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PubMed1994

Cochlear implants for congenitally deaf adolescents: is open-set speech perception a realistic expectation?

The prognosis for benefit from use of cochlear implants in congenitally deaf adolescents, who have a long duration of profound deafness prior to implantation, has typically been low. Speech perception results for two congenitally deaf patients implanted as adolescents at the University of Melbourne/Royal Victorian Eye and Ear Hospital Clinic show that, after 12 months of experience, both patients had significant open-set speech discrimination scores without lipreading. These results suggest that although benefits may in general be low for congenitally deaf adolescents, individuals may attain significant benefits to speech perception after a short period of experience. Prospective patients from this group should therefore be considered on an individual basis with regard to prognosis for benefit from cochlear implantation.

Adolescent↗
PubMedDate not supplied

Development of language and speech perception in congenitally, profoundly deaf children as a function of age at cochlear implantation.

Like any other surgery requiring anesthesia, cochlear implantation in the first few years of life carries potential risks, which makes it important to assess the potential benefits. This study introduces a new method to assess the effect of age at implantation on cochlear implant outcomes: developmental trajectory analysis (DTA). DTA compares curves representing change in an outcome measure over time (i.e. developmental trajectories) for two groups of children that differ along a potentially important independent variable (e.g. age at intervention). This method was used to compare language development and speech perception outcomes in children who received cochlear implants in the second, third or fourth year of life. Within this range of age at implantation, it was found that implantation before the age of 2 resulted in speech perception and language advantages that were significant both from a statistical and a practical point of view. Additionally, the present results are consistent with the existence of a 'sensitive period' for language development, a gradual decline in language acquisition skills as a function of age.

Age Factors↗
PubMed1991

Relative performance of single-channel and multichannel tactile aids for speech perception.

Although the results from a number of studies of the performance of multichannel tactile aids for speech perception have suggested that such devices might provide more benefit to hearing-impaired persons than single-channel tactile aids (3,4), recent studies involving direct comparisons of multichannel and single-channel vibrotactile aids (5,6) indicated otherwise. In fact, for some types of speech information, such as rhythm and stress perception, single-channel aids were shown to be superior. The present study attempted to address this apparent discrepancy by comparing the performance of two single-channel devices with two multichannel devices in a variety of speech perception tasks including both single-item and connected speech stimuli. Results indicated that the two classes of tactile device performed similarly in rhythm and stress perception, but that the multichannel aids in many cases showed better performance for tasks in which the identification of fine-structure phoneme information was required (both single-item and connected speech). Results are discussed in terms of the possibility that the performance of a specific multichannel tactile aid cannot be considered indicative of all devices of the same class.

Communication Devices for People with Disabilities↗
PubMed2003

The role of facial colour and luminance in visual and audiovisual speech perception.

We conducted four experiments to investigate the role of colour and luminance information in visual and audiovisual speech perception. In experiments 1a (stimuli presented in quiet conditions) and 1b (stimuli presented in auditory noise), face display types comprised naturalistic colour (NC), grey-scale (GS), and luminance inverted (LI) faces. In experiments 2a (quiet) and 2b (noise), face display types comprised NC, colour inverted (CI), LI, and colour and luminance inverted (CLI) faces. Six syllables and twenty-two words were used to produce auditory and visual speech stimuli. Auditory and visual signals were combined to produce congruent and incongruent audiovisual speech stimuli. Experiments 1a and 1b showed that perception of visual speech, and its influence on identifying the auditory components of congruent and incongruent audiovisual speech, was less for LI than for either NC or GS faces, which produced identical results. Experiments 2a and 2b showed that perception of visual speech, and influences on perception of incongruent auditory speech, was less for LI and CLI faces than for NC and CI faces (which produced identical patterns of performance). Our findings for NC and CI faces suggest that colour is not critical for perception of visual and audiovisual speech. The effect of luminance inversion on performance accuracy was relatively small (5%), which suggests that the luminance information preserved in LI faces is important for the processing of visual and audiovisual speech.

Acoustic Stimulation↗
PubMed1975

Auditory and phonetic levels of processing in speech perception: neurophysiological and information-processing analyses.

