Brain systems mediating semantic and syntactic processing in deaf native signers: Biological invariance and modality specificity

Abstract

Studies of written and spoken language suggest that nonidentical brain networks support semantic and syntactic processing. Eventrelated brain potential (ERP) studies of spoken and written languages show that semantic anomalies elicit a posterior bilateral N400, whereas syntactic anomalies elicit a left anterior negativity, followed by a broadly distributed late positivity. The present study assessed whether these ERP indicators index the activity of language systems specific for the processing of aural-oral language or if they index neural systems underlying any natural language, including sign language. The syntax of a signed language is mediated through space. Thus the question arises of whether the comprehension of a signed language requires neural systems specific for this kind of code. Deaf native users of American Sign Language (ASL) were presented signed sentences that were either correct or that contained either a semantic or a syntactic error (1 of 2 types of verb agreement errors). ASL sentences were presented at the natural rate of signing, while the electroencephalogram was recorded. As predicted on the basis of earlier studies, an N400 was elicited by semantic violations. In addition, signed syntactic violations elicited an early frontal negativity and a later posterior positivity. Crucially, the distribution of the anterior negativity varied as a function of the type of syntactic violation, suggesting a unique involvement of spatial processing in signed syntax. Together, these findings suggest that biological constraints and experience shape the development of neural systems important for language.electrophysiology ͉ sign language ͉ syntax S igned languages, such as American Sign Language (ASL), are fully developed, natural languages containing all of the linguistic components of spoken languages, but they are conveyed and perceived in a completely different form than those used for aural-oral languages. (Aural-oral is used here to refer to both written and spoken language forms.) Thus, investigations of signed language processing provide a unique opportunity for determining the neural substrates of natural human language irrespective of language form. The present study used eventrelated brain potentials (ERPs) to examine semantic and syntactic processing of ASL sentences in deaf native signers of ASL and compared these findings to those from previous studies of aural-oral language.Lesion and neuroimaging studies suggest that remarkably similar neural systems underlie signed and spoken language comprehension and production. The studies illustrate the importance of a left frontotemporal network for language processing irrespective of the modality through which language is perceived. In particular, neuroimaging studies of sentence processing using written (e.g., refs. 1 and 2), spoken (e.g., refs. 3-5), and audiovisual (6, 7) stimuli have shown reliable left hemisphere-dominant activation in regions such as the inferior frontal gyrus and the posterior superior temporal cortex in hearing users of spok...

ERP correlates of German Sign Language processing in deaf native signers

“…The anterior negativity was followed by a broadly distributed positivity with a central maximum. Both effects were highly similar to what has been observed previously, following both a large number of different syntactic anomalies in aural-oral languages [21,25] and verb agreement violations in ASL [40]. However, our effects emerged later than in these studies [40].…”

“…Thus, another account for the different distributions of the N400 effect in the present and in the study of Capek et al [40] may be the use of critical words from different word classes. Indeed, in an accompanying experiment with written German sentences, we found a similar posterior topography of the N400 in the Deaf native signers as observed in hearing L1 and hearing L2 users of German [51].…”

“…A recent ERP study by Capek et al has, in addition, investigated the processing of continuously presented ASL sentences [40]. Deaf native users of ASL watched signed sentences that were correct or comprised either a semantic violation (implausible sign) or a morphosyntactic verb agreement error.…”

Deafferentation of the Affected Arm

“…Other motor aspects, eg, muscle synergies, are less likely to be affected. 52 Finally, there are some hints that intermodal plasticity 53 could potentially contribute to the improvement of GOT performance. Nevertheless, it seems unlikely that TFD would affect any of these elements of the task, especially the visual, in a way that would be able to account for our results.…”

Seeing facial motion affects auditory processing in noise

“…Implications for auditory-visual speech perception development Sensory and language experience early in life impacts neurological development and processing (Bavelier et al, 2001;Capek et al, 2009;Neville et al, 1998;Ponton & Eggermont, 2001;Sharma, Dorman, & Spahr, 2002): If auditory stimulation is not received within a sensitive period, sensory processing follows a different developmental path, as measured by the P1 auditory evoked potential (see Sharma, Nash, & Dorman, 2009, for a review). Children with hearing loss have different experience not only with auditory sensory stimulation, but also with associating auditory and visual sensory stimulation.…”