages exhibit the same neural organization for lexical retrieval within classical and non-classical language areas as has been described for spoken English. Ten deaf native American sign language (ASL) signers were shown pictures of unique entities (famous persons) and non-unique entities (animals) and were asked to name each stimulus with an overt signed response. Proper name signed responses to famous people were fingerspelled, and common noun responses to animals were both fingerspelled and signed with native ASL signs. In general, retrieving ASL signs activated neural sites similar to those activated by hearing subjects retrieving English words. Naming famous persons activated the left temporal pole (TP), whereas naming animals (whether fingerspelled or signed) activated left inferotemporal (IT) cortex. The retrieval of fingerspelled and native signs generally engaged the same cortical regions, but fingerspelled signs in addition activated a premotor region, perhaps due to the increased motor planning and sequencing demanded by fingerspelling. Native signs activated portions of the left supramarginal gyrus (SMG), an area previously implicated in the retrieval of phonological features of ASL signs. Overall, the findings indicate that similar neuroanatomical areas are involved in lexical retrieval for both signs and words.

Adult↗
PubMed2003

The effect of irrelevant visual input on working memory for sign language.

We report results showing that working memory for American Sign Language (ASL) is sensitive to irrelevant signed input (and other structured visual input) in a manner similar to the effects of irrelevant auditory input on working memory for speech. Deaf signers were disrupted on serial recall of lists of ASL signs when either pseudosigns or moving shapes were presented during a retention interval. Hearing subjects asked to recall lists of printed English words did not show disruption under the same interference conditions. The results favor models that hypothesize modality-specific representations of language within working memory, as opposed to amodal representations. The results further indicate that working memory for sign language involves visual or quasi-visual representations, suggesting parallels to visuospatial working memory.

Journal Article↗
PubMed2002

Neural systems underlying spatial language in American Sign Language.

A [(15)O]water PET experiment was conducted to investigate the neural regions engaged in processing constructions unique to signed languages: classifier predicates in which the position of the hands in signing space schematically represents spatial relations among objects. Ten deaf native signers viewed line drawings depicting a spatial relation between two objects (e.g., a cup on a table) and were asked either to produce a classifier construction or an American Sign Language (ASL) preposition that described the spatial relation or to name the figure object (colored red). Compared to naming objects, describing spatial relationships with classifier constructions engaged the supramarginal gyrus (SMG) within both hemispheres. Compared to naming objects, naming spatial relations with ASL prepositions engaged only the right SMG. Previous research indicates that retrieval of English prepositions engages both right and left SMG, but more inferiorly than for ASL classifier constructions. Compared to ASL prepositions, naming spatial relations with classifier constructions engaged left inferior temporal (IT) cortex, a region activated when naming concrete objects in either ASL or English. Left IT may be engaged because the handshapes in classifier constructions encode information about object type (e.g., flat surface). Overall, the results suggest more right hemisphere involvement when expressing spatial relations in ASL, perhaps because signing space is used to encode the spatial relationship between objects.

Adult↗