Two new experimental operations were used to distinguish between auditory and phonetic levels of processing in speech perception: the first based on reaction time data in speeded classification tasks with synthetic speech stimuli, and the second based on average evoked potentials recorded concurrently in the same tasks. Each of four experiments compared the processing of two different dimensions of the same synthetic consonant-vowel syllables. When a phonetic dimensions was compared to an auditory dimension, different patterns of results were obtained in both the reaction time and evoked potential data. No such differences were obtained for isolated acoustic components of the phonetic dimension or for two purely auditory dimensions. Together with other recent evidence, the present results constitute additional converging operations on the distinction between auditory and phonetic processes in speech perception and on the idea that phonetic processing involves mechanisms that are lateralized in one cerebral hemisphere.

Acoustic Stimulation↗
PubMed2005

An artificial environment is often a noisy environment: auditory scene analysis and speech perception in noise.

Our auditory system has to organize and to pick up a target sound with many components, sometimes rejecting irrelevant sound components, but sometimes forming multiple streams including the target stream. This situation is well described with the concept of auditory scene analysis. Research on speech perception in noise is closely related to auditory scene analysis. This paper briefly reviews the concept of auditory scene analysis and previous and ongoing research on speech perception in noise, and discusses the future direction of research. Further experimental investigations are needed to understand our perceptual mechanisms better.

Auditory Pathways↗
PubMed1997

The relation between age at the time of cochlear implantation and long-term speech perception abilities in congenitally deaf subjects.

The issue of whether an upper age limit should be set for cochlear implantation in congenitally deaf subjects has often been debated. To gain more insight, the speech perception abilities were analyzed of 12 congenitally deaf subjects whose age at the time of cochlear implantation ranged from 4 to 33 years. Subjects implanted during adulthood only showed progress during the first few months after the speech processor had been fitted and their long-term results were poor compared to those of children implanted early in life. This latter group showed steady improvement over the whole evaluation period. The present results support the notion that the earlier in life implantation is performed, the better the development of speech perception. Based on the progress-over-time profiles and data on actual daily use of the cochlear implant, it can be suggested that implantation of congenitally deaf subjects during or after puberty offers only limited benefit.

Adolescent↗
PubMed2004

In search of the auditory, phonetic, and/or phonological problems in dyslexia: context effects in speech perception.

There is a growing consensus that developmental dyslexia is associated with a phonological-core deficit. One symptom of this phonological deficit is a subtle speech-perception deficit. The auditory basis of this deficit is still hotly debated. If people with dyslexia, however, do not have an auditory deficit and perceive the underlying acoustic dimensions of speech as well as people who read normally, then why do they exhibit a categorical-perception deficit? A potential answer to this conundrum lies in the possibility that people with dyslexia do not adequately handle the context-dependent variation that speech signals typically contain. A mathematical model simulating such a sensitivity deficit mimics the speech-perception deficits attributed to dyslexia. To assess the nature of the dyslexic problem, the authors examined whether children with dyslexia handle context dependencies in speech differently than do normal-reading individuals. Contrary to the initial hypothesis, children with dyslexia did not show less context sensitivity in speech perception than did normal-reading individuals at auditory, phonetic, and phonological levels of processing, nor did they reveal any categorization deficit. Instead, intrinsic properties of online phonological processes, not phonological representations per se, may be impaired in dyslexia.

Acoustic Stimulation↗
PubMed1996

Speech perception of temporally reversed syllables by normally hearing adults.

BACKGROUND: The general purpose of this study was to determine the effects of phonological knowledge on performance on a simple task of speech discrimination. If a test can be devised that is independent of the subject's phonological knowledge then it should be possible to measure auditory speech perception capacity in young deaf children before they have developed spoken language skills. In the present study, temporal reversal was used to limit normal subjects' use of phonological knowledge without removing acoustic information. METHODS: An auditory, 3-interval, forced-choice (oddity) test of phonetic contrast perception was administered to 5 normally hearing adult speakers of English. Perception of place of articulation was measured in stops and fricatives--both voiced and unvoiced. The test was presented both with natural syllables and with the same syllables reversed in time. In addition, the test was administered with a fixed context and a mixed context (i.e., context changing from trial to trial). The subject's task was always to identify the odd-man-out in each presentation of 3 syllables. RESULTS: Overall, error rate was significantly higher for temporally-reversed than for natural syllables (6.7% versus 1.7%). The effect was, however, present only in stops (11.7% versus 1.7%) and not in fricatives (0.8% versus 0.8%). Changing from a fixed to a mixed context did not influence the effect of reversal. There were, however, significant differences among subjects in the temporally-reversed condition. CONCLUSIONS: The main effect of reversal supports the hypothesis that performance falls, even on a simple task, when phonetic processing is impeded. The fact that the effect is present only for stops adds further support, because temporal reversal does not affect the essential acoustic properties of fricatives. The presence of inter-subject differences suggests that the ability to switch to an acoustic strategy when phonetic processing is impeded may be affected by aptitude and experience. The fact that error rate was low, even for reversed stops, suggests that a test of this type could be used for assessing speech perception capacity in deaf children with impaired phonology. The procedure is not, however, completely independent of the effects of phonetic processing.

