Neuroanatomical Profiles of Deafness in the Context of Native Language Experience

Abstract

The study of congenitally deaf adult humans provides an opportunity to examine neuroanatomical plasticity resulting from altered sensory experience. However, attributing the source of the brain's structural variance in the deaf is complicated by the fact that deaf individuals also differ in their language experiences (e.g., sign vs spoken), which likely influence brain anatomy independently. Although the majority of deaf individuals in the United States are born to hearing parents and are exposed to English, not American Sign Language (ASL) as their first language, most studies on deafness have been conducted with deaf native users of ASL (deaf signers). This raises the question of whether observations made in deaf signers can be generalized. Using a factorial design, we compared gray (GMV) and white (WMV) matter volume in deaf and hearing native users of ASL, as well as deaf and hearing native users of English. Main effects analysis of sensory experience revealed less GMV in the deaf groups combined (compared with hearing groups combined) in early visual areas and less WMV in a left early auditory region. The interaction of sensory experience and language experience revealed that deaf native users of English had fewer areas of anatomical differences than did deaf native users of ASL (each compared with their hearing counterparts). For deaf users of ASL specifically, WMV differences resided in language areas such as the left superior temporal and inferior frontal regions. Our results demonstrate that cortical plasticity resulting from deafness depends on language experience and that findings from native signers cannot be generalized.

Differential activity in Heschl's gyrus between deaf and hearing individuals is due to auditory deprivation rather than language modality

“…In addition to the evidence presented above, which suggests that language use (speech and sign) in deaf individuals might result in different crossmodal plasticity in primary auditory areas, the fact that the grey and white matter volume in several brain structures changes according to language experience in deaf individuals, suggests that results from deaf native signers cannot be generalised (Olulade et al, 2014). Characterising which of the components of plastic reorganisation in primary auditory areas of deaf individuals are caused by language modality and which by auditory deprivation is not only important for understanding the basic mechanisms of plastic reorganisation, but also because of its relevance in terms of approaches to language acquisition in deaf children, in particular those who have cochlear implants (CI) or are waiting to receive one.…”

Cochlear Implantation in Adults with Prelingual Deafness - A Case Report

“…Unlike children with prelingual deafness and patients with post lingual deafness, the listening performance of adults with prelingual deafness was usually observed with enormous variability among individual and lower speech perception abilities [1] due to the cortical colonization and reorganization by other sensory modalities [2,3]. The slow progress of listening performance was shown in this 33 years old gentleman.…”

The Neural Basis of Speech Perception through Lipreading and Manual Cues: Evidence from Deaf Native Users of Cued Speech

“…These two interpretations are not easy to disentangle. Olulade et al (2014) showed that cortical plasticity resulting from deafness depends on language experience for auditory and visual areas. If normally hearing participants who are CS-users (parents, teachers, educators of deaf CS-users) also showed activation of posterior STS, the hypothesis that multi-signal integration inside the visual modality occurs in this region of the brain would be reinforced.…”

“…Compared to normally hearing individuals, deaf native users of spoken language have fewer areas of anatomical differences than do deaf native users of ASL (Olulade et al, 2014). The neural processes involved in CS and in AV speech seem, to a certain extent, also similar.…”

“…The modality in which language is conveyed can be very different from one deaf child to another: from auditory-oral (listening, talking, and lipreading and facial expressions, known as speechreading), to visual communication strategies like Cued Speech (CS, supporting perception of spoken language with hand shapes that disambiguate lipreading, see below), and/or Sign Language (SL, sign for each language concept, with a grammar of its own). Recently, Olulade et al (2014) suggested that the nature of language experience (signed vs. oral) has an impact on the development of gray matter volume in the cerebral regions processing language measured in deaf adults, but this point remains to be confirmed.…”