Investigating grammatical word class distinctions in bilingual aphasic individuals

Abstract

This chapter will review two major areas in the aphasiology literature, (i) grammatical word class processing by aphasic individuals and (ii) bilingual aphasia, each of which is essential to an understanding of the topic. The first relates to grammatical word class processing, specifically that for verbs and nouns. This area is extremely important because word-finding difficulties for verbs and nouns are so common in aphasia. Also, the processing differences between verbs and nouns that occur at various levels of linguistic analysis: semantic, syntactic, morphological, and phonological will be highlighted. In addition, an overview of the major research studies that have specifically investigated verb-noun dissociations and the patterns of verb and noun impairments in aphasic syndromes is provided. Evidence from neuroimaging studies is also reviewed. The findings reported will be considered in relation to explanatory models locating the breakdown at either linguistic or neuroanatomical levels. Furthermore, in this chapter, I will focus on grammatical word class breakdown in the context of bilingual aphasia. This section will highlight what little is known about how verbs and nouns are processed in bilingual patients due to the reliance on monolingual subjects in these studies. I will present up-to-date research available on investigating grammatical word class distinctions and, indeed, in different languages, in people with bilingual aphasia. This focus is also significant for a theoretical understanding of verb and noun retrieval in bilingual aphasia and models of language processing. The development of theoretical understandings of language processing are, so far, based mainly on monolingual subjects and these models reflect their word retrieval in one language only. However, there is good reason to assume that when people speak two languages with different underlying forms, verbs and nouns may be affected differently. The aim of this chapter is an important one given that aphasia in bilinguals and multilinguals is a rather neglected area of research. As a result, there are many significant gaps in the literature regarding issues of assessment and intervention in bilingual aphasia. This is considered a significant omission given that the number of bilingual speakers was acknowledged as outnumbering those of monolingual speakers since the late 1960s. Specifically, this knowledge base does not reflect the changing demographic picture, in most of the developed world. It is increasingly common for people to speak more than one language due to migration and world globalization. However, despite the recommendations made by peak bodies representing speech pathologists (a term synonymous with speech-language pathologist and speech therapist), which demand equitable services for people from culturally and linguistically diverse backgrounds, the number of bilingual speech pathologists remains low. This means that not only are there insufficient services available for bilingual populations, but also that clinical and theoretical developments in speech pathology have not kept pace with demographic changes. In particular, clinical understanding of language breakdown because of aphasia in two (or more) languages remains poorly understood and clinicians have insufficient knowledge on which to base their interventions.