Adult↗
PubMed2006

Neural responses to non-native phonemes varying in producibility: evidence for the sensorimotor nature of speech perception.

Neural responses to unfamiliar non-native phonemes varying in the extent to which they can be articulated were studied with functional magnetic resonance imaging (fMRI). Both superior temporal (auditory) and precentral (motor) areas were activated by passive speech perception, and both distinguished non-native from native phonemes, with greater signal change in response to non-native phonemes. Furthermore, speech-responsive motor regions and superior temporal sites were functionally connected. However, only in auditory areas did activity covary with the producibility of non-native phonemes. These data suggest that auditory areas are crucial for the transformation from acoustic signal to phonetic code, but the motor system also plays an active role, which may involve the internal generation of candidate phonemic categorizations. These 'motor' categorizations would then be compared to the acoustic input in auditory areas. The data suggest that speech perception is neither purely sensory nor motor, but rather a sensorimotor process.

Adolescent↗
PubMed1995

The transmission of phoneme-level information by multichannel tactile speech perception aids.

Current research on the effectiveness of tactile aids for speech perception by hearing-impaired persons suggests that substantial training, lasting over months or years, is necessary for users to achieve maximal benefits from a tactile device. A number of studies have demonstrated the usefulness of training programs that include an analytic component, such as phoneme training, together with more synthetic tasks such as sentence identification and speech tracking. However, particularly in programs for children, it is desirable to structure training experiences so that easy distinctions are trained first, and more difficult distinctions are approached only later in training. In the present study, a systematic evaluation of phoneme-level information provided by the Tactaid VII, a multichannel tactile aid, was performed. Adult subjects were tested in minimal pairs and closed set phoneme discrimination and identification tasks under tactile aid alone, speechreading alone, and speechreading plus tactile aid conditions, to provide an inventory of stimulus identifiability and permit ranking of discriminations as easy or more difficult. Because these rankings might differ as a function of coarticulation effects, three different vowel contexts were tested for consonant stimuli. Results indicated that there were indeed considerable differences across vowel contexts, and that the /ae/ vowel context yielded the most identifiable stimuli. These data could be used by teachers and therapists to construct viable stimulus sets for training programs for tactile aid users.

Adult↗
PubMed2006

Spectral and temporal cues in cochlear implant speech perception.

OBJECTIVE: Taking advantage of the flexibility in the number of stimulating electrodes and the stimulation rate in a modern cochlear implant, the present study evaluated relative contributions of spectral and temporal cues to cochlear implant speech perception. DESIGN: Four experiments were conducted by using a Research Interface Box in five MED-EL COMBI 40+ cochlear implant users. Experiment 1 varied the number of electrodes from four to twelve or the maximal number of available active electrodes while keeping a constant stimulation rate at 1000 Hz per electrode. Experiment 2 varied the stimulation rate from 1000 to 4000 Hz per electrode on four pairs of fixed electrodes. Experiment 3 covaried the number of stimulating electrodes and the stimulation rate to study the trade-off between spectral and temporal cues. Experiment 4 studied the effects of envelope extraction on speech perception and listening preference, including half-wave rectification, full-wave rectification, and the Hilbert transform. Vowels, consonants, and HINT sentences in quiet, as well as with a competing female voice served as test materials. RESULTS: Experiment 1 found significant improvement in all speech tests with a higher number of stimulating electrodes. Experiment 2 found a significant advantage of the high stimulation rate only on consonant recognition and sentence recognition in noise. Experiment 3 found an almost linear trade-off between the number of stimulation electrodes and the stimulation rate for consonant and sentence recognition in quiet, but not for vowel and sentence recognition in noise. Experiment 4 found significantly better performance with the Hilbert transform and the full-wave rectification than the half-wave rectification. In addition, envelope extraction with the Hilbert transform produced the highest rating on subjective judgment of sound quality. CONCLUSIONS: Consistent with previous studies, the present result from the five MED-EL subjects showed that (1) the temporal envelope cues from a limited number of channels are sufficient to support high levels of phoneme and sentence recognition in quiet but not for speech recognition in a competing voice, (2) consonant recognition relies more on temporal cues while vowel recognition relies more on spectral cues, (3) spectral and temporal cues can be traded to some degree to produce similar performance in cochlear implant speech recognition, and (4) the Hilbert envelope improves both speech intelligibility and quality in cochlear implants.

