Neural systems underlying lexical retrieval for sign language

Abstract

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.

Monitoring Different Phonological Parameters of Sign Language Engages the Same Cortical Language Network but Distinctive Perceptual Ones

“…We also observed that nonsigns caused a stronger activation, only in deaf signers, in the SMG. This effect suggests a modulation of phoneme monitoring by phonological structure of the signal and corroborates the role of this area in phonological processing of signed (MacSweeney, Emmorey et al, 2002Emmorey et al, , 2007Emmorey, Grabowski, et al, 2003;MacSweeney, Woll, Campbell, Calvert, et al, 2002;Corina et al, 1999) and spoken language (Sliwinska, Khadilkar, Campbell-Ratcliffe, Quevenco, & Devlin, 2012;Hartwigsen et al, 2010). It also demonstrates that an increase in processing demands when stimuli are less coherent is seen not only at a perceptual level but also at a linguistic one.…”

Neural systems for sign language production: Mechanisms supporting lexical selection, phonological encoding, and articulation

“…More recently, a small but growing number of neuroimaging studies have begun to provide a more detailed picture of the neural architecture mediating sign language processing in non-brain-damaged adults. These studies have consistently revealed that classic lefthemisphere perisylvian language areas, similar to those implicated in spoken language, mediate processing of sign language in profoundly deaf, life-long signers Emmorey et al, 2002Emmorey et al, , 2003MacSweeney et al, 2002;McGuire et al, 1997;Neville et al, 1998;Petitto et al, 2000]. In addition, some studies of sign language comprehension have shown greater right hemisphere contributions during sign language processing that are not evident during processing of written language Neville et al, 1998;Newman et al, 2002].…”

“…In contrast, positron emission tomography studies of sign language production have typically observed largely left-lateralized brain activation. For example, studies of single sign production in British Sign Language [McGuire et al, 1997], Langue des Signes Quebecoise [Petitto, et al, 2000], and ASL [Corina et al, 2003;Emmorey et al, 2003] reported that deaf subjects activated left inferior frontal regions and superior temporal regions similar to those that mediate speech in hearing subjects. 1 As functional imaging studies continue to explore the neural correlates of sign processing, the questions being addressed have begun to broaden.…”

“…Initial studies, using single contrast designs in the context of between group manipulation (e.g., deaf vs. hearing) aimed at illuminating how sign language activation differs from spoken or written language processing [MacSweeny et al, 2002;Neville et al, 1998]. Others studies have explicated changes in a small set of regions, selected on the basis of spoken language processing [Emmorey et al, 2002[Emmorey et al, , 2003McGuire et al, 1997;Petitto et al, 2000]. More recently, studies have begun to explore properties that are unique to sign languages [Corina et al, 2003;Emmorey et al, 2003;MacSweeney et al, 2002].…”

“…Petitto et al [2000] constructed contrasts between various tasks, including passive viewing of fixation cross, passive watching of non-signs, passive viewing of real signs; repetition of signs; and verb generation. Emmorey et al [2003] examined naming faces and animals including both sign and finger spelling, compared to a baseline of a signed yes-no judgment of an inverted face. Emmorey et al [2002] examined production of a special class of ASL sign classifier that may not have a direct analogue in spoken English.…”