Scandinavian audiology. Supplementum最新文献

We review data from our laboratory related to a view of dyslexia as a biological disorder, or deficit, caused by both structural and functional brain abnormalities. The review is focused on central auditory processing in dyslexia, and the possibility that impairments in the auditory or acoustic features of the phonological code may be at the heart of the impairments seen in dyslexia. Three methodological approaches by which to investigate central auditory processing deficits are outlined: dichotic listening (DL) to consonant-vowel syllables; magnetic resonance imaging (MRI), and the use of event-related potentials (ERPs). Consonant-vowel syllable DL is a technique for probing the functional status of phonological processing areas in the superior temporal gyrus, particularly in the left hemisphere. MRI is a corresponding structural, or morphological, measure of anatomical abnormalities in the same brain region, particularly covering the planum temporale area. The ERP technique, and particularly the mismatch negativity (MMN) component, reveals cortical dysfunctions in sensory processing and memory related to basic acoustic events. For all three approaches, the dyslexic children were seen to differ from their control counterparts, including absence of modulation of the right ear advantage (REA), in DL through shifting of attention, smaller left-sided planum temporale asymmetry, and prolonged latency in the MMN ERP complex, particularly in the time-deviant stimulus condition.

For a number of years we have been using open-ended questionnaires in the assessment of hearing disability and handicap, tinnitus complaint behaviour together with shortcomings and benefits of various rehabilitative interventions. More recently we have applied this approach to positive experiences reported by adults who have developed a hearing impairment and to the use of silence or social withdrawal as a communication tactic. In addition, we have asked individuals to rate the magnitude of each of their listed disabilities, handicaps, shortcomings, etc., on a scale to provide a qualitative assessment of each of these elements important to the individual. Such a procedure can be repeated after the intervention to measure changes in such estimates. This approach can thus highlight for the therapist, those elements of the patients' problems which are being well or poorly addressed and hence help them to concentrate their effort on the latter. Results obtained using this technique are presented and discussed.

Auditory perception is defined, here, as the interpretation of sensory evidence, derived from sound, in terms of the objects and events that caused the sound. Like other kinds of perception, it involves the use, not only of sensory evidence, but also of contextual evidence, prior knowledge, memory, attention, and processing skills. Auditory speech perception is special because the events to be perceived are those of language. Similarly, the listener's knowledge base and processing skills must include those related to language in general, and spoken language in particular. The auditory system is complete and functional at birth but myelination continues for several years in the higher auditory pathways. This pattern of anatomical maturation is reflected in electrophysiological responses. Similarly, infants display sophisticated discrimination and recognition ability but psychoacoustic performance does not reach adult levels for several years. Empirical data on the development of auditory processing are sparse, but much work has been done on auditory speech perception. Infants at 6 months demonstrate the beginnings of phonemic classification, and performance improves during childhood in a variety of areas. These include: phonetic contrast perception, phoneme recognition, perception of speech in noise, selective attention, and the use of linguistic context. Experience obviously plays a key role in the development of the knowledge and skills required for auditory perception in general and auditory speech perception in particular. It is tempting to assume that the sensory evidence available to the developing child is determined only by the functional integrity of the peripheral auditory system, independent of auditory experience. There is, however, increasing evidence in animals of the influence of auditory experience on the organization of the auditory pathways. Such organization could increase the sensory evidence made available from patterns of neural excitation produced in the cochlea.

Two-hundred-and-sixty uncooperative children (442 ears) performed auditory brainstem response (ABR) and Electrocochleography (ECochG) in the same diagnostic session under general anaesthesia, and the results obtained with the two different methods were compared. A difference > or = 20 dB between the two methods was found in 134 ears (30.3%). The presence of middle ear effusion and symptoms of a possible central nervous system pathology were considered in order to verify the evidence of a correlation between the difference in ABR-ECochG results and these clinical parameters. The presence of middle ear effusion was not significantly correlated with differences > or = 20 dB (p = 0.1347). On the contrary, the presence of symptoms indicative of a possible central nervous system (CNS) involvement was significantly correlated with differences > or = 20 dB (p = 0.0000). ABR has to be considered the first choice in hearing assessment strategy, either for screening or diagnosis. However, the diagnosis of hearing loss only on the basis of the presence or absence of wave V requires some care in case of suspected central auditory pathway lesions. In these cases, ECochG may be the only reliable diagnostic tool for hearing assessment in uncooperative subjects.

This article describes two research studies on prelingually profoundly deaf children. The first study is on deaf children aged 3.5 to 4.25 years, and the second on deaf children aged 4 to 6 years. Both studies show that speech and speech reading skills in deaf preschool children age 3.5 to 6 years depend strongly on fine motor skill of hand and mouth, successive memory and memory for rhythm. These three interdependent skills are taken as three aspects of eupraxia. Eupraxia is an even stronger predictor of speech and speech reading skill than hearing loss. In deaf children aged 4 to 6, eupraxia is predictive of later reading decoding skills. The second study shows that the visual memory skills of deaf children aged 4 to 6 are predictive of their later passive written vocabulary and reading comprehension skills. Both studies show that on the basis of eupraxia with or without oral language skills statistically significant predictions can be made about later school placement in oral deaf schools, non-oral deaf schools or mainstreaming in regular schools. A diagnostic model is formulated in which eupraxia and visual cognition, as a theory on the normal language development of deaf children, can explain individual differences between deaf children with regard to oral and written communication skills.