Adult↗
PubMed1987

Speech perception takes precedence over nonspeech perception.

Some components of a speech signal, when made more intense, are heard simultaneously as speech and nonspeech--a form of duplex perception. At lower intensities, the speech alone is heard. Such intensity-dependent duplexity implies the existence of a phonetic mode of perception that takes precedence over auditory modes.

Adult↗
PubMed2001

The effects of age of cochlear implantation on speech perception outcomes in prelingually deaf children.

We have made a retrospective analysis on 70 prelingually deaf children (78% congenital; age range 2-15 years) followed for up to 5 years post-implant during which both closed set speech perception tests (TAC, WIPI) and open set tasks (PBK, GASP) were administered. We used a binary partitioning algorithm to optimally divide our dataset on the basis of age at implantation This technique achieves an optimal split when the heterogeneity of the data is most reduced (maximal drop in deviance). For the closed set speech perception tests (TAC and WIPI) partitioning best divided-out data at age 4.4 years. For the open set tests optimal division was at a higher age of implantation (GASP word, 5.6 years; PBK word, 8.4 years). Using these partitioning values, we have found statistically significant differences between rate of improvement of scores in the younger implanted children compared with those implanted later.

Adolescent↗
PubMed1991

Speech-perception aids for hearing-impaired people: current status and needed research. Working Group on Communication Aids for the Hearing-Impaired.

Both the overall aging of the population and its exposure to higher noise levels have increased the tendency to hearing loss and the importance of improved hearing aids for speech perception. This article reviews improvements in conventional electroacoustic hearing aids, as well as recently developed alternative classes of speech-perception aids, including surgically implanted cochlear stimulators, and vibrotactile, electrocutaneous and optical stimulating devices. It is concluded that the most effective aid for the vast majority of hearing-impaired persons is, and will remain for the immediate future, the electroacoustic hearing aid. In those cases for which no benefit is demonstrated for the electroacoustic aid, generally meaning persons with profound hearing loss, either the cochlear implant or a tactile aid may provide some improvement in the understanding of speech. In rare cases, some speech understanding in the absence of lip reading is achieved by patients with cochlear implants, for unexplained reasons. This and other pressing questions about speech processing need to be addressed by the research community if more effective aids are to be developed for the use of the 36.5 million hearing-impaired persons expected in the U.S. by the year 2050.

Aged↗
PubMedDate not supplied

Language and speech perception outcomes in hearing-impaired children with and without connexin 26 mutations.

This study addressed the question of whether a hearing loss caused by mutations in the connexin 26 gene had a significant effect on language and speech perception outcomes in children using cochlear implants or hearing aids. The families of children who had participated in two previous studies of language development were invited to participate in this genetic study. From the 52 children whose families agreed to participate, 15 children with connexin 26 mutations in both chromosomes were identified. After taking into account other factors which are known to affect language development and speech perception in children with impaired hearing, no significant differences were found between the 15 children where connexin 26 was known to be the cause of deafness and the other 37 children in the study.

Child↗
PubMed2005

Recruitment of fusiform face area associated with listening to degraded speech sounds in auditory-visual speech perception: a PET study.

For the fast and accurate cognition of external information, the human brain seems to integrate information from multi-sensory modalities. We used positron emission tomography (PET) to identify the brain areas related to auditory-visual speech perception. We measured the regional cerebral blood flow (rCBF) of young, normal volunteers during the presentation of dynamic facial movement at vocalization and during a visual control condition (visual noise), both under the two different auditory conditions of normal and degraded speech sounds. The subjects were instructed to listen carefully to the presented speech sound while keeping their eyes open and to say what they heard. The PET data showed that elevation of rCBF in the right fusiform gyrus (known as the "face area") was not significant when the subjects listened to normal speech sound accompanied by a dynamic image of the speaker's face, but was significant when degraded speech sound (filtered with a 500 Hz low-pass filter) was presented with the facial image. The results of the present study confirm the possible involvement of the fusiform face area (FFA) in auditory-visual speech perception, especially when auditory information is degraded, and suggest that visual information is interactively recruited to make up for insufficient auditory information.

Acoustic Stimulation↗