Читать книгу The Handbook of Language and Speech Disorders - Группа авторов - Страница 46

A central aim of cochlear implantation is to improve users’ communication abilities relative to those experienced prior to implantation, when they were living with hearing loss and the communication problems that this entails. For the current purpose, communication abilities are taken to refer to linguistic abilities, but in a broad sense, that is, receptive and productive linguistic abilities on several levels, ranging from speech perception and production through morphology and syntax to narratives and pragmatics. On each of these levels, communication problems could be expected to occur given CI users’ fundamental problem of hearing loss. However, as we will see, as a generalization over individuals, it could be stated that implantation alleviates issues on those levels to different degrees, although it must be borne in mind that there exists much individual variation and that many factors influence outcomes. These linguistic domains will be taken up in subsequent parts of this chapter. Moreover, they will be discussed in the context of a basic framework, linking communication according to those several levels.

This model is a general framework of communication abilities that is loosely inspired by Wilson and Cleary’s (1995) theoretical model for linking clinical outcomes to health‐related quality of life (HRQoL); for a discussion of this, see Huber and Havas (2019). Their model is a taxonomy of measures of HRQoL implying that more biological measures, such as disease symptoms, through functional measures, like the ability to perform certain tasks, underlie the encompassing measure of quality of life (QoL). The framework for the current discussion adopts this from a taxonomic approach, basically assuming that the communication problems of CI recipients, on any level, can partially be traced back to their pre‐ and post‐surgery speech perception performance (see Figure 3.2). CI users’ lower‐level auditory acuity problems result in missing out on linguistic information, which in turn causes broader communication and socio‐emotional problems. The framework (see Table 3.1) is a logical assumption for the simple reason that the perception deficits experienced by CI users are the basic characteristics that distinguish CI from non‐CI users.

Table 3.1 A Teleological Framework of Tasks and Levels involved in Speech Perception.

Task	Level
Determine communicative intent	High order—cognitive
Suprasegmental interpretation	Prosody perception—analysis of acoustic surface
Word recognition	Lexical parsing
Segmental recognition	Low order—perceptual

For the current purpose, speech perception is taken to refer to the low and middle levels of the receiver’s involvement in the communication chain, that is, respectively, detection and understanding of speech (recognition of words), both its segmental and suprasegmental layers. Speech perception, in this sense, involves recognition of a sufficient number of phonemes per word or group of words to recognize uttered phrases, that is, the segmental layer, as well as recognition of prosodic patterns. Prosody is defined as the information in the speech signal that is not reducible to the intrinsic and co‐intrinsic segmental information (Rietveld & van Heuven, 2016). Given CI users’ basic hearing deficits, they might prima facie miss out on any of the components of speech perception, including: recognition of segments (vowels and consonants), words, stress and intonation patterns, or prosody, and morphosyntactic understanding. Recent evidence regarding how problematic these areas are for CI users will be discussed in turn. Comprehension of speech (recognition of an utterance’s message) is understood to be a question of the higher post‐lexical level of the speech chain and will be treated separately in a section on morphology and syntax. The same holds for prosody, which has its own communicative functions, that is, apart from those that occur in the segmental layer, as well as, finally, the broader communicative consequences of errors that occur prior to a given level.

The reason for defining this framework in the current chapter is that it simplifies the discussion of what communication problems are for CI users. Furthermore, it provides a unified explanation for those problems, which in turn might direct attention to various rehabilitation approaches. With speech perception problems taken as the basic underlying problem, we start out by reviewing research on those.